[PATCH v2 00/45] arm_mpam: Add KVM/arm64 and resctrl glue code

[PATCH v2 00/45] arm_mpam: Add KVM/arm64 and resctrl glue code

[Ben Horgan]

Hi all,

As James is otherwise engaged this version of the MPAM missing pieces comes
from me. I hope this does justice to all his hardwork. The changes that
I've brought to this version are the handling of systems with SME, some rework
of the KVM parts, a few small bug fixes and some tidying.

This may be the first time you are seeing this series as James spared some
of you as the rfc was posted during merge window.

One major departure from the previous snapshot branches referenced in the
base driver series is that the same MPAM setting are used for kernel-space
and user-space. That is, MPAM1_EL1 is set to the same value as MPAM0_EL1
rather than keeping the default value. The advantages of this are that it
is closer to the x86 model where the closid is globally applicable, all
partids are usable from user-space and user-space can't bypass MPAM
controls by doing the work in the kernel. However, this causes some
priority inversion where a high priority task waits to take a mutex held by
another whose resources are restricted by MPAM. It also adds some extra
isb(). I would be interested in opinions/data on the policy for MPAM in
kernel space, i.e how MPAM1_EL1 is set.

Change list in patches.

From James' cover letter:

This is the missing piece to make MPAM usable resctrl in user-space. This has
shed its debugfs code and the read/write 'event configuration' for the monitors
to make the series smaller.

This adds the arch code and KVM support first. I anticipate the whole thing
going via arm64, but if goes via tip instead, the an immutable branch with those
patches should be easy to do.

Generally the resctrl glue code works by picking what MPAM features it can expose
from the MPAM drive, then configuring the structs that back the resctrl helpers.
If your platform is sufficiently Xeon shaped, you should be able to get L2/L3 CPOR
bitmaps exposed via resctrl. CSU counters work if they are on/after the L3. MBWU
counters are considerably more hairy, and depend on hueristics around the topology,
and a bunch of stuff trying to emulate ABMC.
If it didn't pick what you wanted it to, please share the debug messages produced
when enabling dynamic debug and booting with:
| dyndbg="file mpam_resctrl.c +pl"

I've not found a platform that can test all the behaviours around the monitors,
so this is where I'd expect the most bugs.

The MPAM spec that describes all the system and MMIO registers can be found here:
https://developer.arm.com/documentation/ddi0598/db/?lang=en
(Ignored the 'RETIRED' warning - that is just arm moving the documentation around.
 This document has the best overview)


Based on v6.19-rc1
This series can be retrieved from:
https://gitlab.arm.com/linux-arm/linux-bh.git mpam_resctrl_glue_v2

Ben Horgan (7):
  arm_mpam: Stop using uninitialized variables in __ris_msmon_read()
  arm_mpam: Use non-atomic bitops when modifying feature bitmap
  arm64/sysreg: Add MPAMSM_EL1 register
  KVM: arm64: Preserve host MPAM configuration when changing traps
  KVM: arm64: Make MPAMSM_EL1 accesses UNDEF
  arm64: mpam: Initialise and context switch the MPAMSM_EL1 register
  KVM: arm64: Use kernel-space partid configuration for hypercalls

Dave Martin (2):
  arm_mpam: resctrl: Convert to/from MPAMs fixed-point formats
  arm_mpam: resctrl: Add kunit test for control format conversions

James Morse (31):
  arm64: mpam: Context switch the MPAM registers
  arm64: mpam: Re-initialise MPAM regs when CPU comes online
  arm64: mpam: Advertise the CPUs MPAM limits to the driver
  arm64: mpam: Add cpu_pm notifier to restore MPAM sysregs
  arm64: mpam: Add helpers to change a task or cpu's MPAM PARTID/PMG
    values
  KVM: arm64: Force guest EL1 to use user-space's partid configuration
  arm_mpam: resctrl: Add boilerplate cpuhp and domain allocation
  arm_mpam: resctrl: Sort the order of the domain lists
  arm_mpam: resctrl: Pick the caches we will use as resctrl resources
  arm_mpam: resctrl: Implement resctrl_arch_reset_all_ctrls()
  arm_mpam: resctrl: Add resctrl_arch_get_config()
  arm_mpam: resctrl: Implement helpers to update configuration
  arm_mpam: resctrl: Add plumbing against arm64 task and cpu hooks
  arm_mpam: resctrl: Add CDP emulation
  arm_mpam: resctrl: Add rmid index helpers
  arm_mpam: resctrl: Add support for 'MB' resource
  arm_mpam: resctrl: Add support for csu counters
  arm_mpam: resctrl: Pick classes for use as mbm counters
  arm_mpam: resctrl: Pre-allocate free running monitors
  arm_mpam: resctrl: Pre-allocate assignable monitors
  arm_mpam: resctrl: Add kunit test for ABMC/CDP interactions
  arm_mpam: resctrl: Add resctrl_arch_config_cntr() for ABMC use
  arm_mpam: resctrl: Allow resctrl to allocate monitors
  arm_mpam: resctrl: Add resctrl_arch_rmid_read() and
    resctrl_arch_reset_rmid()
  arm_mpam: resctrl: Add resctrl_arch_cntr_read() &
    resctrl_arch_reset_cntr()
  arm_mpam: resctrl: Update the rmid reallocation limit
  arm_mpam: resctrl: Add empty definitions for assorted resctrl
    functions
  arm64: mpam: Select ARCH_HAS_CPU_RESCTRL
  arm_mpam: resctrl: Call resctrl_init() on platforms that can support
    resctrl
  arm_mpam: Generate a configuration for min controls
  arm_mpam: Quirk CMN-650's CSU NRDY behaviour

Jiapeng Chong (1):
  arm_mpam: Remove duplicate linux/srcu.h header

Shanker Donthineni (4):
  arm_mpam: Add quirk framework
  arm_mpam: Add workaround for T241-MPAM-1
  arm_mpam: Add workaround for T241-MPAM-4
  arm_mpam: Add workaround for T241-MPAM-6

 Documentation/arch/arm64/silicon-errata.rst |    9 +
 arch/arm64/Kconfig                          |    6 +-
 arch/arm64/include/asm/el2_setup.h          |    3 +-
 arch/arm64/include/asm/mpam.h               |  104 +
 arch/arm64/include/asm/resctrl.h            |    2 +
 arch/arm64/include/asm/thread_info.h        |    3 +
 arch/arm64/kernel/Makefile                  |    1 +
 arch/arm64/kernel/cpufeature.c              |   21 +-
 arch/arm64/kernel/mpam.c                    |   58 +
 arch/arm64/kernel/process.c                 |    7 +
 arch/arm64/kvm/hyp/include/hyp/switch.h     |   12 +-
 arch/arm64/kvm/hyp/nvhe/hyp-main.c          |    5 +
 arch/arm64/kvm/hyp/vhe/sysreg-sr.c          |   11 +
 arch/arm64/kvm/sys_regs.c                   |    2 +
 arch/arm64/tools/sysreg                     |    8 +
 drivers/resctrl/Kconfig                     |    9 +-
 drivers/resctrl/Makefile                    |    1 +
 drivers/resctrl/mpam_devices.c              |  314 ++-
 drivers/resctrl/mpam_internal.h             |  128 +-
 drivers/resctrl/mpam_resctrl.c              | 1941 +++++++++++++++++++
 drivers/resctrl/test_mpam_devices.c         |   66 +
 drivers/resctrl/test_mpam_resctrl.c         |  374 ++++
 include/linux/arm_mpam.h                    |   32 +
 23 files changed, 3080 insertions(+), 37 deletions(-)
 create mode 100644 arch/arm64/include/asm/mpam.h
 create mode 100644 arch/arm64/include/asm/resctrl.h
 create mode 100644 arch/arm64/kernel/mpam.c
 create mode 100644 drivers/resctrl/mpam_resctrl.c
 create mode 100644 drivers/resctrl/test_mpam_resctrl.c

-- 
2.43.0

[PATCH v2 01/45] arm_mpam: Stop using uninitialized variables in __ris_msmon_read()

[Ben Horgan]

Dan has reported two uses of uninitialized variables in __ris_msmon_read().
If an unknown monitor type is encountered then the local variable, now, is
used uninitialized. Fix this by returning early on error. If a non-mbwu
monitor is being read then the local variable, overflow, is not initialized
but still read. Initialize it to false as overflow is not relevant for csu
monitors.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/202512091519.RBwiJcSq-lkp@intel.com/
Closes: https://lore.kernel.org/r/202512100547.N7QPYgfb-lkp@intel.com/
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 drivers/resctrl/mpam_devices.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 0b5b158e1aaf..b495d5291868 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -1072,7 +1072,7 @@ static void __ris_msmon_read(void *arg)
 	u64 now;
 	bool nrdy = false;
 	bool config_mismatch;
-	bool overflow;
+	bool overflow = false;
 	struct mon_read *m = arg;
 	struct mon_cfg *ctx = m->ctx;
 	bool reset_on_next_read = false;
@@ -1176,10 +1176,11 @@ static void __ris_msmon_read(void *arg)
 	}
 	mpam_mon_sel_unlock(msc);
 
-	if (nrdy) {
+	if (nrdy)
 		m->err = -EBUSY;
+
+	if (m->err)
 		return;
-	}
 
 	*m->val += now;
 }
-- 
2.43.0

Re: [PATCH v2 01/45] arm_mpam: Stop using uninitialized variables in __ris_msmon_read()

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:03 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> Dan has reported two uses of uninitialized variables in __ris_msmon_read().
> If an unknown monitor type is encountered then the local variable, now, is
> used uninitialized. Fix this by returning early on error. If a non-mbwu
> monitor is being read then the local variable, overflow, is not initialized
> but still read. Initialize it to false as overflow is not relevant for csu
> monitors.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> Closes: https://lore.kernel.org/r/202512091519.RBwiJcSq-lkp@intel.com/
> Closes: https://lore.kernel.org/r/202512100547.N7QPYgfb-lkp@intel.com/
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

[PATCH v2 02/45] arm_mpam: Remove duplicate linux/srcu.h header

[Ben Horgan]

From: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>

./drivers/resctrl/mpam_internal.h: linux/srcu.h is included more than once.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=27328
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Acked-by: James Morse <james.morse@arm.com>
[BH: Keep alphabetical order]
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 drivers/resctrl/mpam_internal.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index e79c3c47259c..17cdc3080d58 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -12,7 +12,6 @@
 #include <linux/jump_label.h>
 #include <linux/llist.h>
 #include <linux/mutex.h>
-#include <linux/srcu.h>
 #include <linux/spinlock.h>
 #include <linux/srcu.h>
 #include <linux/types.h>
-- 
2.43.0

Re: [PATCH v2 02/45] arm_mpam: Remove duplicate linux/srcu.h header

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:04 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
> 
> ./drivers/resctrl/mpam_internal.h: linux/srcu.h is included more than once.
> 
> Reported-by: Abaci Robot <abaci@linux.alibaba.com>
> Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=27328
> Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
> Acked-by: James Morse <james.morse@arm.com>
> [BH: Keep alphabetical order]
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

[PATCH v2 03/45] arm_mpam: Use non-atomic bitops when modifying feature bitmap

[Ben Horgan]

In the test__props_mismatch() kunit test we rely on the struct mpam_props
being packed to ensure memcmp doesn't consider packing. Making it packed
reduces the alignment of the features bitmap and so breaks a requirement
for the use of atomics. As we don't rely on the set/clear of these bits
being atomic, just make them non-atomic.

Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 drivers/resctrl/mpam_internal.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index 17cdc3080d58..aaaf31ca9210 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -200,8 +200,8 @@ struct mpam_props {
 } PACKED_FOR_KUNIT;
 
 #define mpam_has_feature(_feat, x)	test_bit(_feat, (x)->features)
-#define mpam_set_feature(_feat, x)	set_bit(_feat, (x)->features)
-#define mpam_clear_feature(_feat, x)	clear_bit(_feat, (x)->features)
+#define mpam_set_feature(_feat, x)	__set_bit(_feat, (x)->features)
+#define mpam_clear_feature(_feat, x)	__clear_bit(_feat, (x)->features)
 
 /* The values for MSMON_CFG_MBWU_FLT.RWBW */
 enum mon_filter_options {
-- 
2.43.0

Re: [PATCH v2 03/45] arm_mpam: Use non-atomic bitops when modifying feature bitmap

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:05 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> In the test__props_mismatch() kunit test we rely on the struct mpam_props
> being packed to ensure memcmp doesn't consider packing. Making it packed
> reduces the alignment of the features bitmap and so breaks a requirement
> for the use of atomics. As we don't rely on the set/clear of these bits
> being atomic, just make them non-atomic.

oh. That's a bit horrible.

Whilst I guess no one is likely to 'upgrade' these it feels odd enough that
I'd be tempted to leave a breadcrumb of a comment next to them on why
they must be the non atomic versions.

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

Jonathan


> 
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> ---
>  drivers/resctrl/mpam_internal.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
> index 17cdc3080d58..aaaf31ca9210 100644
> --- a/drivers/resctrl/mpam_internal.h
> +++ b/drivers/resctrl/mpam_internal.h
> @@ -200,8 +200,8 @@ struct mpam_props {
>  } PACKED_FOR_KUNIT;
>  
>  #define mpam_has_feature(_feat, x)	test_bit(_feat, (x)->features)
> -#define mpam_set_feature(_feat, x)	set_bit(_feat, (x)->features)
> -#define mpam_clear_feature(_feat, x)	clear_bit(_feat, (x)->features)
> +#define mpam_set_feature(_feat, x)	__set_bit(_feat, (x)->features)
> +#define mpam_clear_feature(_feat, x)	__clear_bit(_feat, (x)->features)
>  
>  /* The values for MSMON_CFG_MBWU_FLT.RWBW */
>  enum mon_filter_options {

Re: [PATCH v2 03/45] arm_mpam: Use non-atomic bitops when modifying feature bitmap

[Ben Horgan]

Hi Jonathan,

On 1/5/26 16:34, Jonathan Cameron wrote:
> On Fri, 19 Dec 2025 18:11:05 +0000
> Ben Horgan <ben.horgan@arm.com> wrote:
> 
>> In the test__props_mismatch() kunit test we rely on the struct mpam_props
>> being packed to ensure memcmp doesn't consider packing. Making it packed
>> reduces the alignment of the features bitmap and so breaks a requirement
>> for the use of atomics. As we don't rely on the set/clear of these bits
>> being atomic, just make them non-atomic.
> 
> oh. That's a bit horrible.
> 
> Whilst I guess no one is likely to 'upgrade' these it feels odd enough that
> I'd be tempted to leave a breadcrumb of a comment next to them on why
> they must be the non atomic versions.

Sure, I've added the comment:

The non-atomic get/set operations are used because if struct mpam_props
is packed, the alignment requirements for atomics aren't met.

> 
> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
> 
> Jonathan
> 
> 
>>
>> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Thanks,

Ben

[PATCH v2 04/45] arm64/sysreg: Add MPAMSM_EL1 register

[Ben Horgan]

The MPAMSM_EL1 register determines the MPAM configuration for an SMCU. Add
the register definition.

Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 arch/arm64/tools/sysreg | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm64/tools/sysreg b/arch/arm64/tools/sysreg
index 8921b51866d6..afbb55c9b038 100644
--- a/arch/arm64/tools/sysreg
+++ b/arch/arm64/tools/sysreg
@@ -5052,6 +5052,14 @@ Field	31:16	PARTID_D
 Field	15:0	PARTID_I
 EndSysreg
 
+Sysreg	MPAMSM_EL1	3	0	10	5	3
+Res0	63:48
+Field	47:40	PMG_D
+Res0	39:32
+Field	31:16	PARTID_D
+Res0	15:0
+EndSysreg
+
 Sysreg	ISR_EL1	3	0	12	1	0
 Res0	63:11
 Field	10	IS
-- 
2.43.0

Re: [PATCH v2 04/45] arm64/sysreg: Add MPAMSM_EL1 register

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:06 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> The MPAMSM_EL1 register determines the MPAM configuration for an SMCU. Add
> the register definition.
> 
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>

Matches the spec

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
> ---
>  arch/arm64/tools/sysreg | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/arch/arm64/tools/sysreg b/arch/arm64/tools/sysreg
> index 8921b51866d6..afbb55c9b038 100644
> --- a/arch/arm64/tools/sysreg
> +++ b/arch/arm64/tools/sysreg
> @@ -5052,6 +5052,14 @@ Field	31:16	PARTID_D
>  Field	15:0	PARTID_I
>  EndSysreg
>  
> +Sysreg	MPAMSM_EL1	3	0	10	5	3
> +Res0	63:48
> +Field	47:40	PMG_D
> +Res0	39:32
> +Field	31:16	PARTID_D
> +Res0	15:0
> +EndSysreg
> +
>  Sysreg	ISR_EL1	3	0	12	1	0
>  Res0	63:11
>  Field	10	IS

[PATCH v2 05/45] KVM: arm64: Preserve host MPAM configuration when changing traps

[Ben Horgan]

When kvm enables or disables MPAM traps to EL2 it clears all other bits in
MPAM2_EL2.  Notably, it clears the partition ids (PARTIDs) and performance
monitoring groups (PMGs). Avoid changing these bits in anticipation of
adding support for MPAM in the kernel. Otherwise, on a VHE system with the
host running at EL2 where MPAM2_EL2 and MPAM1_EL1 access the same register,
any attempt to use MPAM to monitor or partition resources for kernel space
would be foiled by running a KVM guest. Additionally, MPAM2_EL2.EnMPAMSM is
always set to 0 which causes MPAMSM_EL1 to always trap. Keep EnMPAMSM set
to 1 when not in a guest so that the kernel can use MPAMSM_EL1.

Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 arch/arm64/kvm/hyp/include/hyp/switch.h | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index c5d5e5b86eaf..63195275a8b8 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -269,7 +269,8 @@ static inline void __deactivate_traps_hfgxtr(struct kvm_vcpu *vcpu)
 
 static inline void  __activate_traps_mpam(struct kvm_vcpu *vcpu)
 {
-	u64 r = MPAM2_EL2_TRAPMPAM0EL1 | MPAM2_EL2_TRAPMPAM1EL1;
+	u64 clr = MPAM2_EL2_EnMPAMSM;
+	u64 set = MPAM2_EL2_TRAPMPAM0EL1 | MPAM2_EL2_TRAPMPAM1EL1;
 
 	if (!system_supports_mpam())
 		return;
@@ -279,18 +280,21 @@ static inline void  __activate_traps_mpam(struct kvm_vcpu *vcpu)
 		write_sysreg_s(MPAMHCR_EL2_TRAP_MPAMIDR_EL1, SYS_MPAMHCR_EL2);
 	} else {
 		/* From v1.1 TIDR can trap MPAMIDR, set it unconditionally */
-		r |= MPAM2_EL2_TIDR;
+		set |= MPAM2_EL2_TIDR;
 	}
 
-	write_sysreg_s(r, SYS_MPAM2_EL2);
+	sysreg_clear_set_s(SYS_MPAM2_EL2, clr, set);
 }
 
 static inline void __deactivate_traps_mpam(void)
 {
+	u64 clr = MPAM2_EL2_TRAPMPAM0EL1 | MPAM2_EL2_TRAPMPAM1EL1 | MPAM2_EL2_TIDR;
+	u64 set = MPAM2_EL2_EnMPAMSM;
+
 	if (!system_supports_mpam())
 		return;
 
-	write_sysreg_s(0, SYS_MPAM2_EL2);
+	sysreg_clear_set_s(SYS_MPAM2_EL2, clr, set);
 
 	if (system_supports_mpam_hcr())
 		write_sysreg_s(MPAMHCR_HOST_FLAGS, SYS_MPAMHCR_EL2);
-- 
2.43.0

Re: [PATCH v2 05/45] KVM: arm64: Preserve host MPAM configuration when changing traps

[Oliver Upton]

Hi Ben,

On Fri, Dec 19, 2025 at 06:11:07PM +0000, Ben Horgan wrote:
> When kvm enables or disables MPAM traps to EL2 it clears all other bits in
> MPAM2_EL2.  Notably, it clears the partition ids (PARTIDs) and performance
> monitoring groups (PMGs). Avoid changing these bits in anticipation of
> adding support for MPAM in the kernel. Otherwise, on a VHE system with the
> host running at EL2 where MPAM2_EL2 and MPAM1_EL1 access the same register,
> any attempt to use MPAM to monitor or partition resources for kernel space
> would be foiled by running a KVM guest. Additionally, MPAM2_EL2.EnMPAMSM is
> always set to 0 which causes MPAMSM_EL1 to always trap. Keep EnMPAMSM set
> to 1 when not in a guest so that the kernel can use MPAMSM_EL1.
> 
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> ---
>  arch/arm64/kvm/hyp/include/hyp/switch.h | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
> index c5d5e5b86eaf..63195275a8b8 100644
> --- a/arch/arm64/kvm/hyp/include/hyp/switch.h
> +++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
> @@ -269,7 +269,8 @@ static inline void __deactivate_traps_hfgxtr(struct kvm_vcpu *vcpu)
>  
>  static inline void  __activate_traps_mpam(struct kvm_vcpu *vcpu)
>  {
> -	u64 r = MPAM2_EL2_TRAPMPAM0EL1 | MPAM2_EL2_TRAPMPAM1EL1;
> +	u64 clr = MPAM2_EL2_EnMPAMSM;
> +	u64 set = MPAM2_EL2_TRAPMPAM0EL1 | MPAM2_EL2_TRAPMPAM1EL1;
>  
>  	if (!system_supports_mpam())
>  		return;
> @@ -279,18 +280,21 @@ static inline void  __activate_traps_mpam(struct kvm_vcpu *vcpu)
>  		write_sysreg_s(MPAMHCR_EL2_TRAP_MPAMIDR_EL1, SYS_MPAMHCR_EL2);
>  	} else {
>  		/* From v1.1 TIDR can trap MPAMIDR, set it unconditionally */
> -		r |= MPAM2_EL2_TIDR;
> +		set |= MPAM2_EL2_TIDR;
>  	}
>  
> -	write_sysreg_s(r, SYS_MPAM2_EL2);
> +	sysreg_clear_set_s(SYS_MPAM2_EL2, clr, set);

I'd recommend documenting that writes to MPAM1_EL1 are followed by an
ISB. Otherwise it isn't obvious here where context synchronization is
happening (if at all).

Thanks,
Oliver

Re: [PATCH v2 05/45] KVM: arm64: Preserve host MPAM configuration when changing traps

[Ben Horgan]

Hi Oliver,

On 12/19/25 20:01, Oliver Upton wrote:
> Hi Ben,
> 
> On Fri, Dec 19, 2025 at 06:11:07PM +0000, Ben Horgan wrote:
>> When kvm enables or disables MPAM traps to EL2 it clears all other bits in
>> MPAM2_EL2.  Notably, it clears the partition ids (PARTIDs) and performance
>> monitoring groups (PMGs). Avoid changing these bits in anticipation of
>> adding support for MPAM in the kernel. Otherwise, on a VHE system with the
>> host running at EL2 where MPAM2_EL2 and MPAM1_EL1 access the same register,
>> any attempt to use MPAM to monitor or partition resources for kernel space
>> would be foiled by running a KVM guest. Additionally, MPAM2_EL2.EnMPAMSM is
>> always set to 0 which causes MPAMSM_EL1 to always trap. Keep EnMPAMSM set
>> to 1 when not in a guest so that the kernel can use MPAMSM_EL1.
>>
>> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
>> ---
>>  arch/arm64/kvm/hyp/include/hyp/switch.h | 12 ++++++++----
>>  1 file changed, 8 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
>> index c5d5e5b86eaf..63195275a8b8 100644
>> --- a/arch/arm64/kvm/hyp/include/hyp/switch.h
>> +++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
>> @@ -269,7 +269,8 @@ static inline void __deactivate_traps_hfgxtr(struct kvm_vcpu *vcpu)
>>  
>>  static inline void  __activate_traps_mpam(struct kvm_vcpu *vcpu)
>>  {
>> -	u64 r = MPAM2_EL2_TRAPMPAM0EL1 | MPAM2_EL2_TRAPMPAM1EL1;
>> +	u64 clr = MPAM2_EL2_EnMPAMSM;
>> +	u64 set = MPAM2_EL2_TRAPMPAM0EL1 | MPAM2_EL2_TRAPMPAM1EL1;
>>  
>>  	if (!system_supports_mpam())
>>  		return;
>> @@ -279,18 +280,21 @@ static inline void  __activate_traps_mpam(struct kvm_vcpu *vcpu)
>>  		write_sysreg_s(MPAMHCR_EL2_TRAP_MPAMIDR_EL1, SYS_MPAMHCR_EL2);
>>  	} else {
>>  		/* From v1.1 TIDR can trap MPAMIDR, set it unconditionally */
>> -		r |= MPAM2_EL2_TIDR;
>> +		set |= MPAM2_EL2_TIDR;
>>  	}
>>  
>> -	write_sysreg_s(r, SYS_MPAM2_EL2);
>> +	sysreg_clear_set_s(SYS_MPAM2_EL2, clr, set);
> 
> I'd recommend documenting that writes to MPAM1_EL1 are followed by an
> ISB. Otherwise it isn't obvious here where context synchronization is
> happening (if at all).

Ok, but why are you mentioning it here?

This is just updating the traps while ensuring the partid/pmg are
unchanged. The traps are only relevant once we change exception level
and for activation they are synchronized in __guest_enter() and the eret
when returning to userspace.

> 
> Thanks,
> Oliver

Thanks,

Ben

Re: [PATCH v2 05/45] KVM: arm64: Preserve host MPAM configuration when changing traps

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:07 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> When kvm enables or disables MPAM traps to EL2 it clears all other bits in
> MPAM2_EL2.  Notably, it clears the partition ids (PARTIDs) and performance
> monitoring groups (PMGs). Avoid changing these bits in anticipation of
> adding support for MPAM in the kernel. Otherwise, on a VHE system with the
> host running at EL2 where MPAM2_EL2 and MPAM1_EL1 access the same register,
> any attempt to use MPAM to monitor or partition resources for kernel space
> would be foiled by running a KVM guest. Additionally, MPAM2_EL2.EnMPAMSM is
> always set to 0 which causes MPAMSM_EL1 to always trap. Keep EnMPAMSM set
> to 1 when not in a guest so that the kernel can use MPAMSM_EL1.
> 
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Seems to match what I'd expect from the spec, so LGTM.
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

[PATCH v2 06/45] KVM: arm64: Make MPAMSM_EL1 accesses UNDEF

[Ben Horgan]

The MPAMSM_EL1 controls the MPAM labeling for an SMCU, Streaming Mode
Compute Unit. As there is on MPAM support in kvm, make sure MPAMSM_EL1
accesses trigger an UNDEF.

The range of valid configurations for the PARTID and PMG in MPAMSM_EL1 is
not currently specified in Arm Architectural Reference Manual but the
architect has confirmed that it is intended to be the same as that for the
cpu configuration in the MPAMy_ELx registers.

Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 arch/arm64/kvm/sys_regs.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index c8fd7c6a12a1..72654ab984ee 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -3373,6 +3373,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 
 	{ SYS_DESC(SYS_MPAM1_EL1), undef_access },
 	{ SYS_DESC(SYS_MPAM0_EL1), undef_access },
+	{ SYS_DESC(SYS_MPAMSM_EL1), undef_access },
+
 	{ SYS_DESC(SYS_VBAR_EL1), access_rw, reset_val, VBAR_EL1, 0 },
 	{ SYS_DESC(SYS_DISR_EL1), NULL, reset_val, DISR_EL1, 0 },
 
-- 
2.43.0

Re: [PATCH v2 06/45] KVM: arm64: Make MPAMSM_EL1 accesses UNDEF

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:08 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> The MPAMSM_EL1 controls the MPAM labeling for an SMCU, Streaming Mode
> Compute Unit. As there is on MPAM support in kvm, make sure MPAMSM_EL1
> accesses trigger an UNDEF.
> 
> The range of valid configurations for the PARTID and PMG in MPAMSM_EL1 is
> not currently specified in Arm Architectural Reference Manual but the
> architect has confirmed that it is intended to be the same as that for the
> cpu configuration in the MPAMy_ELx registers.

Good to know but I'm not seeing why it matters in this patch. Perhaps
a little more on that?

> 
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> ---
>  arch/arm64/kvm/sys_regs.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index c8fd7c6a12a1..72654ab984ee 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -3373,6 +3373,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  
>  	{ SYS_DESC(SYS_MPAM1_EL1), undef_access },
>  	{ SYS_DESC(SYS_MPAM0_EL1), undef_access },
> +	{ SYS_DESC(SYS_MPAMSM_EL1), undef_access },
> +
>  	{ SYS_DESC(SYS_VBAR_EL1), access_rw, reset_val, VBAR_EL1, 0 },
>  	{ SYS_DESC(SYS_DISR_EL1), NULL, reset_val, DISR_EL1, 0 },
>  

Re: [PATCH v2 06/45] KVM: arm64: Make MPAMSM_EL1 accesses UNDEF

[Ben Horgan]

Hi Jonathan,

On 1/5/26 16:47, Jonathan Cameron wrote:
> On Fri, 19 Dec 2025 18:11:08 +0000
> Ben Horgan <ben.horgan@arm.com> wrote:
> 
>> The MPAMSM_EL1 controls the MPAM labeling for an SMCU, Streaming Mode
>> Compute Unit. As there is on MPAM support in kvm, make sure MPAMSM_EL1
>> accesses trigger an UNDEF.
>>
>> The range of valid configurations for the PARTID and PMG in MPAMSM_EL1 is
>> not currently specified in Arm Architectural Reference Manual but the
>> architect has confirmed that it is intended to be the same as that for the
>> cpu configuration in the MPAMy_ELx registers.
> 
> Good to know but I'm not seeing why it matters in this patch. Perhaps
> a little more on that?

Hmmm, yes. This paragraph should go with patch 11 where we start setting
MPAMSM_EL1 with the same value as MPAM0_EL1 and MPAM1_EL1.

> 
>>
>> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> 
> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
> 
>> ---
>>  arch/arm64/kvm/sys_regs.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>> index c8fd7c6a12a1..72654ab984ee 100644
>> --- a/arch/arm64/kvm/sys_regs.c
>> +++ b/arch/arm64/kvm/sys_regs.c
>> @@ -3373,6 +3373,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>>  
>>  	{ SYS_DESC(SYS_MPAM1_EL1), undef_access },
>>  	{ SYS_DESC(SYS_MPAM0_EL1), undef_access },
>> +	{ SYS_DESC(SYS_MPAMSM_EL1), undef_access },
>> +
>>  	{ SYS_DESC(SYS_VBAR_EL1), access_rw, reset_val, VBAR_EL1, 0 },
>>  	{ SYS_DESC(SYS_DISR_EL1), NULL, reset_val, DISR_EL1, 0 },
>>  
> 

Thanks,

Ben

[PATCH v2 07/45] arm64: mpam: Context switch the MPAM registers

[Ben Horgan]

From: James Morse <james.morse@arm.com>

MPAM allows traffic in the SoC to be labeled by the OS, these labels are
used to apply policy in caches and bandwidth regulators, and to monitor
traffic in the SoC. The label is made up of a PARTID and PMG value. The x86
equivalent calls these CLOSID and RMID, but they don't map precisely.

MPAM has two CPU system registers that is used to hold the PARTID and PMG
values that traffic generated at each exception level will use. These can
be set per-task by the resctrl file system. (resctrl is the defacto
interface for controlling this stuff).

Add a helper to switch this.

struct task_struct's separate CLOSID and RMID fields are insufficient to
implement resctrl using MPAM, as resctrl can change the PARTID (CLOSID) and
PMG (sort of like the RMID) separately. On x86, the rmid is an independent
number, so a race that writes a mismatched closid and rmid into hardware is
benign. On arm64, the pmg bits extend the partid.
(i.e. partid-5 has a pmg-0 that is not the same as partid-6's pmg-0).  In
this case, mismatching the values will 'dirty' a pmg value that resctrl
believes is clean, and is not tracking with its 'limbo' code.

To avoid this, the partid and pmg are always read and written as a pair.
Instead of making struct task_struct's closid and rmid fields an
endian-unsafe union, add the value to struct thread_info and always use
READ_ONCE()/WRITE_ONCE() when accessing this field.

Resctrl allows a per-cpu 'default' value to be set, this overrides the
values when scheduling a task in the default control-group, which has
PARTID 0. The way 'code data prioritisation' gets emulated means the
register value for the default group needs to be a variable.

The current system register value is kept in a per-cpu variable to avoid
writing to the system register if the value isn't going to change.  Writes
to this register may reset the hardware state for regulating bandwidth.

Finally, there is no reason to context switch these registers unless there
is a driver changing the values in struct task_struct. Hide the whole thing
behind a static key. This also allows the driver to disable MPAM in
response to errors reported by hardware. Move the existing static key to
belong to the arch code, as in the future the MPAM driver may become a
loadable module.

All this should depend on whether there is an MPAM driver, hide it behind
CONFIG_ARM64_MPAM.

CC: Amit Singh Tomar <amitsinght@marvell.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
CONFIG_MPAM -> CONFIG_ARM64_MPAM in commit message
Remove extra DECLARE_STATIC_KEY_FALSE
Function name in comment, __mpam_sched_in() -> mpam_thread_switch()
Remove unused headers
Expand comment (Jonathan)
---
 arch/arm64/Kconfig                   |  2 +
 arch/arm64/include/asm/mpam.h        | 73 ++++++++++++++++++++++++++++
 arch/arm64/include/asm/thread_info.h |  3 ++
 arch/arm64/kernel/Makefile           |  1 +
 arch/arm64/kernel/mpam.c             | 13 +++++
 arch/arm64/kernel/process.c          |  7 +++
 drivers/resctrl/mpam_devices.c       |  2 -
 drivers/resctrl/mpam_internal.h      |  4 +-
 8 files changed, 101 insertions(+), 4 deletions(-)
 create mode 100644 arch/arm64/include/asm/mpam.h
 create mode 100644 arch/arm64/kernel/mpam.c

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 93173f0a09c7..cdcc5b76a110 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -2049,6 +2049,8 @@ config ARM64_MPAM
 
 	  MPAM is exposed to user-space via the resctrl pseudo filesystem.
 
+	  This option enables the extra context switch code.
+
 endmenu # "ARMv8.4 architectural features"
 
 menu "ARMv8.5 architectural features"
diff --git a/arch/arm64/include/asm/mpam.h b/arch/arm64/include/asm/mpam.h
new file mode 100644
index 000000000000..2ab3dca6977c
--- /dev/null
+++ b/arch/arm64/include/asm/mpam.h
@@ -0,0 +1,73 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2025 Arm Ltd. */
+
+#ifndef __ASM__MPAM_H
+#define __ASM__MPAM_H
+
+#include <linux/jump_label.h>
+#include <linux/percpu.h>
+#include <linux/sched.h>
+
+#include <asm/sysreg.h>
+
+DECLARE_STATIC_KEY_FALSE(mpam_enabled);
+DECLARE_PER_CPU(u64, arm64_mpam_default);
+DECLARE_PER_CPU(u64, arm64_mpam_current);
+
+/*
+ * The value of the MPAM0_EL1 sysreg when a task is in resctrl's default group.
+ * This is used by the context switch code to use the resctrl CPU property
+ * instead. The value is modified when CDP is enabled/disabled by mounting
+ * the resctrl filesystem.
+ */
+extern u64 arm64_mpam_global_default;
+
+/*
+ * The resctrl filesystem writes to the partid/pmg values for threads and CPUs,
+ * which may race with reads in mpam_thread_switch(). Ensure only one of the old
+ * or new values are used. Particular care should be taken with the pmg field as
+ * mpam_thread_switch() may read a partid and pmg that don't match, causing this
+ * value to be stored with cache allocations, despite being considered 'free' by
+ * resctrl.
+ *
+ * A value in struct thread_info is used instead of struct task_struct as the
+ * cpu's u64 register format is used. In struct task_struct there are two u32,
+ * rmid and closid for the x86 case, but as we can't use them here do something
+ * else. Creating a union would mean only accesses from the created u64 would be
+ * endian safe and so be less clear.
+ */
+static inline u64 mpam_get_regval(struct task_struct *tsk)
+{
+#ifdef CONFIG_ARM64_MPAM
+	return READ_ONCE(task_thread_info(tsk)->mpam_partid_pmg);
+#else
+	return 0;
+#endif
+}
+
+static inline void mpam_thread_switch(struct task_struct *tsk)
+{
+	u64 oldregval;
+	int cpu = smp_processor_id();
+	u64 regval = mpam_get_regval(tsk);
+
+	if (!IS_ENABLED(CONFIG_ARM64_MPAM) ||
+	    !static_branch_likely(&mpam_enabled))
+		return;
+
+	if (regval == READ_ONCE(arm64_mpam_global_default))
+		regval = READ_ONCE(per_cpu(arm64_mpam_default, cpu));
+
+	oldregval = READ_ONCE(per_cpu(arm64_mpam_current, cpu));
+	if (oldregval == regval)
+		return;
+
+	write_sysreg_s(regval, SYS_MPAM1_EL1);
+	isb();
+
+	/* Synchronising the EL0 write is left until the ERET to EL0 */
+	write_sysreg_s(regval, SYS_MPAM0_EL1);
+
+	WRITE_ONCE(per_cpu(arm64_mpam_current, cpu), regval);
+}
+#endif /* __ASM__MPAM_H */
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index a803b887b0b4..fc801a26ff9e 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -41,6 +41,9 @@ struct thread_info {
 #ifdef CONFIG_SHADOW_CALL_STACK
 	void			*scs_base;
 	void			*scs_sp;
+#endif
+#ifdef CONFIG_ARM64_MPAM
+	u64			mpam_partid_pmg;
 #endif
 	u32			cpu;
 };
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 76f32e424065..15979f366519 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -67,6 +67,7 @@ obj-$(CONFIG_CRASH_DUMP)		+= crash_dump.o
 obj-$(CONFIG_VMCORE_INFO)		+= vmcore_info.o
 obj-$(CONFIG_ARM_SDE_INTERFACE)		+= sdei.o
 obj-$(CONFIG_ARM64_PTR_AUTH)		+= pointer_auth.o
+obj-$(CONFIG_ARM64_MPAM)		+= mpam.o
 obj-$(CONFIG_ARM64_MTE)			+= mte.o
 obj-y					+= vdso-wrap.o
 obj-$(CONFIG_COMPAT_VDSO)		+= vdso32-wrap.o
diff --git a/arch/arm64/kernel/mpam.c b/arch/arm64/kernel/mpam.c
new file mode 100644
index 000000000000..9866d2ca0faa
--- /dev/null
+++ b/arch/arm64/kernel/mpam.c
@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2025 Arm Ltd. */
+
+#include <asm/mpam.h>
+
+#include <linux/jump_label.h>
+#include <linux/percpu.h>
+
+DEFINE_STATIC_KEY_FALSE(mpam_enabled);
+DEFINE_PER_CPU(u64, arm64_mpam_default);
+DEFINE_PER_CPU(u64, arm64_mpam_current);
+
+u64 arm64_mpam_global_default;
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index fba7ca102a8c..b510c0699313 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -51,6 +51,7 @@
 #include <asm/fpsimd.h>
 #include <asm/gcs.h>
 #include <asm/mmu_context.h>
+#include <asm/mpam.h>
 #include <asm/mte.h>
 #include <asm/processor.h>
 #include <asm/pointer_auth.h>
@@ -737,6 +738,12 @@ struct task_struct *__switch_to(struct task_struct *prev,
 	if (prev->thread.sctlr_user != next->thread.sctlr_user)
 		update_sctlr_el1(next->thread.sctlr_user);
 
+	/*
+	 * MPAM thread switch happens after the DSB to ensure prev's accesses
+	 * use prev's MPAM settings.
+	 */
+	mpam_thread_switch(next);
+
 	/* the actual thread switch */
 	last = cpu_switch_to(prev, next);
 
diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index b495d5291868..860181266b15 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -29,8 +29,6 @@
 
 #include "mpam_internal.h"
 
-DEFINE_STATIC_KEY_FALSE(mpam_enabled); /* This moves to arch code */
-
 /*
  * mpam_list_lock protects the SRCU lists when writing. Once the
  * mpam_enabled key is enabled these lists are read-only,
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index aaaf31ca9210..e6e7ba4342d6 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -16,12 +16,12 @@
 #include <linux/srcu.h>
 #include <linux/types.h>
 
+#include <asm/mpam.h>
+
 #define MPAM_MSC_MAX_NUM_RIS	16
 
 struct platform_device;
 
-DECLARE_STATIC_KEY_FALSE(mpam_enabled);
-
 #ifdef CONFIG_MPAM_KUNIT_TEST
 #define PACKED_FOR_KUNIT __packed
 #else
-- 
2.43.0

Re: [PATCH v2 07/45] arm64: mpam: Context switch the MPAM registers

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:09 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> MPAM allows traffic in the SoC to be labeled by the OS, these labels are
> used to apply policy in caches and bandwidth regulators, and to monitor
> traffic in the SoC. The label is made up of a PARTID and PMG value. The x86
> equivalent calls these CLOSID and RMID, but they don't map precisely.
> 
> MPAM has two CPU system registers that is used to hold the PARTID and PMG
> values that traffic generated at each exception level will use. These can
> be set per-task by the resctrl file system. (resctrl is the defacto
> interface for controlling this stuff).
> 
> Add a helper to switch this.
> 
> struct task_struct's separate CLOSID and RMID fields are insufficient to
> implement resctrl using MPAM, as resctrl can change the PARTID (CLOSID) and
> PMG (sort of like the RMID) separately. On x86, the rmid is an independent
> number, so a race that writes a mismatched closid and rmid into hardware is
> benign. On arm64, the pmg bits extend the partid.
> (i.e. partid-5 has a pmg-0 that is not the same as partid-6's pmg-0).  In
> this case, mismatching the values will 'dirty' a pmg value that resctrl
> believes is clean, and is not tracking with its 'limbo' code.
> 
> To avoid this, the partid and pmg are always read and written as a pair.
> Instead of making struct task_struct's closid and rmid fields an
> endian-unsafe union, add the value to struct thread_info and always use
> READ_ONCE()/WRITE_ONCE() when accessing this field.
I'm still hammering on this one ;)

The comment below is better way of putting that it would basically leave
some fields that look like they can be used which can't. Given they
are under ifdef CONFIG_X86_CPU_RESCTRL anyway it would be very odd
to use a union. Would just be a new appropriately ifdef protected variable
right next to them in the file.  I'd be tempted to just drop the bit
about union and say why it makes sense to instead put it in
struct thread_info (basically because it's arch specific and we can
avoid even more ifdef mess?)


> 
> Resctrl allows a per-cpu 'default' value to be set, this overrides the
> values when scheduling a task in the default control-group, which has
> PARTID 0. The way 'code data prioritisation' gets emulated means the
> register value for the default group needs to be a variable.
> 
> The current system register value is kept in a per-cpu variable to avoid
> writing to the system register if the value isn't going to change.  Writes
> to this register may reset the hardware state for regulating bandwidth.
> 
> Finally, there is no reason to context switch these registers unless there
> is a driver changing the values in struct task_struct. Hide the whole thing
> behind a static key. This also allows the driver to disable MPAM in
> response to errors reported by hardware. Move the existing static key to
> belong to the arch code, as in the future the MPAM driver may become a
> loadable module.
> 
> All this should depend on whether there is an MPAM driver, hide it behind
> CONFIG_ARM64_MPAM.
> 
> CC: Amit Singh Tomar <amitsinght@marvell.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> ---
> CONFIG_MPAM -> CONFIG_ARM64_MPAM in commit message
> Remove extra DECLARE_STATIC_KEY_FALSE
> Function name in comment, __mpam_sched_in() -> mpam_thread_switch()
> Remove unused headers
> Expand comment (Jonathan)
> ---
>  arch/arm64/Kconfig                   |  2 +
>  arch/arm64/include/asm/mpam.h        | 73 ++++++++++++++++++++++++++++
>  arch/arm64/include/asm/thread_info.h |  3 ++
>  arch/arm64/kernel/Makefile           |  1 +
>  arch/arm64/kernel/mpam.c             | 13 +++++
>  arch/arm64/kernel/process.c          |  7 +++
>  drivers/resctrl/mpam_devices.c       |  2 -
>  drivers/resctrl/mpam_internal.h      |  4 +-
>  8 files changed, 101 insertions(+), 4 deletions(-)
>  create mode 100644 arch/arm64/include/asm/mpam.h
>  create mode 100644 arch/arm64/kernel/mpam.c
> 

> diff --git a/arch/arm64/include/asm/mpam.h b/arch/arm64/include/asm/mpam.h
> new file mode 100644
> index 000000000000..2ab3dca6977c
> --- /dev/null
> +++ b/arch/arm64/include/asm/mpam.h

> +/*
> + * The resctrl filesystem writes to the partid/pmg values for threads and CPUs,
> + * which may race with reads in mpam_thread_switch(). Ensure only one of the old
> + * or new values are used. Particular care should be taken with the pmg field as
> + * mpam_thread_switch() may read a partid and pmg that don't match, causing this
> + * value to be stored with cache allocations, despite being considered 'free' by
> + * resctrl.
> + *
> + * A value in struct thread_info is used instead of struct task_struct as the
> + * cpu's u64 register format is used. In struct task_struct there are two u32,
> + * rmid and closid for the x86 case, but as we can't use them here do something
> + * else. Creating a union would mean only accesses from the created u64 would be
> + * endian safe and so be less clear.

I'd just put this as something:
  * The closid and rmid in task_struct can't be directly reused as a u64 is needed.
  * As such, a suitable variable in struct thread_info is used instead with the
  * benefit of that being clearly an architecture specific location.

or be more cynical and keep it for the patch description only. To me location
of this u64 doesn't really feel like a design decision we need to record for the ages.

With something like the suggested text, or the paragraph just dropped
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> + */
> +static inline u64 mpam_get_regval(struct task_struct *tsk)
> +{
> +#ifdef CONFIG_ARM64_MPAM
> +	return READ_ONCE(task_thread_info(tsk)->mpam_partid_pmg);
> +#else
> +	return 0;
> +#endif
> +}

Re: [PATCH v2 07/45] arm64: mpam: Context switch the MPAM registers

[Ben Horgan]

Hi Jonathan,

On 1/5/26 17:04, Jonathan Cameron wrote:
> On Fri, 19 Dec 2025 18:11:09 +0000
> Ben Horgan <ben.horgan@arm.com> wrote:
> 
>> From: James Morse <james.morse@arm.com>
>>
>> MPAM allows traffic in the SoC to be labeled by the OS, these labels are
>> used to apply policy in caches and bandwidth regulators, and to monitor
>> traffic in the SoC. The label is made up of a PARTID and PMG value. The x86
>> equivalent calls these CLOSID and RMID, but they don't map precisely.
>>
>> MPAM has two CPU system registers that is used to hold the PARTID and PMG
>> values that traffic generated at each exception level will use. These can
>> be set per-task by the resctrl file system. (resctrl is the defacto
>> interface for controlling this stuff).
>>
>> Add a helper to switch this.
>>
>> struct task_struct's separate CLOSID and RMID fields are insufficient to
>> implement resctrl using MPAM, as resctrl can change the PARTID (CLOSID) and
>> PMG (sort of like the RMID) separately. On x86, the rmid is an independent
>> number, so a race that writes a mismatched closid and rmid into hardware is
>> benign. On arm64, the pmg bits extend the partid.
>> (i.e. partid-5 has a pmg-0 that is not the same as partid-6's pmg-0).  In
>> this case, mismatching the values will 'dirty' a pmg value that resctrl
>> believes is clean, and is not tracking with its 'limbo' code.
>>
>> To avoid this, the partid and pmg are always read and written as a pair.
>> Instead of making struct task_struct's closid and rmid fields an
>> endian-unsafe union, add the value to struct thread_info and always use
>> READ_ONCE()/WRITE_ONCE() when accessing this field.
> I'm still hammering on this one ;)
> 
> The comment below is better way of putting that it would basically leave
> some fields that look like they can be used which can't. Given they
> are under ifdef CONFIG_X86_CPU_RESCTRL anyway it would be very odd
> to use a union. Would just be a new appropriately ifdef protected variable
> right next to them in the file.  I'd be tempted to just drop the bit
> about union and say why it makes sense to instead put it in
> struct thread_info (basically because it's arch specific and we can
> avoid even more ifdef mess?)
> 
> 
>>
>> Resctrl allows a per-cpu 'default' value to be set, this overrides the
>> values when scheduling a task in the default control-group, which has
>> PARTID 0. The way 'code data prioritisation' gets emulated means the
>> register value for the default group needs to be a variable.
>>
>> The current system register value is kept in a per-cpu variable to avoid
>> writing to the system register if the value isn't going to change.  Writes
>> to this register may reset the hardware state for regulating bandwidth.
>>
>> Finally, there is no reason to context switch these registers unless there
>> is a driver changing the values in struct task_struct. Hide the whole thing
>> behind a static key. This also allows the driver to disable MPAM in
>> response to errors reported by hardware. Move the existing static key to
>> belong to the arch code, as in the future the MPAM driver may become a
>> loadable module.
>>
>> All this should depend on whether there is an MPAM driver, hide it behind
>> CONFIG_ARM64_MPAM.
>>
>> CC: Amit Singh Tomar <amitsinght@marvell.com>
>> Signed-off-by: James Morse <james.morse@arm.com>
>> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
>> ---
>> CONFIG_MPAM -> CONFIG_ARM64_MPAM in commit message
>> Remove extra DECLARE_STATIC_KEY_FALSE
>> Function name in comment, __mpam_sched_in() -> mpam_thread_switch()
>> Remove unused headers
>> Expand comment (Jonathan)
>> ---
>>  arch/arm64/Kconfig                   |  2 +
>>  arch/arm64/include/asm/mpam.h        | 73 ++++++++++++++++++++++++++++
>>  arch/arm64/include/asm/thread_info.h |  3 ++
>>  arch/arm64/kernel/Makefile           |  1 +
>>  arch/arm64/kernel/mpam.c             | 13 +++++
>>  arch/arm64/kernel/process.c          |  7 +++
>>  drivers/resctrl/mpam_devices.c       |  2 -
>>  drivers/resctrl/mpam_internal.h      |  4 +-
>>  8 files changed, 101 insertions(+), 4 deletions(-)
>>  create mode 100644 arch/arm64/include/asm/mpam.h
>>  create mode 100644 arch/arm64/kernel/mpam.c
>>
> 
>> diff --git a/arch/arm64/include/asm/mpam.h b/arch/arm64/include/asm/mpam.h
>> new file mode 100644
>> index 000000000000..2ab3dca6977c
>> --- /dev/null
>> +++ b/arch/arm64/include/asm/mpam.h
> 
>> +/*
>> + * The resctrl filesystem writes to the partid/pmg values for threads and CPUs,
>> + * which may race with reads in mpam_thread_switch(). Ensure only one of the old
>> + * or new values are used. Particular care should be taken with the pmg field as
>> + * mpam_thread_switch() may read a partid and pmg that don't match, causing this
>> + * value to be stored with cache allocations, despite being considered 'free' by
>> + * resctrl.
>> + *
>> + * A value in struct thread_info is used instead of struct task_struct as the
>> + * cpu's u64 register format is used. In struct task_struct there are two u32,
>> + * rmid and closid for the x86 case, but as we can't use them here do something
>> + * else. Creating a union would mean only accesses from the created u64 would be
>> + * endian safe and so be less clear.
> 
> I'd just put this as something:
>   * The closid and rmid in task_struct can't be directly reused as a u64 is needed.
>   * As such, a suitable variable in struct thread_info is used instead with the
>   * benefit of that being clearly an architecture specific location.
> 
> or be more cynical and keep it for the patch description only. To me location
> of this u64 doesn't really feel like a design decision we need to record for the ages.
> 
> With something like the suggested text, or the paragraph just dropped
> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

Thanks! I've just dropped this comment as it seems like more trouble
than it's worth and updated the paragraph in the commit message to read:

"To avoid this, the partid and pmg are always read and written as a
pair. This requires a new u64 field. In struct task_struct there are two
u32, rmid and closid for the x86 case, but as we can't use them here do
something else. Add this new field, mpam_partid_pmg, to struct
thread_info to avoid adding more architecture specific code to struct
task_struct. Always use READ_ONCE()/WRITE_ONCE() when accessing this field."

> 
>> + */
>> +static inline u64 mpam_get_regval(struct task_struct *tsk)
>> +{
>> +#ifdef CONFIG_ARM64_MPAM
>> +	return READ_ONCE(task_thread_info(tsk)->mpam_partid_pmg);
>> +#else
>> +	return 0;
>> +#endif
>> +}
> 
> 

Thanks,

Ben

Re: [PATCH v2 07/45] arm64: mpam: Context switch the MPAM registers

[Jonathan Cameron]

On Tue, 6 Jan 2026 11:14:50 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> Hi Jonathan,
> 
> On 1/5/26 17:04, Jonathan Cameron wrote:
> > On Fri, 19 Dec 2025 18:11:09 +0000
> > Ben Horgan <ben.horgan@arm.com> wrote:
> >   
> >> From: James Morse <james.morse@arm.com>
> >>
> >> MPAM allows traffic in the SoC to be labeled by the OS, these labels are
> >> used to apply policy in caches and bandwidth regulators, and to monitor
> >> traffic in the SoC. The label is made up of a PARTID and PMG value. The x86
> >> equivalent calls these CLOSID and RMID, but they don't map precisely.
> >>
> >> MPAM has two CPU system registers that is used to hold the PARTID and PMG
> >> values that traffic generated at each exception level will use. These can
> >> be set per-task by the resctrl file system. (resctrl is the defacto
> >> interface for controlling this stuff).
> >>
> >> Add a helper to switch this.
> >>
> >> struct task_struct's separate CLOSID and RMID fields are insufficient to
> >> implement resctrl using MPAM, as resctrl can change the PARTID (CLOSID) and
> >> PMG (sort of like the RMID) separately. On x86, the rmid is an independent
> >> number, so a race that writes a mismatched closid and rmid into hardware is
> >> benign. On arm64, the pmg bits extend the partid.
> >> (i.e. partid-5 has a pmg-0 that is not the same as partid-6's pmg-0).  In
> >> this case, mismatching the values will 'dirty' a pmg value that resctrl
> >> believes is clean, and is not tracking with its 'limbo' code.
> >>
> >> To avoid this, the partid and pmg are always read and written as a pair.
> >> Instead of making struct task_struct's closid and rmid fields an
> >> endian-unsafe union, add the value to struct thread_info and always use
> >> READ_ONCE()/WRITE_ONCE() when accessing this field.  
> > I'm still hammering on this one ;)
> > 
> > The comment below is better way of putting that it would basically leave
> > some fields that look like they can be used which can't. Given they
> > are under ifdef CONFIG_X86_CPU_RESCTRL anyway it would be very odd
> > to use a union. Would just be a new appropriately ifdef protected variable
> > right next to them in the file.  I'd be tempted to just drop the bit
> > about union and say why it makes sense to instead put it in
> > struct thread_info (basically because it's arch specific and we can
> > avoid even more ifdef mess?)
> > 
> >   
> >>
> >> Resctrl allows a per-cpu 'default' value to be set, this overrides the
> >> values when scheduling a task in the default control-group, which has
> >> PARTID 0. The way 'code data prioritisation' gets emulated means the
> >> register value for the default group needs to be a variable.
> >>
> >> The current system register value is kept in a per-cpu variable to avoid
> >> writing to the system register if the value isn't going to change.  Writes
> >> to this register may reset the hardware state for regulating bandwidth.
> >>
> >> Finally, there is no reason to context switch these registers unless there
> >> is a driver changing the values in struct task_struct. Hide the whole thing
> >> behind a static key. This also allows the driver to disable MPAM in
> >> response to errors reported by hardware. Move the existing static key to
> >> belong to the arch code, as in the future the MPAM driver may become a
> >> loadable module.
> >>
> >> All this should depend on whether there is an MPAM driver, hide it behind
> >> CONFIG_ARM64_MPAM.
> >>
> >> CC: Amit Singh Tomar <amitsinght@marvell.com>
> >> Signed-off-by: James Morse <james.morse@arm.com>
> >> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> >> ---
> >> CONFIG_MPAM -> CONFIG_ARM64_MPAM in commit message
> >> Remove extra DECLARE_STATIC_KEY_FALSE
> >> Function name in comment, __mpam_sched_in() -> mpam_thread_switch()
> >> Remove unused headers
> >> Expand comment (Jonathan)
> >> ---
> >>  arch/arm64/Kconfig                   |  2 +
> >>  arch/arm64/include/asm/mpam.h        | 73 ++++++++++++++++++++++++++++
> >>  arch/arm64/include/asm/thread_info.h |  3 ++
> >>  arch/arm64/kernel/Makefile           |  1 +
> >>  arch/arm64/kernel/mpam.c             | 13 +++++
> >>  arch/arm64/kernel/process.c          |  7 +++
> >>  drivers/resctrl/mpam_devices.c       |  2 -
> >>  drivers/resctrl/mpam_internal.h      |  4 +-
> >>  8 files changed, 101 insertions(+), 4 deletions(-)
> >>  create mode 100644 arch/arm64/include/asm/mpam.h
> >>  create mode 100644 arch/arm64/kernel/mpam.c
> >>  
> >   
> >> diff --git a/arch/arm64/include/asm/mpam.h b/arch/arm64/include/asm/mpam.h
> >> new file mode 100644
> >> index 000000000000..2ab3dca6977c
> >> --- /dev/null
> >> +++ b/arch/arm64/include/asm/mpam.h  
> >   
> >> +/*
> >> + * The resctrl filesystem writes to the partid/pmg values for threads and CPUs,
> >> + * which may race with reads in mpam_thread_switch(). Ensure only one of the old
> >> + * or new values are used. Particular care should be taken with the pmg field as
> >> + * mpam_thread_switch() may read a partid and pmg that don't match, causing this
> >> + * value to be stored with cache allocations, despite being considered 'free' by
> >> + * resctrl.
> >> + *
> >> + * A value in struct thread_info is used instead of struct task_struct as the
> >> + * cpu's u64 register format is used. In struct task_struct there are two u32,
> >> + * rmid and closid for the x86 case, but as we can't use them here do something
> >> + * else. Creating a union would mean only accesses from the created u64 would be
> >> + * endian safe and so be less clear.  
> > 
> > I'd just put this as something:
> >   * The closid and rmid in task_struct can't be directly reused as a u64 is needed.
> >   * As such, a suitable variable in struct thread_info is used instead with the
> >   * benefit of that being clearly an architecture specific location.
> > 
> > or be more cynical and keep it for the patch description only. To me location
> > of this u64 doesn't really feel like a design decision we need to record for the ages.
> > 
> > With something like the suggested text, or the paragraph just dropped
> > Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>  
> 
> Thanks! I've just dropped this comment as it seems like more trouble
> than it's worth and updated the paragraph in the commit message to read:
> 
> "To avoid this, the partid and pmg are always read and written as a
> pair. This requires a new u64 field. In struct task_struct there are two
> u32, rmid and closid for the x86 case, but as we can't use them here do
> something else. Add this new field, mpam_partid_pmg, to struct
> thread_info to avoid adding more architecture specific code to struct
> task_struct. Always use READ_ONCE()/WRITE_ONCE() when accessing this field."
LGTM

> 
> >   
> >> + */
> >> +static inline u64 mpam_get_regval(struct task_struct *tsk)
> >> +{
> >> +#ifdef CONFIG_ARM64_MPAM
> >> +	return READ_ONCE(task_thread_info(tsk)->mpam_partid_pmg);
> >> +#else
> >> +	return 0;
> >> +#endif
> >> +}  
> > 
> >   
> 
> Thanks,
> 
> Ben
> 
> 

[PATCH v2 08/45] arm64: mpam: Re-initialise MPAM regs when CPU comes online

[Ben Horgan]

From: James Morse <james.morse@arm.com>

Now that the MPAM system registers are expected to have values that change,
reprogram them based on the previous value when a CPU is brought online.

Previously MPAM's 'default PARTID' of 0 was always used for MPAM in
kernel-space as this is the PARTID that hardware guarantees to
reset. Because there are a limited number of PARTID, this value is exposed
to user-space, meaning resctrl changes to the resctrl default group would
also affect kernel threads.  Instead, use the task's PARTID value for
kernel work on behalf of user-space too. The default of 0 is kept for both
user-space and kernel-space when MPAM is not enabled.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Changes since rfc:
CONFIG_MPAM -> CONFIG_ARM64_MPAM
Check mpam_enabled
Comment about relying on ERET for synchronisation
Update commit message
---
 arch/arm64/kernel/cpufeature.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index c840a93b9ef9..0cdfb3728f43 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -86,6 +86,7 @@
 #include <asm/kvm_host.h>
 #include <asm/mmu.h>
 #include <asm/mmu_context.h>
+#include <asm/mpam.h>
 #include <asm/mte.h>
 #include <asm/hypervisor.h>
 #include <asm/processor.h>
@@ -2483,13 +2484,17 @@ test_has_mpam(const struct arm64_cpu_capabilities *entry, int scope)
 static void
 cpu_enable_mpam(const struct arm64_cpu_capabilities *entry)
 {
-	/*
-	 * Access by the kernel (at EL1) should use the reserved PARTID
-	 * which is configured unrestricted. This avoids priority-inversion
-	 * where latency sensitive tasks have to wait for a task that has
-	 * been throttled to release the lock.
-	 */
-	write_sysreg_s(0, SYS_MPAM1_EL1);
+	int cpu = smp_processor_id();
+	u64 regval = 0;
+
+	if (IS_ENABLED(CONFIG_ARM64_MPAM) && static_branch_likely(&mpam_enabled))
+		regval = READ_ONCE(per_cpu(arm64_mpam_current, cpu));
+
+	write_sysreg_s(regval, SYS_MPAM1_EL1);
+	isb();
+
+	/* Synchronising the EL0 write is left until the ERET to EL0 */
+	write_sysreg_s(regval, SYS_MPAM0_EL1);
 }
 
 static bool
-- 
2.43.0

Re: [PATCH v2 08/45] arm64: mpam: Re-initialise MPAM regs when CPU comes online

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:10 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> Now that the MPAM system registers are expected to have values that change,
> reprogram them based on the previous value when a CPU is brought online.
> 
> Previously MPAM's 'default PARTID' of 0 was always used for MPAM in
> kernel-space as this is the PARTID that hardware guarantees to
> reset. Because there are a limited number of PARTID, this value is exposed
> to user-space, meaning resctrl changes to the resctrl default group would
> also affect kernel threads.  Instead, use the task's PARTID value for
> kernel work on behalf of user-space too. The default of 0 is kept for both
> user-space and kernel-space when MPAM is not enabled.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

[PATCH v2 09/45] arm64: mpam: Advertise the CPUs MPAM limits to the driver

[Ben Horgan]

From: James Morse <james.morse@arm.com>

Requestors need to populate the MPAM fields for any traffic they send on
the interconnect. For the CPUs these values are taken from the
corresponding MPAMy_ELx register. Each requestor may have a limit on the
largest PARTID or PMG value that can be used. The MPAM driver has to
determine the system-wide minimum supported PARTID and PMG values.

To do this, the driver needs to be told what each requestor's limit is.

CPUs are special, but this infrastructure is also needed for the SMMU and
GIC ITS. Call the helper to tell the MPAM driver what the CPUs can do.

The return value can be ignored by the arch code as it runs well before the
MPAM driver starts probing.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 arch/arm64/kernel/mpam.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/arm64/kernel/mpam.c b/arch/arm64/kernel/mpam.c
index 9866d2ca0faa..e6feff2324ac 100644
--- a/arch/arm64/kernel/mpam.c
+++ b/arch/arm64/kernel/mpam.c
@@ -3,6 +3,7 @@
 
 #include <asm/mpam.h>
 
+#include <linux/arm_mpam.h>
 #include <linux/jump_label.h>
 #include <linux/percpu.h>
 
@@ -11,3 +12,14 @@ DEFINE_PER_CPU(u64, arm64_mpam_default);
 DEFINE_PER_CPU(u64, arm64_mpam_current);
 
 u64 arm64_mpam_global_default;
+
+static int __init arm64_mpam_register_cpus(void)
+{
+	u64 mpamidr = read_sanitised_ftr_reg(SYS_MPAMIDR_EL1);
+	u16 partid_max = FIELD_GET(MPAMIDR_EL1_PARTID_MAX, mpamidr);
+	u8 pmg_max = FIELD_GET(MPAMIDR_EL1_PMG_MAX, mpamidr);
+
+	return mpam_register_requestor(partid_max, pmg_max);
+}
+/* Must occur before mpam_msc_driver_init() from subsys_initcall() */
+arch_initcall(arm64_mpam_register_cpus)
-- 
2.43.0

Re: [PATCH v2 09/45] arm64: mpam: Advertise the CPUs MPAM limits to the driver

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:11 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> Requestors need to populate the MPAM fields for any traffic they send on
> the interconnect. For the CPUs these values are taken from the
> corresponding MPAMy_ELx register. Each requestor may have a limit on the
> largest PARTID or PMG value that can be used. The MPAM driver has to
> determine the system-wide minimum supported PARTID and PMG values.
> 
> To do this, the driver needs to be told what each requestor's limit is.
> 
> CPUs are special, but this infrastructure is also needed for the SMMU and
> GIC ITS. Call the helper to tell the MPAM driver what the CPUs can do.
> 
> The return value can be ignored by the arch code as it runs well before the
> MPAM driver starts probing.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

[PATCH v2 10/45] arm64: mpam: Add cpu_pm notifier to restore MPAM sysregs

[Ben Horgan]

From: James Morse <james.morse@arm.com>

The MPAM system registers will be lost if the CPU is reset during PSCI's
CPU_SUSPEND.

Add a PM notifier to restore them.

mpam_thread_switch(current) can't be used as this won't make any changes if
the in-memory copy says the register already has the correct value. In
reality the system register is UNKNOWN out of reset.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 arch/arm64/kernel/mpam.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/arch/arm64/kernel/mpam.c b/arch/arm64/kernel/mpam.c
index e6feff2324ac..dbe0a2d05abb 100644
--- a/arch/arm64/kernel/mpam.c
+++ b/arch/arm64/kernel/mpam.c
@@ -4,6 +4,7 @@
 #include <asm/mpam.h>
 
 #include <linux/arm_mpam.h>
+#include <linux/cpu_pm.h>
 #include <linux/jump_label.h>
 #include <linux/percpu.h>
 
@@ -13,12 +14,41 @@ DEFINE_PER_CPU(u64, arm64_mpam_current);
 
 u64 arm64_mpam_global_default;
 
+static int mpam_pm_notifier(struct notifier_block *self,
+			    unsigned long cmd, void *v)
+{
+	u64 regval;
+	int cpu = smp_processor_id();
+
+	switch (cmd) {
+	case CPU_PM_EXIT:
+		/*
+		 * Don't use mpam_thread_switch() as the system register
+		 * value has changed under our feet.
+		 */
+		regval = READ_ONCE(per_cpu(arm64_mpam_current, cpu));
+		write_sysreg_s(regval, SYS_MPAM1_EL1);
+		isb();
+
+		write_sysreg_s(regval, SYS_MPAM0_EL1);
+
+		return NOTIFY_OK;
+	default:
+		return NOTIFY_DONE;
+	}
+}
+
+static struct notifier_block mpam_pm_nb = {
+	.notifier_call = mpam_pm_notifier,
+};
+
 static int __init arm64_mpam_register_cpus(void)
 {
 	u64 mpamidr = read_sanitised_ftr_reg(SYS_MPAMIDR_EL1);
 	u16 partid_max = FIELD_GET(MPAMIDR_EL1_PARTID_MAX, mpamidr);
 	u8 pmg_max = FIELD_GET(MPAMIDR_EL1_PMG_MAX, mpamidr);
 
+	cpu_pm_register_notifier(&mpam_pm_nb);
 	return mpam_register_requestor(partid_max, pmg_max);
 }
 /* Must occur before mpam_msc_driver_init() from subsys_initcall() */
-- 
2.43.0

Re: [PATCH v2 10/45] arm64: mpam: Add cpu_pm notifier to restore MPAM sysregs

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:12 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> The MPAM system registers will be lost if the CPU is reset during PSCI's
> CPU_SUSPEND.
> 
> Add a PM notifier to restore them.
> 
> mpam_thread_switch(current) can't be used as this won't make any changes if
> the in-memory copy says the register already has the correct value. In
> reality the system register is UNKNOWN out of reset.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

[PATCH v2 11/45] arm64: mpam: Initialise and context switch the MPAMSM_EL1 register

[Ben Horgan]

The MPAMSM_EL1 sets the MPAM labels, PMG and PARTID, for loads and stores
generated by a shared SMCU. Disable the traps so the kernel can use it and
set it to the same configuration as the per-EL cpu MPAM configuration.

If an SMCU is not shared with other cpus then it is implementation defined
whether the configuration from MPAMSM_EL1 is used or that from the
appropriate MPAMy_ELx. As we set the same configuration for MPAM0_EL1,
MPAM1_EL1 and MPAMSM_EL1 the resulting configuration is the same
regardless.

Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 arch/arm64/include/asm/el2_setup.h | 3 ++-
 arch/arm64/include/asm/mpam.h      | 2 ++
 arch/arm64/kernel/cpufeature.c     | 2 ++
 arch/arm64/kernel/mpam.c           | 3 +++
 4 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
index cacd20df1786..d37984c09799 100644
--- a/arch/arm64/include/asm/el2_setup.h
+++ b/arch/arm64/include/asm/el2_setup.h
@@ -504,7 +504,8 @@
 	check_override id_aa64pfr0, ID_AA64PFR0_EL1_MPAM_SHIFT, .Linit_mpam_\@, .Lskip_mpam_\@, x1, x2
 
 .Linit_mpam_\@:
-	msr_s	SYS_MPAM2_EL2, xzr		// use the default partition
+	mov	x0, #MPAM2_EL2_EnMPAMSM_MASK
+	msr_s	SYS_MPAM2_EL2, x0		// use the default partition,
 						// and disable lower traps
 	mrs_s	x0, SYS_MPAMIDR_EL1
 	tbz	x0, #MPAMIDR_EL1_HAS_HCR_SHIFT, .Lskip_mpam_\@  // skip if no MPAMHCR reg
diff --git a/arch/arm64/include/asm/mpam.h b/arch/arm64/include/asm/mpam.h
index 2ab3dca6977c..c4cb015e8d8f 100644
--- a/arch/arm64/include/asm/mpam.h
+++ b/arch/arm64/include/asm/mpam.h
@@ -63,6 +63,8 @@ static inline void mpam_thread_switch(struct task_struct *tsk)
 		return;
 
 	write_sysreg_s(regval, SYS_MPAM1_EL1);
+	if (system_supports_sme())
+		write_sysreg_s(regval & (MPAMSM_EL1_PARTID_D | MPAMSM_EL1_PMG_D), SYS_MPAMSM_EL1);
 	isb();
 
 	/* Synchronising the EL0 write is left until the ERET to EL0 */
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 0cdfb3728f43..2ede543b3eeb 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2491,6 +2491,8 @@ cpu_enable_mpam(const struct arm64_cpu_capabilities *entry)
 		regval = READ_ONCE(per_cpu(arm64_mpam_current, cpu));
 
 	write_sysreg_s(regval, SYS_MPAM1_EL1);
+	if (system_supports_sme())
+		write_sysreg_s(regval & (MPAMSM_EL1_PARTID_D | MPAMSM_EL1_PMG_D), SYS_MPAMSM_EL1);
 	isb();
 
 	/* Synchronising the EL0 write is left until the ERET to EL0 */
diff --git a/arch/arm64/kernel/mpam.c b/arch/arm64/kernel/mpam.c
index dbe0a2d05abb..6ce4a36469ce 100644
--- a/arch/arm64/kernel/mpam.c
+++ b/arch/arm64/kernel/mpam.c
@@ -28,6 +28,9 @@ static int mpam_pm_notifier(struct notifier_block *self,
 		 */
 		regval = READ_ONCE(per_cpu(arm64_mpam_current, cpu));
 		write_sysreg_s(regval, SYS_MPAM1_EL1);
+		if (system_supports_sme())
+			write_sysreg_s(regval & (MPAMSM_EL1_PARTID_D | MPAMSM_EL1_PMG_D),
+				       SYS_MPAMSM_EL1);
 		isb();
 
 		write_sysreg_s(regval, SYS_MPAM0_EL1);
-- 
2.43.0

Re: [PATCH v2 11/45] arm64: mpam: Initialise and context switch the MPAMSM_EL1 register

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:13 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> The MPAMSM_EL1 sets the MPAM labels, PMG and PARTID, for loads and stores
> generated by a shared SMCU. Disable the traps so the kernel can use it and
> set it to the same configuration as the per-EL cpu MPAM configuration.
> 
> If an SMCU is not shared with other cpus then it is implementation defined
> whether the configuration from MPAMSM_EL1 is used or that from the
> appropriate MPAMy_ELx. As we set the same configuration for MPAM0_EL1,
> MPAM1_EL1 and MPAMSM_EL1 the resulting configuration is the same
> regardless.
Maybe tighten that last sentence up to talk about the matching fields
rather than the 'same configuration'.

Whole bunch of stuff in the first two that aren't in MPAMSM_EL1.
> 
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
LGTM
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

[PATCH v2 12/45] arm64: mpam: Add helpers to change a task or cpu's MPAM PARTID/PMG values

[Ben Horgan]

From: James Morse <james.morse@arm.com>

Care must be taken when modifying the PARTID and PMG of a task in any
per-task structure as writing these values may race with the task being
scheduled in, and reading the modified values.

Add helpers to set the task properties, and the CPU default value.  These
use WRITE_ONCE() that pairs with the READ_ONCE() in mpam_get_regval() to
avoid causing torn values.

CC: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Changes since rfc:
Keep comment attached to mpam_get_regval()
Add internal helper, __mpam_regval() (Jonathan)
---
 arch/arm64/include/asm/mpam.h | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/arch/arm64/include/asm/mpam.h b/arch/arm64/include/asm/mpam.h
index c4cb015e8d8f..a7fd0656bf90 100644
--- a/arch/arm64/include/asm/mpam.h
+++ b/arch/arm64/include/asm/mpam.h
@@ -4,6 +4,7 @@
 #ifndef __ASM__MPAM_H
 #define __ASM__MPAM_H
 
+#include <linux/bitfield.h>
 #include <linux/jump_label.h>
 #include <linux/percpu.h>
 #include <linux/sched.h>
@@ -22,6 +23,22 @@ DECLARE_PER_CPU(u64, arm64_mpam_current);
  */
 extern u64 arm64_mpam_global_default;
 
+static inline u64 __mpam_regval(u16 partid_d, u16 partid_i, u8 pmg_d, u8 pmg_i)
+{
+	return FIELD_PREP(MPAM0_EL1_PARTID_D, partid_d) |
+		FIELD_PREP(MPAM0_EL1_PARTID_I, partid_i) |
+		FIELD_PREP(MPAM0_EL1_PMG_D, pmg_d) |
+		FIELD_PREP(MPAM0_EL1_PMG_I, pmg_i);
+}
+
+static inline void mpam_set_cpu_defaults(int cpu, u16 partid_d, u16 partid_i,
+					 u8 pmg_d, u8 pmg_i)
+{
+	u64 default_val = __mpam_regval(partid_d, partid_i, pmg_d, pmg_i);
+
+	WRITE_ONCE(per_cpu(arm64_mpam_default, cpu), default_val);
+}
+
 /*
  * The resctrl filesystem writes to the partid/pmg values for threads and CPUs,
  * which may race with reads in mpam_thread_switch(). Ensure only one of the old
@@ -45,6 +62,17 @@ static inline u64 mpam_get_regval(struct task_struct *tsk)
 #endif
 }
 
+static inline void mpam_set_task_partid_pmg(struct task_struct *tsk,
+					    u16 partid_d, u16 partid_i,
+					    u8 pmg_d, u8 pmg_i)
+{
+#ifdef CONFIG_ARM64_MPAM
+	u64 regval = __mpam_regval(partid_d, partid_i, pmg_d, pmg_i);
+
+	WRITE_ONCE(task_thread_info(tsk)->mpam_partid_pmg, regval);
+#endif
+}
+
 static inline void mpam_thread_switch(struct task_struct *tsk)
 {
 	u64 oldregval;
-- 
2.43.0

Re: [PATCH v2 12/45] arm64: mpam: Add helpers to change a task or cpu's MPAM PARTID/PMG values

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:14 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> Care must be taken when modifying the PARTID and PMG of a task in any
> per-task structure as writing these values may race with the task being
> scheduled in, and reading the modified values.
> 
> Add helpers to set the task properties, and the CPU default value.  These
> use WRITE_ONCE() that pairs with the READ_ONCE() in mpam_get_regval() to
> avoid causing torn values.
> 
> CC: Dave Martin <Dave.Martin@arm.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

[PATCH v2 13/45] KVM: arm64: Force guest EL1 to use user-space's partid configuration

[Ben Horgan]

From: James Morse <james.morse@arm.com>

While we trap the guest's attempts to read/write the MPAM control
registers, the hardware continues to use them. Guest-EL0 uses KVM's
user-space's configuration, as the value is left in the register, and
guest-EL1 uses either the host kernel's configuration, or in the case of
VHE, the UNKNOWN reset value of MPAM1_EL1.

We want to force the guest-EL1 to use KVM's user-space's MPAM
configuration. On nVHE rely on MPAM0_EL1 and MPAM1_EL1 always being
programmed the same and on VHE copy MPAM0_EL1 into the guest's
MPAM1_EL1. There is no need to restore as this is out of context once TGE
is set.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Changes since rfc:
Drop the unneeded __mpam_guest_load() in nvhre and the MPAM1_EL1 save restore
Defer EL2 handling until next patch
---
 arch/arm64/kvm/hyp/vhe/sysreg-sr.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/arm64/kvm/hyp/vhe/sysreg-sr.c b/arch/arm64/kvm/hyp/vhe/sysreg-sr.c
index f28c6cf4fe1b..a2e8f6187675 100644
--- a/arch/arm64/kvm/hyp/vhe/sysreg-sr.c
+++ b/arch/arm64/kvm/hyp/vhe/sysreg-sr.c
@@ -183,6 +183,16 @@ void sysreg_restore_guest_state_vhe(struct kvm_cpu_context *ctxt)
 }
 NOKPROBE_SYMBOL(sysreg_restore_guest_state_vhe);
 
+/*
+ * The _EL0 value was written by the host's context switch and belongs to the
+ * VMM. Copy this into the guest's _EL1 register.
+ */
+static inline void __mpam_guest_load(void)
+{
+	if (system_supports_mpam())
+		write_sysreg_el1(read_sysreg_s(SYS_MPAM0_EL1), SYS_MPAM1);
+}
+
 /**
  * __vcpu_load_switch_sysregs - Load guest system registers to the physical CPU
  *
@@ -222,6 +232,7 @@ void __vcpu_load_switch_sysregs(struct kvm_vcpu *vcpu)
 	 */
 	__sysreg32_restore_state(vcpu);
 	__sysreg_restore_user_state(guest_ctxt);
+	__mpam_guest_load();
 
 	if (unlikely(is_hyp_ctxt(vcpu))) {
 		__sysreg_restore_vel2_state(vcpu);
-- 
2.43.0

Re: [PATCH v2 13/45] KVM: arm64: Force guest EL1 to use user-space's partid configuration

[Oliver Upton]

On Fri, Dec 19, 2025 at 06:11:15PM +0000, Ben Horgan wrote:
> From: James Morse <james.morse@arm.com>
> 
> While we trap the guest's attempts to read/write the MPAM control
> registers, the hardware continues to use them. Guest-EL0 uses KVM's
> user-space's configuration, as the value is left in the register, and
> guest-EL1 uses either the host kernel's configuration, or in the case of
> VHE, the UNKNOWN reset value of MPAM1_EL1.
> 
> We want to force the guest-EL1 to use KVM's user-space's MPAM
> configuration. On nVHE rely on MPAM0_EL1 and MPAM1_EL1 always being
> programmed the same and on VHE copy MPAM0_EL1 into the guest's
> MPAM1_EL1. There is no need to restore as this is out of context once TGE
> is set.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> ---
> Changes since rfc:
> Drop the unneeded __mpam_guest_load() in nvhre and the MPAM1_EL1 save restore
> Defer EL2 handling until next patch
> ---
>  arch/arm64/kvm/hyp/vhe/sysreg-sr.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/arch/arm64/kvm/hyp/vhe/sysreg-sr.c b/arch/arm64/kvm/hyp/vhe/sysreg-sr.c
> index f28c6cf4fe1b..a2e8f6187675 100644
> --- a/arch/arm64/kvm/hyp/vhe/sysreg-sr.c
> +++ b/arch/arm64/kvm/hyp/vhe/sysreg-sr.c
> @@ -183,6 +183,16 @@ void sysreg_restore_guest_state_vhe(struct kvm_cpu_context *ctxt)
>  }
>  NOKPROBE_SYMBOL(sysreg_restore_guest_state_vhe);
>  
> +/*
> + * The _EL0 value was written by the host's context switch and belongs to the
> + * VMM. Copy this into the guest's _EL1 register.
> + */
> +static inline void __mpam_guest_load(void)
> +{
> +	if (system_supports_mpam())
> +		write_sysreg_el1(read_sysreg_s(SYS_MPAM0_EL1), SYS_MPAM1);

nit: I'd prefer using a mask to extract the fields of interest, guarding
against future architecture doing something silly with the RES0 fields
of these registers.

Thanks,
Oliver

Re: [PATCH v2 13/45] KVM: arm64: Force guest EL1 to use user-space's partid configuration

[Ben Horgan]

Hi Oliver,

On 12/19/25 20:10, Oliver Upton wrote:
> On Fri, Dec 19, 2025 at 06:11:15PM +0000, Ben Horgan wrote:
>> From: James Morse <james.morse@arm.com>
>>
>> While we trap the guest's attempts to read/write the MPAM control
>> registers, the hardware continues to use them. Guest-EL0 uses KVM's
>> user-space's configuration, as the value is left in the register, and
>> guest-EL1 uses either the host kernel's configuration, or in the case of
>> VHE, the UNKNOWN reset value of MPAM1_EL1.
>>
>> We want to force the guest-EL1 to use KVM's user-space's MPAM
>> configuration. On nVHE rely on MPAM0_EL1 and MPAM1_EL1 always being
>> programmed the same and on VHE copy MPAM0_EL1 into the guest's
>> MPAM1_EL1. There is no need to restore as this is out of context once TGE
>> is set.
>>
>> Signed-off-by: James Morse <james.morse@arm.com>
>> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
>> ---
>> Changes since rfc:
>> Drop the unneeded __mpam_guest_load() in nvhre and the MPAM1_EL1 save restore
>> Defer EL2 handling until next patch
>> ---
>>  arch/arm64/kvm/hyp/vhe/sysreg-sr.c | 11 +++++++++++
>>  1 file changed, 11 insertions(+)
>>
>> diff --git a/arch/arm64/kvm/hyp/vhe/sysreg-sr.c b/arch/arm64/kvm/hyp/vhe/sysreg-sr.c
>> index f28c6cf4fe1b..a2e8f6187675 100644
>> --- a/arch/arm64/kvm/hyp/vhe/sysreg-sr.c
>> +++ b/arch/arm64/kvm/hyp/vhe/sysreg-sr.c
>> @@ -183,6 +183,16 @@ void sysreg_restore_guest_state_vhe(struct kvm_cpu_context *ctxt)
>>  }
>>  NOKPROBE_SYMBOL(sysreg_restore_guest_state_vhe);
>>  
>> +/*
>> + * The _EL0 value was written by the host's context switch and belongs to the
>> + * VMM. Copy this into the guest's _EL1 register.
>> + */
>> +static inline void __mpam_guest_load(void)
>> +{
>> +	if (system_supports_mpam())
>> +		write_sysreg_el1(read_sysreg_s(SYS_MPAM0_EL1), SYS_MPAM1);
> 
> nit: I'd prefer using a mask to extract the fields of interest, guarding
> against future architecture doing something silly with the RES0 fields
> of these registers.

Sure, I'll make this change.

> 
> Thanks,
> Oliver

Thanks,

Ben

[PATCH v2 14/45] KVM: arm64: Use kernel-space partid configuration for hypercalls

[Ben Horgan]

On nVHE systems whether or not MPAM is enabled, EL2 continues to use
partid-0 for hypercalls, even when the host may have configured its kernel
threads to use a different partid. 0 may have been assigned to another
task. Copy the EL1 MPAM register to EL2. This ensures hypercalls use the
same partid as the kernel thread does on the host.

Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 arch/arm64/kvm/hyp/nvhe/hyp-main.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index a7c689152f68..5c1de7e7dd38 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -635,6 +635,11 @@ static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)
 	unsigned long hcall_min = 0;
 	hcall_t hfn;
 
+	if (system_supports_mpam()) {
+		write_sysreg_s(read_sysreg_s(SYS_MPAM1_EL1), SYS_MPAM2_EL2);
+		isb();
+	}
+
 	/*
 	 * If pKVM has been initialised then reject any calls to the
 	 * early "privileged" hypercalls. Note that we cannot reject
-- 
2.43.0

[PATCH v2 15/45] arm_mpam: resctrl: Add boilerplate cpuhp and domain allocation

[Ben Horgan]

From: James Morse <james.morse@arm.com>

resctrl has its own data structures to describe its resources. We can't use
these directly as we play tricks with the 'MBA' resource, picking the MPAM
controls or monitors that best apply. We may export the same component as
both L3 and MBA.

Add mpam_resctrl_exports[] as the array of class->resctrl mappings we are
exporting, and add the cpuhp hooks that allocated and free the resctrl
domain structures.

While we're here, plumb in a few other obvious things.

CONFIG_ARM_CPU_RESCTRL is used to allow this code to be built even though
it can't yet be linked against resctrl.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Domain list is an rcu list
Add synchronize_rcu() to free the deleted element
Code flow simplification (Jonathan)
---
 drivers/resctrl/Makefile        |   1 +
 drivers/resctrl/mpam_devices.c  |  12 ++
 drivers/resctrl/mpam_internal.h |  22 +++
 drivers/resctrl/mpam_resctrl.c  | 329 ++++++++++++++++++++++++++++++++
 include/linux/arm_mpam.h        |   3 +
 5 files changed, 367 insertions(+)
 create mode 100644 drivers/resctrl/mpam_resctrl.c

diff --git a/drivers/resctrl/Makefile b/drivers/resctrl/Makefile
index 898199dcf80d..40beaf999582 100644
--- a/drivers/resctrl/Makefile
+++ b/drivers/resctrl/Makefile
@@ -1,4 +1,5 @@
 obj-$(CONFIG_ARM64_MPAM_DRIVER)			+= mpam.o
 mpam-y						+= mpam_devices.o
+mpam-$(CONFIG_ARM_CPU_RESCTRL)			+= mpam_resctrl.o
 
 ccflags-$(CONFIG_ARM64_MPAM_DRIVER_DEBUG)	+= -DDEBUG
diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 860181266b15..303aacfcb9d6 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -1628,6 +1628,9 @@ static int mpam_cpu_online(unsigned int cpu)
 			mpam_reprogram_msc(msc);
 	}
 
+	if (mpam_is_enabled())
+		mpam_resctrl_online_cpu(cpu);
+
 	return 0;
 }
 
@@ -1671,6 +1674,9 @@ static int mpam_cpu_offline(unsigned int cpu)
 {
 	struct mpam_msc *msc;
 
+	if (mpam_is_enabled())
+		mpam_resctrl_offline_cpu(cpu);
+
 	guard(srcu)(&mpam_srcu);
 	list_for_each_entry_srcu(msc, &mpam_all_msc, all_msc_list,
 				 srcu_read_lock_held(&mpam_srcu)) {
@@ -2517,6 +2523,12 @@ static void mpam_enable_once(void)
 	mutex_unlock(&mpam_list_lock);
 	cpus_read_unlock();
 
+	if (!err) {
+		err = mpam_resctrl_setup();
+		if (err)
+			pr_err("Failed to initialise resctrl: %d\n", err);
+	}
+
 	if (err) {
 		mpam_disable_reason = "Failed to enable.";
 		schedule_work(&mpam_broken_work);
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index e6e7ba4342d6..554e4887ba81 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -12,6 +12,7 @@
 #include <linux/jump_label.h>
 #include <linux/llist.h>
 #include <linux/mutex.h>
+#include <linux/resctrl.h>
 #include <linux/spinlock.h>
 #include <linux/srcu.h>
 #include <linux/types.h>
@@ -333,6 +334,17 @@ struct mpam_msc_ris {
 	struct mpam_garbage	garbage;
 };
 
+struct mpam_resctrl_dom {
+	struct mpam_component	*ctrl_comp;
+	struct rdt_ctrl_domain	resctrl_ctrl_dom;
+	struct rdt_mon_domain	resctrl_mon_dom;
+};
+
+struct mpam_resctrl_res {
+	struct mpam_class	*class;
+	struct rdt_resource	resctrl_res;
+};
+
 static inline int mpam_alloc_csu_mon(struct mpam_class *class)
 {
 	struct mpam_props *cprops = &class->props;
@@ -387,6 +399,16 @@ void mpam_msmon_reset_mbwu(struct mpam_component *comp, struct mon_cfg *ctx);
 int mpam_get_cpumask_from_cache_id(unsigned long cache_id, u32 cache_level,
 				   cpumask_t *affinity);
 
+#ifdef CONFIG_RESCTRL_FS
+int mpam_resctrl_setup(void);
+int mpam_resctrl_online_cpu(unsigned int cpu);
+void mpam_resctrl_offline_cpu(unsigned int cpu);
+#else
+static inline int mpam_resctrl_setup(void) { return 0; }
+static inline int mpam_resctrl_online_cpu(unsigned int cpu) { return 0; }
+static inline void mpam_resctrl_offline_cpu(unsigned int cpu) { }
+#endif /* CONFIG_RESCTRL_FS */
+
 /*
  * MPAM MSCs have the following register layout. See:
  * Arm Memory System Resource Partitioning and Monitoring (MPAM) System
diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
new file mode 100644
index 000000000000..4beeeded00ff
--- /dev/null
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -0,0 +1,329 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2025 Arm Ltd.
+
+#define pr_fmt(fmt) "%s:%s: " fmt, KBUILD_MODNAME, __func__
+
+#include <linux/arm_mpam.h>
+#include <linux/cacheinfo.h>
+#include <linux/cpu.h>
+#include <linux/cpumask.h>
+#include <linux/errno.h>
+#include <linux/list.h>
+#include <linux/printk.h>
+#include <linux/rculist.h>
+#include <linux/resctrl.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#include <asm/mpam.h>
+
+#include "mpam_internal.h"
+
+/*
+ * The classes we've picked to map to resctrl resources, wrapped
+ * in with their resctrl structure.
+ * Class pointer may be NULL.
+ */
+static struct mpam_resctrl_res mpam_resctrl_controls[RDT_NUM_RESOURCES];
+
+/* The lock for modifying resctrl's domain lists from cpuhp callbacks. */
+static DEFINE_MUTEX(domain_list_lock);
+
+static bool exposed_alloc_capable;
+static bool exposed_mon_capable;
+
+bool resctrl_arch_alloc_capable(void)
+{
+	return exposed_alloc_capable;
+}
+
+bool resctrl_arch_mon_capable(void)
+{
+	return exposed_mon_capable;
+}
+
+/*
+ * MSC may raise an error interrupt if it sees an out or range partid/pmg,
+ * and go on to truncate the value. Regardless of what the hardware supports,
+ * only the system wide safe value is safe to use.
+ */
+u32 resctrl_arch_get_num_closid(struct rdt_resource *ignored)
+{
+	return mpam_partid_max + 1;
+}
+
+struct rdt_resource *resctrl_arch_get_resource(enum resctrl_res_level l)
+{
+	if (l >= RDT_NUM_RESOURCES)
+		return NULL;
+
+	return &mpam_resctrl_controls[l].resctrl_res;
+}
+
+static int mpam_resctrl_control_init(struct mpam_resctrl_res *res,
+				     enum resctrl_res_level type)
+{
+	/* TODO: initialise the resctrl resources */
+
+	return 0;
+}
+
+static int mpam_resctrl_pick_domain_id(int cpu, struct mpam_component *comp)
+{
+	struct mpam_class *class = comp->class;
+
+	if (class->type == MPAM_CLASS_CACHE)
+		return comp->comp_id;
+
+	/* TODO: repaint domain ids to match the L3 domain ids */
+	/*
+	 * Otherwise, expose the ID used by the firmware table code.
+	 */
+	return comp->comp_id;
+}
+
+static void mpam_resctrl_domain_hdr_init(int cpu, struct mpam_component *comp,
+					 struct rdt_domain_hdr *hdr)
+{
+	lockdep_assert_cpus_held();
+
+	INIT_LIST_HEAD(&hdr->list);
+	hdr->id = mpam_resctrl_pick_domain_id(cpu, comp);
+	cpumask_set_cpu(cpu, &hdr->cpu_mask);
+}
+
+/**
+ * mpam_resctrl_offline_domain_hdr() - Update the domain header to remove a CPU.
+ * @cpu:	The CPU to remove from the domain.
+ * @hdr:	The domain's header.
+ *
+ * Removes @cpu from the header mask. If this was the last CPU in the domain,
+ * the domain header is removed from its parent list and true is returned,
+ * indicating the parent structure can be freed.
+ * If there are other CPUs in the domain, returns false.
+ */
+static bool mpam_resctrl_offline_domain_hdr(unsigned int cpu,
+					    struct rdt_domain_hdr *hdr)
+{
+	lockdep_assert_held(&domain_list_lock);
+
+	cpumask_clear_cpu(cpu, &hdr->cpu_mask);
+	if (cpumask_empty(&hdr->cpu_mask)) {
+		list_del_rcu(&hdr->list);
+		synchronize_rcu();
+		return true;
+	}
+
+	return false;
+}
+
+static struct mpam_resctrl_dom *
+mpam_resctrl_alloc_domain(unsigned int cpu, struct mpam_resctrl_res *res)
+{
+	int err;
+	struct mpam_resctrl_dom *dom;
+	struct rdt_mon_domain *mon_d;
+	struct rdt_ctrl_domain *ctrl_d;
+	struct mpam_class *class = res->class;
+	struct mpam_component *comp_iter, *ctrl_comp;
+	struct rdt_resource *r = &res->resctrl_res;
+
+	lockdep_assert_held(&domain_list_lock);
+
+	ctrl_comp = NULL;
+	guard(srcu)(&mpam_srcu);
+	list_for_each_entry_srcu(comp_iter, &class->components, class_list,
+				 srcu_read_lock_held(&mpam_srcu)) {
+		if (cpumask_test_cpu(cpu, &comp_iter->affinity)) {
+			ctrl_comp = comp_iter;
+			break;
+		}
+	}
+
+	/* class has no component for this CPU */
+	if (WARN_ON_ONCE(!ctrl_comp))
+		return ERR_PTR(-EINVAL);
+
+	dom = kzalloc_node(sizeof(*dom), GFP_KERNEL, cpu_to_node(cpu));
+	if (!dom)
+		return ERR_PTR(-ENOMEM);
+
+	if (exposed_alloc_capable) {
+		dom->ctrl_comp = ctrl_comp;
+
+		ctrl_d = &dom->resctrl_ctrl_dom;
+		mpam_resctrl_domain_hdr_init(cpu, ctrl_comp, &ctrl_d->hdr);
+		ctrl_d->hdr.type = RESCTRL_CTRL_DOMAIN;
+		/* TODO: this list should be sorted */
+		list_add_tail_rcu(&ctrl_d->hdr.list, &r->ctrl_domains);
+		err = resctrl_online_ctrl_domain(r, ctrl_d);
+		if (err) {
+			dom = ERR_PTR(err);
+			goto offline_ctrl_domain;
+		}
+	} else {
+		pr_debug("Skipped control domain online - no controls\n");
+	}
+
+	if (exposed_mon_capable) {
+		mon_d = &dom->resctrl_mon_dom;
+		mpam_resctrl_domain_hdr_init(cpu, ctrl_comp, &mon_d->hdr);
+		mon_d->hdr.type = RESCTRL_MON_DOMAIN;
+		/* TODO: this list should be sorted */
+		list_add_tail_rcu(&mon_d->hdr.list, &r->mon_domains);
+		err = resctrl_online_mon_domain(r, mon_d);
+		if (err) {
+			dom = ERR_PTR(err);
+			goto offline_mon_hdr;
+		}
+	} else {
+		pr_debug("Skipped monitor domain online - no monitors\n");
+	}
+
+	return dom;
+
+offline_mon_hdr:
+	mpam_resctrl_offline_domain_hdr(cpu, &mon_d->hdr);
+offline_ctrl_domain:
+	resctrl_offline_ctrl_domain(r, ctrl_d);
+
+	return dom;
+}
+
+static struct mpam_resctrl_dom *
+mpam_resctrl_get_domain_from_cpu(int cpu, struct mpam_resctrl_res *res)
+{
+	struct mpam_resctrl_dom *dom;
+	struct rdt_ctrl_domain *ctrl_d;
+	struct rdt_resource *r = &res->resctrl_res;
+
+	lockdep_assert_cpus_held();
+
+	list_for_each_entry_rcu(ctrl_d, &r->ctrl_domains, hdr.list) {
+		dom = container_of(ctrl_d, struct mpam_resctrl_dom,
+				   resctrl_ctrl_dom);
+
+		if (cpumask_test_cpu(cpu, &dom->ctrl_comp->affinity))
+			return dom;
+	}
+
+	return NULL;
+}
+
+int mpam_resctrl_online_cpu(unsigned int cpu)
+{
+	guard(mutex)(&domain_list_lock);
+	for (int i = 0; i < RDT_NUM_RESOURCES; i++) {
+		struct mpam_resctrl_dom *dom;
+		struct mpam_resctrl_res *res;
+
+		res = &mpam_resctrl_controls[i];
+		if (!res->class)
+			continue;	// dummy_resource;
+
+		dom = mpam_resctrl_get_domain_from_cpu(cpu, res);
+		if (!dom)
+			dom = mpam_resctrl_alloc_domain(cpu, res);
+		if (IS_ERR(dom))
+			return PTR_ERR(dom);
+	}
+
+	resctrl_online_cpu(cpu);
+
+	return 0;
+}
+
+void mpam_resctrl_offline_cpu(unsigned int cpu)
+{
+	resctrl_offline_cpu(cpu);
+
+	guard(mutex)(&domain_list_lock);
+	for (int i = 0; i < RDT_NUM_RESOURCES; i++) {
+		struct mpam_resctrl_res *res;
+		struct mpam_resctrl_dom *dom;
+		struct rdt_mon_domain *mon_d;
+		struct rdt_ctrl_domain *ctrl_d;
+		bool ctrl_dom_empty, mon_dom_empty;
+
+		res = &mpam_resctrl_controls[i];
+		if (!res->class)
+			continue;	// dummy resource
+
+		dom = mpam_resctrl_get_domain_from_cpu(cpu, res);
+		if (WARN_ON_ONCE(!dom))
+			continue;
+
+		ctrl_dom_empty = true;
+		if (exposed_alloc_capable) {
+			ctrl_d = &dom->resctrl_ctrl_dom;
+			ctrl_dom_empty = mpam_resctrl_offline_domain_hdr(cpu, &ctrl_d->hdr);
+			if (ctrl_dom_empty)
+				resctrl_offline_ctrl_domain(&res->resctrl_res, ctrl_d);
+		}
+
+		mon_dom_empty = true;
+		if (exposed_mon_capable) {
+			mon_d = &dom->resctrl_mon_dom;
+			mon_dom_empty = mpam_resctrl_offline_domain_hdr(cpu, &mon_d->hdr);
+			if (mon_dom_empty)
+				resctrl_offline_mon_domain(&res->resctrl_res, mon_d);
+		}
+
+		if (ctrl_dom_empty && mon_dom_empty)
+			kfree(dom);
+	}
+}
+
+int mpam_resctrl_setup(void)
+{
+	int err = 0;
+	struct mpam_resctrl_res *res;
+
+	cpus_read_lock();
+	for (enum resctrl_res_level i = 0; i < RDT_NUM_RESOURCES; i++) {
+		res = &mpam_resctrl_controls[i];
+		INIT_LIST_HEAD_RCU(&res->resctrl_res.ctrl_domains);
+		INIT_LIST_HEAD_RCU(&res->resctrl_res.mon_domains);
+		res->resctrl_res.rid = i;
+	}
+
+	/* TODO: pick MPAM classes to map to resctrl resources */
+
+	/* Initialise the resctrl structures from the classes */
+	for (enum resctrl_res_level i = 0; i < RDT_NUM_RESOURCES; i++) {
+		res = &mpam_resctrl_controls[i];
+		if (!res->class)
+			continue;	// dummy resource
+
+		err = mpam_resctrl_control_init(res, i);
+		if (err) {
+			pr_debug("Failed to initialise rid %u\n", i);
+			break;
+		}
+	}
+	cpus_read_unlock();
+
+	if (err) {
+		pr_debug("Internal error %d - resctrl not supported\n", err);
+		return err;
+	}
+
+	if (!exposed_alloc_capable && !exposed_mon_capable) {
+		pr_debug("No alloc(%u) or monitor(%u) found - resctrl not supported\n",
+			 exposed_alloc_capable, exposed_mon_capable);
+		return -EOPNOTSUPP;
+	}
+
+	if (!is_power_of_2(mpam_pmg_max + 1)) {
+		/*
+		 * If not all the partid*pmg values are valid indexes,
+		 * resctrl may allocate pmg that don't exist. This
+		 * should cause an error interrupt.
+		 */
+		pr_warn("Number of PMG is not a power of 2! resctrl may misbehave");
+	}
+
+	/* TODO: call resctrl_init() */
+
+	return err;
+}
diff --git a/include/linux/arm_mpam.h b/include/linux/arm_mpam.h
index 7f00c5285a32..2c7d1413a401 100644
--- a/include/linux/arm_mpam.h
+++ b/include/linux/arm_mpam.h
@@ -49,6 +49,9 @@ static inline int mpam_ris_create(struct mpam_msc *msc, u8 ris_idx,
 }
 #endif
 
+bool resctrl_arch_alloc_capable(void);
+bool resctrl_arch_mon_capable(void);
+
 /**
  * mpam_register_requestor() - Register a requestor with the MPAM driver
  * @partid_max:		The maximum PARTID value the requestor can generate.
-- 
2.43.0

Re: [PATCH v2 15/45] arm_mpam: resctrl: Add boilerplate cpuhp and domain allocation

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:17 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> resctrl has its own data structures to describe its resources. We can't use
> these directly as we play tricks with the 'MBA' resource, picking the MPAM
> controls or monitors that best apply. We may export the same component as
> both L3 and MBA.
> 
> Add mpam_resctrl_exports[] as the array of class->resctrl mappings we are
> exporting, and add the cpuhp hooks that allocated and free the resctrl
> domain structures.
> 
> While we're here, plumb in a few other obvious things.
> 
> CONFIG_ARM_CPU_RESCTRL is used to allow this code to be built even though
> it can't yet be linked against resctrl.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> ---
> Domain list is an rcu list
> Add synchronize_rcu() to free the deleted element
> Code flow simplification (Jonathan)

Just trivial stuff and that one what do we loop over thing that
we continued discussing in the RFC thread (I think you already
tidied that up)  Nothing here to stop:
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
(which is another way of saying I'm not planning to read it again :)


> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> new file mode 100644
> index 000000000000..4beeeded00ff
> --- /dev/null
> +++ b/drivers/resctrl/mpam_resctrl.c

> +
> +static int mpam_resctrl_pick_domain_id(int cpu, struct mpam_component *comp)
> +{
> +	struct mpam_class *class = comp->class;
> +
> +	if (class->type == MPAM_CLASS_CACHE)
> +		return comp->comp_id;
> +
> +	/* TODO: repaint domain ids to match the L3 domain ids */
> +	/*
> +	 * Otherwise, expose the ID used by the firmware table code.
Maybe more turns up in here. Otherwise, easily fits in single line comment.
> +	 */
> +	return comp->comp_id;
> +}

> +static struct mpam_resctrl_dom *
> +mpam_resctrl_get_domain_from_cpu(int cpu, struct mpam_resctrl_res *res)
> +{
> +	struct mpam_resctrl_dom *dom;
> +	struct rdt_ctrl_domain *ctrl_d;
> +	struct rdt_resource *r = &res->resctrl_res;
> +
> +	lockdep_assert_cpus_held();
> +
> +	list_for_each_entry_rcu(ctrl_d, &r->ctrl_domains, hdr.list) {

As a reminder, though I think you already changed this, discussion carried
on wrt to the RFC version of this loop.

> +		dom = container_of(ctrl_d, struct mpam_resctrl_dom,
> +				   resctrl_ctrl_dom);
> +
> +		if (cpumask_test_cpu(cpu, &dom->ctrl_comp->affinity))
> +			return dom;
> +	}
> +
> +	return NULL;
> +}

> +
> +void mpam_resctrl_offline_cpu(unsigned int cpu)
> +{
> +	resctrl_offline_cpu(cpu);
> +
> +	guard(mutex)(&domain_list_lock);
> +	for (int i = 0; i < RDT_NUM_RESOURCES; i++) {
> +		struct mpam_resctrl_res *res;
> +		struct mpam_resctrl_dom *dom;
> +		struct rdt_mon_domain *mon_d;
> +		struct rdt_ctrl_domain *ctrl_d;
> +		bool ctrl_dom_empty, mon_dom_empty;
> +
> +		res = &mpam_resctrl_controls[i];
> +		if (!res->class)
> +			continue;	// dummy resource
> +
> +		dom = mpam_resctrl_get_domain_from_cpu(cpu, res);
> +		if (WARN_ON_ONCE(!dom))
> +			continue;
> +
> +		ctrl_dom_empty = true;
> +		if (exposed_alloc_capable) {
> +			ctrl_d = &dom->resctrl_ctrl_dom;
> +			ctrl_dom_empty = mpam_resctrl_offline_domain_hdr(cpu, &ctrl_d->hdr);
> +			if (ctrl_dom_empty)
> +				resctrl_offline_ctrl_domain(&res->resctrl_res, ctrl_d);
> +		}
really small thing but I'd do 
		} else {
			ctrl_dom_empty = true;
		}
here to make it visually obvious why that is set to true. The initialize and override
if we have more info pattern is to me less readable.

> +
> +		mon_dom_empty = true;
> +		if (exposed_mon_capable) {
> +			mon_d = &dom->resctrl_mon_dom;
> +			mon_dom_empty = mpam_resctrl_offline_domain_hdr(cpu, &mon_d->hdr);
> +			if (mon_dom_empty)
> +				resctrl_offline_mon_domain(&res->resctrl_res, mon_d);
> +		}
Similar for this one.
> +
> +		if (ctrl_dom_empty && mon_dom_empty)
> +			kfree(dom);
> +	}
> +}

Re: [PATCH v2 15/45] arm_mpam: resctrl: Add boilerplate cpuhp and domain allocation

[Ben Horgan]

Hi Jonathan,

On 1/5/26 17:40, Jonathan Cameron wrote:
> On Fri, 19 Dec 2025 18:11:17 +0000
> Ben Horgan <ben.horgan@arm.com> wrote:
> 
>> From: James Morse <james.morse@arm.com>
>>
>> resctrl has its own data structures to describe its resources. We can't use
>> these directly as we play tricks with the 'MBA' resource, picking the MPAM
>> controls or monitors that best apply. We may export the same component as
>> both L3 and MBA.
>>
>> Add mpam_resctrl_exports[] as the array of class->resctrl mappings we are
>> exporting, and add the cpuhp hooks that allocated and free the resctrl
>> domain structures.
>>
>> While we're here, plumb in a few other obvious things.
>>
>> CONFIG_ARM_CPU_RESCTRL is used to allow this code to be built even though
>> it can't yet be linked against resctrl.
>>
>> Signed-off-by: James Morse <james.morse@arm.com>
>> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
>> ---
>> Domain list is an rcu list
>> Add synchronize_rcu() to free the deleted element
>> Code flow simplification (Jonathan)
> 
> Just trivial stuff and that one what do we loop over thing that
> we continued discussing in the RFC thread (I think you already
> tidied that up)  Nothing here to stop:
> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
> (which is another way of saying I'm not planning to read it again :)

Yes, I've already made that change locally :) and just added your other
suggestions below.

> 
> 
>> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
>> new file mode 100644
>> index 000000000000..4beeeded00ff
>> --- /dev/null
>> +++ b/drivers/resctrl/mpam_resctrl.c
> 
>> +
>> +static int mpam_resctrl_pick_domain_id(int cpu, struct mpam_component *comp)
>> +{
>> +	struct mpam_class *class = comp->class;
>> +
>> +	if (class->type == MPAM_CLASS_CACHE)
>> +		return comp->comp_id;
>> +
>> +	/* TODO: repaint domain ids to match the L3 domain ids */
>> +	/*
>> +	 * Otherwise, expose the ID used by the firmware table code.
> Maybe more turns up in here. Otherwise, easily fits in single line comment.
>> +	 */
>> +	return comp->comp_id;
>> +}
> 
>> +static struct mpam_resctrl_dom *
>> +mpam_resctrl_get_domain_from_cpu(int cpu, struct mpam_resctrl_res *res)
>> +{
>> +	struct mpam_resctrl_dom *dom;
>> +	struct rdt_ctrl_domain *ctrl_d;
>> +	struct rdt_resource *r = &res->resctrl_res;
>> +
>> +	lockdep_assert_cpus_held();
>> +
>> +	list_for_each_entry_rcu(ctrl_d, &r->ctrl_domains, hdr.list) {
> 
> As a reminder, though I think you already changed this, discussion carried
> on wrt to the RFC version of this loop.
> 
>> +		dom = container_of(ctrl_d, struct mpam_resctrl_dom,
>> +				   resctrl_ctrl_dom);
>> +
>> +		if (cpumask_test_cpu(cpu, &dom->ctrl_comp->affinity))
>> +			return dom;
>> +	}
>> +
>> +	return NULL;
>> +}
> 
>> +
>> +void mpam_resctrl_offline_cpu(unsigned int cpu)
>> +{
>> +	resctrl_offline_cpu(cpu);
>> +
>> +	guard(mutex)(&domain_list_lock);
>> +	for (int i = 0; i < RDT_NUM_RESOURCES; i++) {
>> +		struct mpam_resctrl_res *res;
>> +		struct mpam_resctrl_dom *dom;
>> +		struct rdt_mon_domain *mon_d;
>> +		struct rdt_ctrl_domain *ctrl_d;
>> +		bool ctrl_dom_empty, mon_dom_empty;
>> +
>> +		res = &mpam_resctrl_controls[i];
>> +		if (!res->class)
>> +			continue;	// dummy resource
>> +
>> +		dom = mpam_resctrl_get_domain_from_cpu(cpu, res);
>> +		if (WARN_ON_ONCE(!dom))
>> +			continue;
>> +
>> +		ctrl_dom_empty = true;
>> +		if (exposed_alloc_capable) {
>> +			ctrl_d = &dom->resctrl_ctrl_dom;
>> +			ctrl_dom_empty = mpam_resctrl_offline_domain_hdr(cpu, &ctrl_d->hdr);
>> +			if (ctrl_dom_empty)
>> +				resctrl_offline_ctrl_domain(&res->resctrl_res, ctrl_d);
>> +		}
> really small thing but I'd do 
> 		} else {
> 			ctrl_dom_empty = true;
> 		}
> here to make it visually obvious why that is set to true. The initialize and override
> if we have more info pattern is to me less readable.
> 
>> +
>> +		mon_dom_empty = true;
>> +		if (exposed_mon_capable) {
>> +			mon_d = &dom->resctrl_mon_dom;
>> +			mon_dom_empty = mpam_resctrl_offline_domain_hdr(cpu, &mon_d->hdr);
>> +			if (mon_dom_empty)
>> +				resctrl_offline_mon_domain(&res->resctrl_res, mon_d);
>> +		}
> Similar for this one.
>> +
>> +		if (ctrl_dom_empty && mon_dom_empty)
>> +			kfree(dom);
>> +	}
>> +}
> 

-- 
Thanks,

Ben

[PATCH v2 16/45] arm_mpam: resctrl: Sort the order of the domain lists

[Ben Horgan]

From: James Morse <james.morse@arm.com>

resctrl documents that the domains appear in numeric order in the schemata
file. This means a little more work is needed when bringing a domain
online.

Add the support for this, using resctrl_find_domain() to find the point to
insert in the list.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 drivers/resctrl/mpam_resctrl.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 4beeeded00ff..5481d9cc69d9 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -117,6 +117,21 @@ static bool mpam_resctrl_offline_domain_hdr(unsigned int cpu,
 	return false;
 }
 
+static void mpam_resctrl_domain_insert(struct list_head *list,
+				       struct rdt_domain_hdr *new)
+{
+	struct rdt_domain_hdr *err;
+	struct list_head *pos = NULL;
+
+	lockdep_assert_held(&domain_list_lock);
+
+	err = resctrl_find_domain(list, new->id, &pos);
+	if (WARN_ON_ONCE(err))
+		return;
+
+	list_add_tail_rcu(&new->list, pos);
+}
+
 static struct mpam_resctrl_dom *
 mpam_resctrl_alloc_domain(unsigned int cpu, struct mpam_resctrl_res *res)
 {
@@ -154,8 +169,7 @@ mpam_resctrl_alloc_domain(unsigned int cpu, struct mpam_resctrl_res *res)
 		ctrl_d = &dom->resctrl_ctrl_dom;
 		mpam_resctrl_domain_hdr_init(cpu, ctrl_comp, &ctrl_d->hdr);
 		ctrl_d->hdr.type = RESCTRL_CTRL_DOMAIN;
-		/* TODO: this list should be sorted */
-		list_add_tail_rcu(&ctrl_d->hdr.list, &r->ctrl_domains);
+		mpam_resctrl_domain_insert(&r->ctrl_domains, &ctrl_d->hdr);
 		err = resctrl_online_ctrl_domain(r, ctrl_d);
 		if (err) {
 			dom = ERR_PTR(err);
@@ -169,8 +183,7 @@ mpam_resctrl_alloc_domain(unsigned int cpu, struct mpam_resctrl_res *res)
 		mon_d = &dom->resctrl_mon_dom;
 		mpam_resctrl_domain_hdr_init(cpu, ctrl_comp, &mon_d->hdr);
 		mon_d->hdr.type = RESCTRL_MON_DOMAIN;
-		/* TODO: this list should be sorted */
-		list_add_tail_rcu(&mon_d->hdr.list, &r->mon_domains);
+		mpam_resctrl_domain_insert(&r->mon_domains, &mon_d->hdr);
 		err = resctrl_online_mon_domain(r, mon_d);
 		if (err) {
 			dom = ERR_PTR(err);
-- 
2.43.0

Re: [PATCH v2 16/45] arm_mpam: resctrl: Sort the order of the domain lists

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:18 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> resctrl documents that the domains appear in numeric order in the schemata
> file. This means a little more work is needed when bringing a domain
> online.
> 
> Add the support for this, using resctrl_find_domain() to find the point to
> insert in the list.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
I guess this was split out to try and make previous patch easier to read.
I'm not sure I'd bother in this particular case as those TODOs were
ugly, but anyhow LGTM

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> ---
>  drivers/resctrl/mpam_resctrl.c | 21 +++++++++++++++++----
>  1 file changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> index 4beeeded00ff..5481d9cc69d9 100644
> --- a/drivers/resctrl/mpam_resctrl.c
> +++ b/drivers/resctrl/mpam_resctrl.c
> @@ -117,6 +117,21 @@ static bool mpam_resctrl_offline_domain_hdr(unsigned int cpu,
>  	return false;
>  }
>  
> +static void mpam_resctrl_domain_insert(struct list_head *list,
> +				       struct rdt_domain_hdr *new)
> +{
> +	struct rdt_domain_hdr *err;
> +	struct list_head *pos = NULL;
> +
> +	lockdep_assert_held(&domain_list_lock);
> +
> +	err = resctrl_find_domain(list, new->id, &pos);
> +	if (WARN_ON_ONCE(err))
> +		return;
> +
> +	list_add_tail_rcu(&new->list, pos);
> +}
> +
>  static struct mpam_resctrl_dom *
>  mpam_resctrl_alloc_domain(unsigned int cpu, struct mpam_resctrl_res *res)
>  {
> @@ -154,8 +169,7 @@ mpam_resctrl_alloc_domain(unsigned int cpu, struct mpam_resctrl_res *res)
>  		ctrl_d = &dom->resctrl_ctrl_dom;
>  		mpam_resctrl_domain_hdr_init(cpu, ctrl_comp, &ctrl_d->hdr);
>  		ctrl_d->hdr.type = RESCTRL_CTRL_DOMAIN;
> -		/* TODO: this list should be sorted */
> -		list_add_tail_rcu(&ctrl_d->hdr.list, &r->ctrl_domains);
> +		mpam_resctrl_domain_insert(&r->ctrl_domains, &ctrl_d->hdr);
>  		err = resctrl_online_ctrl_domain(r, ctrl_d);
>  		if (err) {
>  			dom = ERR_PTR(err);
> @@ -169,8 +183,7 @@ mpam_resctrl_alloc_domain(unsigned int cpu, struct mpam_resctrl_res *res)
>  		mon_d = &dom->resctrl_mon_dom;
>  		mpam_resctrl_domain_hdr_init(cpu, ctrl_comp, &mon_d->hdr);
>  		mon_d->hdr.type = RESCTRL_MON_DOMAIN;
> -		/* TODO: this list should be sorted */
> -		list_add_tail_rcu(&mon_d->hdr.list, &r->mon_domains);
> +		mpam_resctrl_domain_insert(&r->mon_domains, &mon_d->hdr);
>  		err = resctrl_online_mon_domain(r, mon_d);
>  		if (err) {
>  			dom = ERR_PTR(err);

[PATCH v2 17/45] arm_mpam: resctrl: Pick the caches we will use as resctrl resources

[Ben Horgan]

From: James Morse <james.morse@arm.com>

Systems with MPAM support may have a variety of control types at any point
of their system layout. We can only expose certain types of control, and
only if they exist at particular locations.

Start with the well-known caches. These have to be depth 2 or 3 and support
MPAM's cache portion bitmap controls, with a number of portions fewer than
resctrl's limit.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Changes since rfc:
Jonathan:
Remove brackets
Compress debug message
Use temp var, r
---
 drivers/resctrl/mpam_resctrl.c | 90 +++++++++++++++++++++++++++++++++-
 1 file changed, 88 insertions(+), 2 deletions(-)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 5481d9cc69d9..bc4f1c80eab5 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -60,10 +60,95 @@ struct rdt_resource *resctrl_arch_get_resource(enum resctrl_res_level l)
 	return &mpam_resctrl_controls[l].resctrl_res;
 }
 
+static bool cache_has_usable_cpor(struct mpam_class *class)
+{
+	struct mpam_props *cprops = &class->props;
+
+	if (!mpam_has_feature(mpam_feat_cpor_part, cprops))
+		return false;
+
+	/* resctrl uses u32 for all bitmap configurations */
+	return class->props.cpbm_wd <= 32;
+}
+
+/* Test whether we can export MPAM_CLASS_CACHE:{2,3}? */
+static void mpam_resctrl_pick_caches(void)
+{
+	struct mpam_class *class;
+	struct mpam_resctrl_res *res;
+
+	lockdep_assert_cpus_held();
+
+	guard(srcu)(&mpam_srcu);
+	list_for_each_entry_srcu(class, &mpam_classes, classes_list,
+				 srcu_read_lock_held(&mpam_srcu)) {
+		if (class->type != MPAM_CLASS_CACHE) {
+			pr_debug("class %u is not a cache\n", class->level);
+			continue;
+		}
+
+		if (class->level != 2 && class->level != 3) {
+			pr_debug("class %u is not L2 or L3\n", class->level);
+			continue;
+		}
+
+		if (!cache_has_usable_cpor(class)) {
+			pr_debug("class %u cache misses CPOR\n", class->level);
+			continue;
+		}
+
+		if (!cpumask_equal(&class->affinity, cpu_possible_mask)) {
+			pr_debug("class %u has missing CPUs, mask %*pb != %*pb\n", class->level,
+				 cpumask_pr_args(&class->affinity),
+				 cpumask_pr_args(cpu_possible_mask));
+			continue;
+		}
+
+		if (class->level == 2)
+			res = &mpam_resctrl_controls[RDT_RESOURCE_L2];
+		else
+			res = &mpam_resctrl_controls[RDT_RESOURCE_L3];
+		res->class = class;
+		exposed_alloc_capable = true;
+	}
+}
+
 static int mpam_resctrl_control_init(struct mpam_resctrl_res *res,
 				     enum resctrl_res_level type)
 {
-	/* TODO: initialise the resctrl resources */
+	struct mpam_class *class = res->class;
+	struct rdt_resource *r = &res->resctrl_res;
+
+	switch (r->rid) {
+	case RDT_RESOURCE_L2:
+	case RDT_RESOURCE_L3:
+		r->alloc_capable = true;
+		r->schema_fmt = RESCTRL_SCHEMA_BITMAP;
+		r->cache.arch_has_sparse_bitmasks = true;
+
+		r->cache.cbm_len = class->props.cpbm_wd;
+		/* mpam_devices will reject empty bitmaps */
+		r->cache.min_cbm_bits = 1;
+
+		if (r->rid == RDT_RESOURCE_L2) {
+			r->name = "L2";
+			r->ctrl_scope = RESCTRL_L2_CACHE;
+		} else {
+			r->name = "L3";
+			r->ctrl_scope = RESCTRL_L3_CACHE;
+		}
+
+		/*
+		 * Which bits are shared with other ...things...
+		 * Unknown devices use partid-0 which uses all the bitmap
+		 * fields. Until we configured the SMMU and GIC not to do this
+		 * 'all the bits' is the correct answer here.
+		 */
+		r->cache.shareable_bits = resctrl_get_default_ctrl(r);
+		break;
+	default:
+		break;
+	}
 
 	return 0;
 }
@@ -300,7 +385,8 @@ int mpam_resctrl_setup(void)
 		res->resctrl_res.rid = i;
 	}
 
-	/* TODO: pick MPAM classes to map to resctrl resources */
+	/* Find some classes to use for controls */
+	mpam_resctrl_pick_caches();
 
 	/* Initialise the resctrl structures from the classes */
 	for (enum resctrl_res_level i = 0; i < RDT_NUM_RESOURCES; i++) {
-- 
2.43.0

Re: [PATCH v2 17/45] arm_mpam: resctrl: Pick the caches we will use as resctrl resources

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:19 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> Systems with MPAM support may have a variety of control types at any point
> of their system layout. We can only expose certain types of control, and
> only if they exist at particular locations.
> 
> Start with the well-known caches. These have to be depth 2 or 3 and support
> MPAM's cache portion bitmap controls, with a number of portions fewer than
> resctrl's limit.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

Note that I'm far from familiar with all the details of the resctl side
of things so assuming that will be well covered by other reviewers!

Jonathan

> ---
> Changes since rfc:
> Jonathan:
> Remove brackets
> Compress debug message
> Use temp var, r
> ---
>  drivers/resctrl/mpam_resctrl.c | 90 +++++++++++++++++++++++++++++++++-
>  1 file changed, 88 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> index 5481d9cc69d9..bc4f1c80eab5 100644
> --- a/drivers/resctrl/mpam_resctrl.c
> +++ b/drivers/resctrl/mpam_resctrl.c
> @@ -60,10 +60,95 @@ struct rdt_resource *resctrl_arch_get_resource(enum resctrl_res_level l)
>  	return &mpam_resctrl_controls[l].resctrl_res;
>  }
>  
> +static bool cache_has_usable_cpor(struct mpam_class *class)
> +{
> +	struct mpam_props *cprops = &class->props;
> +
> +	if (!mpam_has_feature(mpam_feat_cpor_part, cprops))
> +		return false;
> +
> +	/* resctrl uses u32 for all bitmap configurations */
> +	return class->props.cpbm_wd <= 32;
> +}

[PATCH v2 18/45] arm_mpam: resctrl: Implement resctrl_arch_reset_all_ctrls()

[Ben Horgan]

From: James Morse <james.morse@arm.com>

We already have a helper for resetting an mpam class and component.  Hook
it up to resctrl_arch_reset_all_ctrls() and the domain offline path.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 drivers/resctrl/mpam_devices.c  |  6 +++---
 drivers/resctrl/mpam_internal.h |  7 +++++++
 drivers/resctrl/mpam_resctrl.c  | 15 +++++++++++++++
 3 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 303aacfcb9d6..4f5d908d02a9 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -2544,7 +2544,7 @@ static void mpam_enable_once(void)
 	       mpam_partid_max + 1, mpam_pmg_max + 1);
 }
 
-static void mpam_reset_component_locked(struct mpam_component *comp)
+void mpam_reset_component_locked(struct mpam_component *comp)
 {
 	struct mpam_vmsc *vmsc;
 
@@ -2568,7 +2568,7 @@ static void mpam_reset_component_locked(struct mpam_component *comp)
 	}
 }
 
-static void mpam_reset_class_locked(struct mpam_class *class)
+void mpam_reset_class_locked(struct mpam_class *class)
 {
 	struct mpam_component *comp;
 
@@ -2580,7 +2580,7 @@ static void mpam_reset_class_locked(struct mpam_class *class)
 		mpam_reset_component_locked(comp);
 }
 
-static void mpam_reset_class(struct mpam_class *class)
+void mpam_reset_class(struct mpam_class *class)
 {
 	cpus_read_lock();
 	mpam_reset_class_locked(class);
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index 554e4887ba81..b9a739abb101 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -389,6 +389,13 @@ extern u8 mpam_pmg_max;
 void mpam_enable(struct work_struct *work);
 void mpam_disable(struct work_struct *work);
 
+/* Reset all the RIS in a class, optionally while holding cpus_read_lock() */
+void mpam_reset_class_locked(struct mpam_class *class);
+void mpam_reset_class(struct mpam_class *class);
+
+/* Reset all the RIS in a component under cpus_read_lock() */
+void mpam_reset_component_locked(struct mpam_component *comp);
+
 int mpam_apply_config(struct mpam_component *comp, u16 partid,
 		      struct mpam_config *cfg);
 
diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index bc4f1c80eab5..d32e87002457 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -167,6 +167,19 @@ static int mpam_resctrl_pick_domain_id(int cpu, struct mpam_component *comp)
 	return comp->comp_id;
 }
 
+void resctrl_arch_reset_all_ctrls(struct rdt_resource *r)
+{
+	struct mpam_resctrl_res *res;
+
+	lockdep_assert_cpus_held();
+
+	if (!mpam_is_enabled())
+		return;
+
+	res = container_of(r, struct mpam_resctrl_res, resctrl_res);
+	mpam_reset_class_locked(res->class);
+}
+
 static void mpam_resctrl_domain_hdr_init(int cpu, struct mpam_component *comp,
 					 struct rdt_domain_hdr *hdr)
 {
@@ -353,6 +366,8 @@ void mpam_resctrl_offline_cpu(unsigned int cpu)
 
 		ctrl_dom_empty = true;
 		if (exposed_alloc_capable) {
+			mpam_reset_component_locked(dom->ctrl_comp);
+
 			ctrl_d = &dom->resctrl_ctrl_dom;
 			ctrl_dom_empty = mpam_resctrl_offline_domain_hdr(cpu, &ctrl_d->hdr);
 			if (ctrl_dom_empty)
-- 
2.43.0

Re: [PATCH v2 18/45] arm_mpam: resctrl: Implement resctrl_arch_reset_all_ctrls()

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:20 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> We already have a helper for resetting an mpam class and component.  Hook
> it up to resctrl_arch_reset_all_ctrls() and the domain offline path.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
I left all the context as my one comment on this is I don't see a reason
to expose mpam_reset_class()  Only the _locked() variant ever seems to be
used outside of mpam_devices.c

> ---
>  drivers/resctrl/mpam_devices.c  |  6 +++---
>  drivers/resctrl/mpam_internal.h |  7 +++++++
>  drivers/resctrl/mpam_resctrl.c  | 15 +++++++++++++++
>  3 files changed, 25 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> index 303aacfcb9d6..4f5d908d02a9 100644
> --- a/drivers/resctrl/mpam_devices.c
> +++ b/drivers/resctrl/mpam_devices.c
> @@ -2544,7 +2544,7 @@ static void mpam_enable_once(void)
>  	       mpam_partid_max + 1, mpam_pmg_max + 1);
>  }
>  
> -static void mpam_reset_component_locked(struct mpam_component *comp)
> +void mpam_reset_component_locked(struct mpam_component *comp)
>  {
>  	struct mpam_vmsc *vmsc;
>  
> @@ -2568,7 +2568,7 @@ static void mpam_reset_component_locked(struct mpam_component *comp)
>  	}
>  }
>  
> -static void mpam_reset_class_locked(struct mpam_class *class)
> +void mpam_reset_class_locked(struct mpam_class *class)
>  {
>  	struct mpam_component *comp;
>  
> @@ -2580,7 +2580,7 @@ static void mpam_reset_class_locked(struct mpam_class *class)
>  		mpam_reset_component_locked(comp);
>  }
>  
> -static void mpam_reset_class(struct mpam_class *class)
> +void mpam_reset_class(struct mpam_class *class)
>  {
>  	cpus_read_lock();
>  	mpam_reset_class_locked(class);
> diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
> index 554e4887ba81..b9a739abb101 100644
> --- a/drivers/resctrl/mpam_internal.h
> +++ b/drivers/resctrl/mpam_internal.h
> @@ -389,6 +389,13 @@ extern u8 mpam_pmg_max;
>  void mpam_enable(struct work_struct *work);
>  void mpam_disable(struct work_struct *work);
>  
> +/* Reset all the RIS in a class, optionally while holding cpus_read_lock() */
> +void mpam_reset_class_locked(struct mpam_class *class);
> +void mpam_reset_class(struct mpam_class *class);

Not clear from this patch why we need to expose mpam_reset_class()

> +
> +/* Reset all the RIS in a component under cpus_read_lock() */
> +void mpam_reset_component_locked(struct mpam_component *comp);
> +
>  int mpam_apply_config(struct mpam_component *comp, u16 partid,
>  		      struct mpam_config *cfg);
>  
> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> index bc4f1c80eab5..d32e87002457 100644
> --- a/drivers/resctrl/mpam_resctrl.c
> +++ b/drivers/resctrl/mpam_resctrl.c
> @@ -167,6 +167,19 @@ static int mpam_resctrl_pick_domain_id(int cpu, struct mpam_component *comp)
>  	return comp->comp_id;
>  }
>  
> +void resctrl_arch_reset_all_ctrls(struct rdt_resource *r)
> +{
> +	struct mpam_resctrl_res *res;
> +
> +	lockdep_assert_cpus_held();
> +
> +	if (!mpam_is_enabled())
> +		return;
> +
> +	res = container_of(r, struct mpam_resctrl_res, resctrl_res);
> +	mpam_reset_class_locked(res->class);
> +}
> +
>  static void mpam_resctrl_domain_hdr_init(int cpu, struct mpam_component *comp,
>  					 struct rdt_domain_hdr *hdr)
>  {
> @@ -353,6 +366,8 @@ void mpam_resctrl_offline_cpu(unsigned int cpu)
>  
>  		ctrl_dom_empty = true;
>  		if (exposed_alloc_capable) {
> +			mpam_reset_component_locked(dom->ctrl_comp);
> +
>  			ctrl_d = &dom->resctrl_ctrl_dom;
>  			ctrl_dom_empty = mpam_resctrl_offline_domain_hdr(cpu, &ctrl_d->hdr);
>  			if (ctrl_dom_empty)

Re: [PATCH v2 18/45] arm_mpam: resctrl: Implement resctrl_arch_reset_all_ctrls()

[Ben Horgan]

Hi Jonathan,

On 1/5/26 17:51, Jonathan Cameron wrote:
> On Fri, 19 Dec 2025 18:11:20 +0000
> Ben Horgan <ben.horgan@arm.com> wrote:
> 
>> From: James Morse <james.morse@arm.com>
>>
>> We already have a helper for resetting an mpam class and component.  Hook
>> it up to resctrl_arch_reset_all_ctrls() and the domain offline path.
>>
>> Signed-off-by: James Morse <james.morse@arm.com>
>> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> I left all the context as my one comment on this is I don't see a reason
> to expose mpam_reset_class()  Only the _locked() variant ever seems to be
> used outside of mpam_devices.c
> 
>> ---

>> diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
>> index 554e4887ba81..b9a739abb101 100644
>> --- a/drivers/resctrl/mpam_internal.h
>> +++ b/drivers/resctrl/mpam_internal.h
>> @@ -389,6 +389,13 @@ extern u8 mpam_pmg_max;
>>  void mpam_enable(struct work_struct *work);
>>  void mpam_disable(struct work_struct *work);
>>  
>> +/* Reset all the RIS in a class, optionally while holding cpus_read_lock() */
>> +void mpam_reset_class_locked(struct mpam_class *class);
>> +void mpam_reset_class(struct mpam_class *class);
> 
> Not clear from this patch why we need to expose mpam_reset_class()

Good spot. That's not required in this series, so I will stop exposing it.


Thanks,

Ben

[PATCH v2 19/45] arm_mpam: resctrl: Add resctrl_arch_get_config()

[Ben Horgan]

From: James Morse <james.morse@arm.com>

Implement resctrl_arch_get_config() by testing the live configuration for a
CPOR bitmap. For any other configuration type return the default.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 drivers/resctrl/mpam_resctrl.c | 43 ++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index d32e87002457..607e5f41f9e7 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -167,6 +167,49 @@ static int mpam_resctrl_pick_domain_id(int cpu, struct mpam_component *comp)
 	return comp->comp_id;
 }
 
+u32 resctrl_arch_get_config(struct rdt_resource *r, struct rdt_ctrl_domain *d,
+			    u32 closid, enum resctrl_conf_type type)
+{
+	u32 partid;
+	struct mpam_config *cfg;
+	struct mpam_props *cprops;
+	struct mpam_resctrl_res *res;
+	struct mpam_resctrl_dom *dom;
+	enum mpam_device_features configured_by;
+
+	lockdep_assert_cpus_held();
+
+	if (!mpam_is_enabled())
+		return resctrl_get_default_ctrl(r);
+
+	res = container_of(r, struct mpam_resctrl_res, resctrl_res);
+	dom = container_of(d, struct mpam_resctrl_dom, resctrl_ctrl_dom);
+	cprops = &res->class->props;
+
+	partid = resctrl_get_config_index(closid, type);
+	cfg = &dom->ctrl_comp->cfg[partid];
+
+	switch (r->rid) {
+	case RDT_RESOURCE_L2:
+	case RDT_RESOURCE_L3:
+		configured_by = mpam_feat_cpor_part;
+		break;
+	default:
+		return resctrl_get_default_ctrl(r);
+	}
+
+	if (!r->alloc_capable || partid >= resctrl_arch_get_num_closid(r) ||
+	    !mpam_has_feature(configured_by, cfg))
+		return resctrl_get_default_ctrl(r);
+
+	switch (configured_by) {
+	case mpam_feat_cpor_part:
+		return cfg->cpbm;
+	default:
+		return resctrl_get_default_ctrl(r);
+	}
+}
+
 void resctrl_arch_reset_all_ctrls(struct rdt_resource *r)
 {
 	struct mpam_resctrl_res *res;
-- 
2.43.0

Re: [PATCH v2 19/45] arm_mpam: resctrl: Add resctrl_arch_get_config()

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:21 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> Implement resctrl_arch_get_config() by testing the live configuration for a
> CPOR bitmap. For any other configuration type return the default.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

[PATCH v2 20/45] arm_mpam: resctrl: Implement helpers to update configuration

[Ben Horgan]

From: James Morse <james.morse@arm.com>

resctrl has two helpers for updating the configuration.
resctrl_arch_update_one() updates a single value, and is used by the
software-controller to apply feedback to the bandwidth controls, it has to
be called on one of the CPUs in the resctrl:domain.

resctrl_arch_update_domains() copies multiple staged configurations, it can
be called from anywhere.

Both helpers should update any changes to the underlying hardware.

Implement resctrl_arch_update_domains() to use
resctrl_arch_update_one(). Neither need to be called on a specific CPU as
the mpam driver will send IPIs as needed.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
list_for_each_entry -> list_for_each_entry_rcu
return 0
Restrict scope of local variables
---
 drivers/resctrl/mpam_resctrl.c | 70 ++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 607e5f41f9e7..e5ec5438eca8 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -210,6 +210,76 @@ u32 resctrl_arch_get_config(struct rdt_resource *r, struct rdt_ctrl_domain *d,
 	}
 }
 
+int resctrl_arch_update_one(struct rdt_resource *r, struct rdt_ctrl_domain *d,
+			    u32 closid, enum resctrl_conf_type t, u32 cfg_val)
+{
+	u32 partid;
+	struct mpam_config cfg;
+	struct mpam_props *cprops;
+	struct mpam_resctrl_res *res;
+	struct mpam_resctrl_dom *dom;
+
+	lockdep_assert_cpus_held();
+	lockdep_assert_irqs_enabled();
+
+	/*
+	 * No need to check the CPU as mpam_apply_config() doesn't care, and
+	 * resctrl_arch_update_domains() relies on this.
+	 */
+	res = container_of(r, struct mpam_resctrl_res, resctrl_res);
+	dom = container_of(d, struct mpam_resctrl_dom, resctrl_ctrl_dom);
+	cprops = &res->class->props;
+
+	partid = resctrl_get_config_index(closid, t);
+	if (!r->alloc_capable || partid >= resctrl_arch_get_num_closid(r)) {
+		pr_debug("Not alloc capable or computed PARTID out of range\n");
+		return -EINVAL;
+	}
+
+       /*
+	* Copy the current config to avoid clearing other resources when the
+	* same component is exposed multiple times through resctrl.
+	*/
+	cfg = dom->ctrl_comp->cfg[partid];
+
+	switch (r->rid) {
+	case RDT_RESOURCE_L2:
+	case RDT_RESOURCE_L3:
+		cfg.cpbm = cfg_val;
+		mpam_set_feature(mpam_feat_cpor_part, &cfg);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return mpam_apply_config(dom->ctrl_comp, partid, &cfg);
+}
+
+int resctrl_arch_update_domains(struct rdt_resource *r, u32 closid)
+{
+	int err;
+	struct rdt_ctrl_domain *d;
+
+	lockdep_assert_cpus_held();
+	lockdep_assert_irqs_enabled();
+
+	list_for_each_entry_rcu(d, &r->ctrl_domains, hdr.list) {
+		for (enum resctrl_conf_type t = 0; t < CDP_NUM_TYPES; t++) {
+			struct resctrl_staged_config *cfg = &d->staged_config[t];
+
+			if (!cfg->have_new_ctrl)
+				continue;
+
+			err = resctrl_arch_update_one(r, d, closid, t,
+						      cfg->new_ctrl);
+			if (err)
+				return err;
+		}
+	}
+
+	return 0;
+}
+
 void resctrl_arch_reset_all_ctrls(struct rdt_resource *r)
 {
 	struct mpam_resctrl_res *res;
-- 
2.43.0

Re: [PATCH v2 20/45] arm_mpam: resctrl: Implement helpers to update configuration

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:22 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> resctrl has two helpers for updating the configuration.
> resctrl_arch_update_one() updates a single value, and is used by the
> software-controller to apply feedback to the bandwidth controls, it has to
> be called on one of the CPUs in the resctrl:domain.
> 
> resctrl_arch_update_domains() copies multiple staged configurations, it can
> be called from anywhere.
> 
> Both helpers should update any changes to the underlying hardware.
> 
> Implement resctrl_arch_update_domains() to use
> resctrl_arch_update_one(). Neither need to be called on a specific CPU as
> the mpam driver will send IPIs as needed.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
One trivial thing inline.

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> ---
> list_for_each_entry -> list_for_each_entry_rcu
> return 0
> Restrict scope of local variables
> ---
>  drivers/resctrl/mpam_resctrl.c | 70 ++++++++++++++++++++++++++++++++++
>  1 file changed, 70 insertions(+)
> 
> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> index 607e5f41f9e7..e5ec5438eca8 100644
> --- a/drivers/resctrl/mpam_resctrl.c
> +++ b/drivers/resctrl/mpam_resctrl.c
> @@ -210,6 +210,76 @@ u32 resctrl_arch_get_config(struct rdt_resource *r, struct rdt_ctrl_domain *d,
>  	}
>  }
>  
> +int resctrl_arch_update_one(struct rdt_resource *r, struct rdt_ctrl_domain *d,
> +			    u32 closid, enum resctrl_conf_type t, u32 cfg_val)
> +{
...

> +	partid = resctrl_get_config_index(closid, t);
> +	if (!r->alloc_capable || partid >= resctrl_arch_get_num_closid(r)) {
> +		pr_debug("Not alloc capable or computed PARTID out of range\n");
> +		return -EINVAL;
> +	}
> +
> +       /*

Spaces instead of a tab.

> +	* Copy the current config to avoid clearing other resources when the
> +	* same component is exposed multiple times through resctrl.
> +	*/

[PATCH v2 21/45] arm_mpam: resctrl: Add plumbing against arm64 task and cpu hooks

[Ben Horgan]

From: James Morse <james.morse@arm.com>

arm64 provides helpers for changing a tasks and a cpus mpam partid/pmg
values.

These are used to back a number of resctrl_arch_ functions. Connect them
up.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 drivers/resctrl/mpam_resctrl.c | 58 ++++++++++++++++++++++++++++++++++
 include/linux/arm_mpam.h       |  5 +++
 2 files changed, 63 insertions(+)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index e5ec5438eca8..2f72ca66fb8c 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -8,6 +8,7 @@
 #include <linux/cpu.h>
 #include <linux/cpumask.h>
 #include <linux/errno.h>
+#include <linux/limits.h>
 #include <linux/list.h>
 #include <linux/printk.h>
 #include <linux/rculist.h>
@@ -32,6 +33,8 @@ static DEFINE_MUTEX(domain_list_lock);
 static bool exposed_alloc_capable;
 static bool exposed_mon_capable;
 
+static bool cdp_enabled;
+
 bool resctrl_arch_alloc_capable(void)
 {
 	return exposed_alloc_capable;
@@ -52,6 +55,61 @@ u32 resctrl_arch_get_num_closid(struct rdt_resource *ignored)
 	return mpam_partid_max + 1;
 }
 
+void resctrl_arch_sched_in(struct task_struct *tsk)
+{
+	lockdep_assert_preemption_disabled();
+
+	mpam_thread_switch(tsk);
+}
+
+void resctrl_arch_set_cpu_default_closid_rmid(int cpu, u32 closid, u32 rmid)
+{
+	WARN_ON_ONCE(closid > U16_MAX);
+	WARN_ON_ONCE(rmid > U8_MAX);
+
+	if (!cdp_enabled) {
+		mpam_set_cpu_defaults(cpu, closid, closid, rmid, rmid);
+	} else {
+		/*
+		 * When CDP is enabled, resctrl halves the closid range and we
+		 * use odd/even partid for one closid.
+		 */
+		u32 partid_d = resctrl_get_config_index(closid, CDP_DATA);
+		u32 partid_i = resctrl_get_config_index(closid, CDP_CODE);
+
+		mpam_set_cpu_defaults(cpu, partid_d, partid_i, rmid, rmid);
+	}
+}
+
+void resctrl_arch_sync_cpu_closid_rmid(void *info)
+{
+	struct resctrl_cpu_defaults *r = info;
+
+	lockdep_assert_preemption_disabled();
+
+	if (r) {
+		resctrl_arch_set_cpu_default_closid_rmid(smp_processor_id(),
+							 r->closid, r->rmid);
+	}
+
+	resctrl_arch_sched_in(current);
+}
+
+void resctrl_arch_set_closid_rmid(struct task_struct *tsk, u32 closid, u32 rmid)
+{
+	WARN_ON_ONCE(closid > U16_MAX);
+	WARN_ON_ONCE(rmid > U8_MAX);
+
+	if (!cdp_enabled) {
+		mpam_set_task_partid_pmg(tsk, closid, closid, rmid, rmid);
+	} else {
+		u32 partid_d = resctrl_get_config_index(closid, CDP_DATA);
+		u32 partid_i = resctrl_get_config_index(closid, CDP_CODE);
+
+		mpam_set_task_partid_pmg(tsk, partid_d, partid_i, rmid, rmid);
+	}
+}
+
 struct rdt_resource *resctrl_arch_get_resource(enum resctrl_res_level l)
 {
 	if (l >= RDT_NUM_RESOURCES)
diff --git a/include/linux/arm_mpam.h b/include/linux/arm_mpam.h
index 2c7d1413a401..5a78299ec464 100644
--- a/include/linux/arm_mpam.h
+++ b/include/linux/arm_mpam.h
@@ -52,6 +52,11 @@ static inline int mpam_ris_create(struct mpam_msc *msc, u8 ris_idx,
 bool resctrl_arch_alloc_capable(void);
 bool resctrl_arch_mon_capable(void);
 
+void resctrl_arch_set_cpu_default_closid(int cpu, u32 closid);
+void resctrl_arch_set_closid_rmid(struct task_struct *tsk, u32 closid, u32 rmid);
+void resctrl_arch_set_cpu_default_closid_rmid(int cpu, u32 closid, u32 rmid);
+void resctrl_arch_sched_in(struct task_struct *tsk);
+
 /**
  * mpam_register_requestor() - Register a requestor with the MPAM driver
  * @partid_max:		The maximum PARTID value the requestor can generate.
-- 
2.43.0

Re: [PATCH v2 21/45] arm_mpam: resctrl: Add plumbing against arm64 task and cpu hooks

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:23 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> arm64 provides helpers for changing a tasks and a cpus mpam partid/pmg

task's and cpu's 
(at least I think that is the intent)
> values.
> 
> These are used to back a number of resctrl_arch_ functions. Connect them
> up.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

[PATCH v2 22/45] arm_mpam: resctrl: Add CDP emulation

[Ben Horgan]

From: James Morse <james.morse@arm.com>

Intel RDT's CDP feature allows the cache to use a different control value
depending on whether the accesses was for instruction fetch or a data
access. MPAM's equivalent feature is the other way up: the CPU assigns a
different partid label to traffic depending on whether it was instruction
fetch or a data access, which causes the cache to use a different control
value based solely on the partid.

MPAM can emulate CDP, with the side effect that the alternative partid is
seen by all MSC, it can't be enabled per-MSC.

Add the resctrl hooks to turn this on or off. Add the helpers that match a
closid against a task, which need to be aware that the value written to
hardware is not the same as the one resctrl is using.

Update the 'arm64_mpam_global_default' variable the arch code uses during
context switch to know when the per-cpu value should be used instead.

Awkwardly, the MB controls don't implement CDP. To emulate this, the MPAM
equivalent needs programming twice by the resctrl glue, as resctrl expects
the bandwidth controls to be applied independently for both data and
instruction-fetch.

CC: Dave Martin <Dave.Martin@arm.com>
CC: Amit Singh Tomar <amitsinght@marvell.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Changes since rfc:
Fail cdp initialisation if there is only one partid
Correct data/code confusion
---
 arch/arm64/include/asm/mpam.h  |   1 +
 drivers/resctrl/mpam_resctrl.c | 112 +++++++++++++++++++++++++++++++++
 include/linux/arm_mpam.h       |   3 +
 3 files changed, 116 insertions(+)

diff --git a/arch/arm64/include/asm/mpam.h b/arch/arm64/include/asm/mpam.h
index a7fd0656bf90..09ab1492695d 100644
--- a/arch/arm64/include/asm/mpam.h
+++ b/arch/arm64/include/asm/mpam.h
@@ -4,6 +4,7 @@
 #ifndef __ASM__MPAM_H
 #define __ASM__MPAM_H
 
+#include <linux/arm_mpam.h>
 #include <linux/bitfield.h>
 #include <linux/jump_label.h>
 #include <linux/percpu.h>
diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 2f72ca66fb8c..4275b1a85887 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -33,6 +33,10 @@ static DEFINE_MUTEX(domain_list_lock);
 static bool exposed_alloc_capable;
 static bool exposed_mon_capable;
 
+/*
+ * MPAM emulates CDP by setting different PARTID in the I/D fields of MPAM0_EL1.
+ * This applies globally to all traffic the CPU generates.
+ */
 static bool cdp_enabled;
 
 bool resctrl_arch_alloc_capable(void)
@@ -45,6 +49,67 @@ bool resctrl_arch_mon_capable(void)
 	return exposed_mon_capable;
 }
 
+bool resctrl_arch_get_cdp_enabled(enum resctrl_res_level rid)
+{
+	switch (rid) {
+	case RDT_RESOURCE_L2:
+	case RDT_RESOURCE_L3:
+		return cdp_enabled;
+	case RDT_RESOURCE_MBA:
+	default:
+		/*
+		 * x86's MBA control doesn't support CDP, so user-space doesn't
+		 * expect it.
+		 */
+		return false;
+	}
+}
+
+/**
+ * resctrl_reset_task_closids() - Reset the PARTID/PMG values for all tasks.
+ *
+ * At boot, all existing tasks use partid zero for D and I.
+ * To enable/disable CDP emulation, all these tasks need relabelling.
+ */
+static void resctrl_reset_task_closids(void)
+{
+	struct task_struct *p, *t;
+
+	read_lock(&tasklist_lock);
+	for_each_process_thread(p, t) {
+		resctrl_arch_set_closid_rmid(t, RESCTRL_RESERVED_CLOSID,
+					     RESCTRL_RESERVED_RMID);
+	}
+	read_unlock(&tasklist_lock);
+}
+
+int resctrl_arch_set_cdp_enabled(enum resctrl_res_level ignored, bool enable)
+{
+	u32 partid_i = RESCTRL_RESERVED_CLOSID, partid_d = RESCTRL_RESERVED_CLOSID;
+
+	cdp_enabled = enable;
+
+	if (enable) {
+		if (mpam_partid_max < 1)
+			return -EINVAL;
+
+		partid_d = resctrl_get_config_index(RESCTRL_RESERVED_CLOSID, CDP_DATA);
+		partid_i = resctrl_get_config_index(RESCTRL_RESERVED_CLOSID, CDP_CODE);
+	}
+
+	mpam_set_task_partid_pmg(current, partid_d, partid_i, 0, 0);
+	WRITE_ONCE(arm64_mpam_global_default, mpam_get_regval(current));
+
+	resctrl_reset_task_closids();
+
+	return 0;
+}
+
+static bool mpam_resctrl_hide_cdp(enum resctrl_res_level rid)
+{
+	return cdp_enabled && !resctrl_arch_get_cdp_enabled(rid);
+}
+
 /*
  * MSC may raise an error interrupt if it sees an out or range partid/pmg,
  * and go on to truncate the value. Regardless of what the hardware supports,
@@ -110,6 +175,30 @@ void resctrl_arch_set_closid_rmid(struct task_struct *tsk, u32 closid, u32 rmid)
 	}
 }
 
+bool resctrl_arch_match_closid(struct task_struct *tsk, u32 closid)
+{
+	u64 regval = mpam_get_regval(tsk);
+	u32 tsk_closid = FIELD_GET(MPAM0_EL1_PARTID_D, regval);
+
+	if (cdp_enabled)
+		tsk_closid >>= 1;
+
+	return tsk_closid == closid;
+}
+
+/* The task's pmg is not unique, the partid must be considered too */
+bool resctrl_arch_match_rmid(struct task_struct *tsk, u32 closid, u32 rmid)
+{
+	u64 regval = mpam_get_regval(tsk);
+	u32 tsk_closid = FIELD_GET(MPAM0_EL1_PARTID_D, regval);
+	u32 tsk_rmid = FIELD_GET(MPAM0_EL1_PMG_D, regval);
+
+	if (cdp_enabled)
+		tsk_closid >>= 1;
+
+	return (tsk_closid == closid) && (tsk_rmid == rmid);
+}
+
 struct rdt_resource *resctrl_arch_get_resource(enum resctrl_res_level l)
 {
 	if (l >= RDT_NUM_RESOURCES)
@@ -244,6 +333,14 @@ u32 resctrl_arch_get_config(struct rdt_resource *r, struct rdt_ctrl_domain *d,
 	dom = container_of(d, struct mpam_resctrl_dom, resctrl_ctrl_dom);
 	cprops = &res->class->props;
 
+	/*
+	 * When CDP is enabled, but the resource doesn't support it,
+	 * the control is cloned across both partids.
+	 * Pick one at random to read:
+	 */
+	if (mpam_resctrl_hide_cdp(r->rid))
+		type = CDP_DATA;
+
 	partid = resctrl_get_config_index(closid, type);
 	cfg = &dom->ctrl_comp->cfg[partid];
 
@@ -271,6 +368,7 @@ u32 resctrl_arch_get_config(struct rdt_resource *r, struct rdt_ctrl_domain *d,
 int resctrl_arch_update_one(struct rdt_resource *r, struct rdt_ctrl_domain *d,
 			    u32 closid, enum resctrl_conf_type t, u32 cfg_val)
 {
+	int err;
 	u32 partid;
 	struct mpam_config cfg;
 	struct mpam_props *cprops;
@@ -310,6 +408,20 @@ int resctrl_arch_update_one(struct rdt_resource *r, struct rdt_ctrl_domain *d,
 		return -EINVAL;
 	}
 
+	/*
+	 * When CDP is enabled, but the resource doesn't support it, we need to
+	 * apply the same configuration to the other partid.
+	 */
+	if (mpam_resctrl_hide_cdp(r->rid)) {
+		partid = resctrl_get_config_index(closid, CDP_CODE);
+		err = mpam_apply_config(dom->ctrl_comp, partid, &cfg);
+		if (err)
+			return err;
+
+		partid = resctrl_get_config_index(closid, CDP_DATA);
+		return mpam_apply_config(dom->ctrl_comp, partid, &cfg);
+	}
+
 	return mpam_apply_config(dom->ctrl_comp, partid, &cfg);
 }
 
diff --git a/include/linux/arm_mpam.h b/include/linux/arm_mpam.h
index 5a78299ec464..ba0312b55d9f 100644
--- a/include/linux/arm_mpam.h
+++ b/include/linux/arm_mpam.h
@@ -5,6 +5,7 @@
 #define __LINUX_ARM_MPAM_H
 
 #include <linux/acpi.h>
+#include <linux/resctrl_types.h>
 #include <linux/types.h>
 
 struct mpam_msc;
@@ -56,6 +57,8 @@ void resctrl_arch_set_cpu_default_closid(int cpu, u32 closid);
 void resctrl_arch_set_closid_rmid(struct task_struct *tsk, u32 closid, u32 rmid);
 void resctrl_arch_set_cpu_default_closid_rmid(int cpu, u32 closid, u32 rmid);
 void resctrl_arch_sched_in(struct task_struct *tsk);
+bool resctrl_arch_match_closid(struct task_struct *tsk, u32 closid);
+bool resctrl_arch_match_rmid(struct task_struct *tsk, u32 closid, u32 rmid);
 
 /**
  * mpam_register_requestor() - Register a requestor with the MPAM driver
-- 
2.43.0

Re: [PATCH v2 22/45] arm_mpam: resctrl: Add CDP emulation

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:24 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> Intel RDT's CDP feature allows the cache to use a different control value
> depending on whether the accesses was for instruction fetch or a data
> access. MPAM's equivalent feature is the other way up: the CPU assigns a
> different partid label to traffic depending on whether it was instruction
> fetch or a data access, which causes the cache to use a different control
> value based solely on the partid.
> 
> MPAM can emulate CDP, with the side effect that the alternative partid is
> seen by all MSC, it can't be enabled per-MSC.
> 
> Add the resctrl hooks to turn this on or off. Add the helpers that match a
> closid against a task, which need to be aware that the value written to
> hardware is not the same as the one resctrl is using.
> 
> Update the 'arm64_mpam_global_default' variable the arch code uses during
> context switch to know when the per-cpu value should be used instead.
> 
> Awkwardly, the MB controls don't implement CDP. To emulate this, the MPAM
> equivalent needs programming twice by the resctrl glue, as resctrl expects
> the bandwidth controls to be applied independently for both data and
> instruction-fetch.
> 
> CC: Dave Martin <Dave.Martin@arm.com>
> CC: Amit Singh Tomar <amitsinght@marvell.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>

Minor thing below.
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>


> diff --git a/include/linux/arm_mpam.h b/include/linux/arm_mpam.h
> index 5a78299ec464..ba0312b55d9f 100644
> --- a/include/linux/arm_mpam.h
> +++ b/include/linux/arm_mpam.h
> @@ -5,6 +5,7 @@
>  #define __LINUX_ARM_MPAM_H
>  
>  #include <linux/acpi.h>
> +#include <linux/resctrl_types.h>

This seems odd as nothing added to the header in this path appears to need it.
Maybe should be down in the c file or in a different patch?

>  #include <linux/types.h>
>  
>  struct mpam_msc;
> @@ -56,6 +57,8 @@ void resctrl_arch_set_cpu_default_closid(int cpu, u32 closid);
>  void resctrl_arch_set_closid_rmid(struct task_struct *tsk, u32 closid, u32 rmid);
>  void resctrl_arch_set_cpu_default_closid_rmid(int cpu, u32 closid, u32 rmid);
>  void resctrl_arch_sched_in(struct task_struct *tsk);
> +bool resctrl_arch_match_closid(struct task_struct *tsk, u32 closid);
> +bool resctrl_arch_match_rmid(struct task_struct *tsk, u32 closid, u32 rmid);
>  
>  /**
>   * mpam_register_requestor() - Register a requestor with the MPAM driver

Re: [PATCH v2 22/45] arm_mpam: resctrl: Add CDP emulation

[Ben Horgan]

Hi Jonathan,

On 1/5/26 18:07, Jonathan Cameron wrote:
> On Fri, 19 Dec 2025 18:11:24 +0000
> Ben Horgan <ben.horgan@arm.com> wrote:
> 
>> From: James Morse <james.morse@arm.com>
>>
>> Intel RDT's CDP feature allows the cache to use a different control value
>> depending on whether the accesses was for instruction fetch or a data
>> access. MPAM's equivalent feature is the other way up: the CPU assigns a
>> different partid label to traffic depending on whether it was instruction
>> fetch or a data access, which causes the cache to use a different control
>> value based solely on the partid.
>>
>> MPAM can emulate CDP, with the side effect that the alternative partid is
>> seen by all MSC, it can't be enabled per-MSC.
>>
>> Add the resctrl hooks to turn this on or off. Add the helpers that match a
>> closid against a task, which need to be aware that the value written to
>> hardware is not the same as the one resctrl is using.
>>
>> Update the 'arm64_mpam_global_default' variable the arch code uses during
>> context switch to know when the per-cpu value should be used instead.
>>
>> Awkwardly, the MB controls don't implement CDP. To emulate this, the MPAM
>> equivalent needs programming twice by the resctrl glue, as resctrl expects
>> the bandwidth controls to be applied independently for both data and
>> instruction-fetch.
>>
>> CC: Dave Martin <Dave.Martin@arm.com>
>> CC: Amit Singh Tomar <amitsinght@marvell.com>
>> Signed-off-by: James Morse <james.morse@arm.com>
>> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> 
> Minor thing below.
> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
> 
> 
>> diff --git a/include/linux/arm_mpam.h b/include/linux/arm_mpam.h
>> index 5a78299ec464..ba0312b55d9f 100644
>> --- a/include/linux/arm_mpam.h
>> +++ b/include/linux/arm_mpam.h
>> @@ -5,6 +5,7 @@
>>  #define __LINUX_ARM_MPAM_H
>>  
>>  #include <linux/acpi.h>
>> +#include <linux/resctrl_types.h>
> 
> This seems odd as nothing added to the header in this path appears to need it.
> Maybe should be down in the c file or in a different patch?

Yep, moved it to patch 33, arm_mpam: resctrl: Allow resctrl to allocate
monitors.

> 
>>  #include <linux/types.h>
>>  
>>  struct mpam_msc;
>> @@ -56,6 +57,8 @@ void resctrl_arch_set_cpu_default_closid(int cpu, u32 closid);
>>  void resctrl_arch_set_closid_rmid(struct task_struct *tsk, u32 closid, u32 rmid);
>>  void resctrl_arch_set_cpu_default_closid_rmid(int cpu, u32 closid, u32 rmid);
>>  void resctrl_arch_sched_in(struct task_struct *tsk);
>> +bool resctrl_arch_match_closid(struct task_struct *tsk, u32 closid);
>> +bool resctrl_arch_match_rmid(struct task_struct *tsk, u32 closid, u32 rmid);
>>  
>>  /**
>>   * mpam_register_requestor() - Register a requestor with the MPAM driver
> 

Thanks,

Ben

[PATCH v2 23/45] arm_mpam: resctrl: Add rmid index helpers

[Ben Horgan]

From: James Morse <james.morse@arm.com>

Because MPAM's pmg aren't identical to RDT's rmid, resctrl handles some
data structures by index. This allows x86 to map indexes to RMID, and MPAM
to map them to partid-and-pmg.

Add the helpers to do this.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Changes since rfc:
Use ~0U instead of ~0 in lhs of left shift
---
 drivers/resctrl/mpam_resctrl.c | 28 ++++++++++++++++++++++++++++
 include/linux/arm_mpam.h       |  3 +++
 2 files changed, 31 insertions(+)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 4275b1a85887..bdbc5504964b 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -120,6 +120,34 @@ u32 resctrl_arch_get_num_closid(struct rdt_resource *ignored)
 	return mpam_partid_max + 1;
 }
 
+u32 resctrl_arch_system_num_rmid_idx(void)
+{
+	u8 closid_shift = fls(mpam_pmg_max);
+	u32 num_partid = resctrl_arch_get_num_closid(NULL);
+
+	return num_partid << closid_shift;
+}
+
+u32 resctrl_arch_rmid_idx_encode(u32 closid, u32 rmid)
+{
+	u8 closid_shift = fls(mpam_pmg_max);
+
+	WARN_ON_ONCE(closid_shift > 8);
+
+	return (closid << closid_shift) | rmid;
+}
+
+void resctrl_arch_rmid_idx_decode(u32 idx, u32 *closid, u32 *rmid)
+{
+	u8 closid_shift = fls(mpam_pmg_max);
+	u32 pmg_mask = ~(~0U << closid_shift);
+
+	WARN_ON_ONCE(closid_shift > 8);
+
+	*closid = idx >> closid_shift;
+	*rmid = idx & pmg_mask;
+}
+
 void resctrl_arch_sched_in(struct task_struct *tsk)
 {
 	lockdep_assert_preemption_disabled();
diff --git a/include/linux/arm_mpam.h b/include/linux/arm_mpam.h
index ba0312b55d9f..385554ceb452 100644
--- a/include/linux/arm_mpam.h
+++ b/include/linux/arm_mpam.h
@@ -59,6 +59,9 @@ void resctrl_arch_set_cpu_default_closid_rmid(int cpu, u32 closid, u32 rmid);
 void resctrl_arch_sched_in(struct task_struct *tsk);
 bool resctrl_arch_match_closid(struct task_struct *tsk, u32 closid);
 bool resctrl_arch_match_rmid(struct task_struct *tsk, u32 closid, u32 rmid);
+u32 resctrl_arch_rmid_idx_encode(u32 closid, u32 rmid);
+void resctrl_arch_rmid_idx_decode(u32 idx, u32 *closid, u32 *rmid);
+u32 resctrl_arch_system_num_rmid_idx(void);
 
 /**
  * mpam_register_requestor() - Register a requestor with the MPAM driver
-- 
2.43.0

Re: [PATCH v2 23/45] arm_mpam: resctrl: Add rmid index helpers

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:25 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> Because MPAM's pmg aren't identical to RDT's rmid, resctrl handles some
> data structures by index. This allows x86 to map indexes to RMID, and MPAM
> to map them to partid-and-pmg.
> 
> Add the helpers to do this.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
one comment inline.
I messed around with GENMASK + field_prep()/field_get() - new
versions of these with no need for runtime constant masks, but
it ended up as not that much more readable than what you have here.

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
> ---
> Changes since rfc:
> Use ~0U instead of ~0 in lhs of left shift
> ---
>  drivers/resctrl/mpam_resctrl.c | 28 ++++++++++++++++++++++++++++
>  include/linux/arm_mpam.h       |  3 +++
>  2 files changed, 31 insertions(+)
> 
> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> index 4275b1a85887..bdbc5504964b 100644
> --- a/drivers/resctrl/mpam_resctrl.c
> +++ b/drivers/resctrl/mpam_resctrl.c
> @@ -120,6 +120,34 @@ u32 resctrl_arch_get_num_closid(struct rdt_resource *ignored)
>  	return mpam_partid_max + 1;
>  }
>  
> +u32 resctrl_arch_system_num_rmid_idx(void)
> +{
> +	u8 closid_shift = fls(mpam_pmg_max);
> +	u32 num_partid = resctrl_arch_get_num_closid(NULL);
> +
> +	return num_partid << closid_shift;

Given I think you restrict mpam_pmg_max to be power of 2 elsewhere,
doesn't this end up the same as something like
	return mpam_pmg_max * resctrl_arch_get_num_closid(NULL);
Maybe its worth keeping it in the form you have here as
it sort of provides documentation for how you pack those IDs

> +}

Re: [PATCH v2 23/45] arm_mpam: resctrl: Add rmid index helpers

[Ben Horgan]

Hi Jonathan,

On 1/6/26 11:21, Jonathan Cameron wrote:
> On Fri, 19 Dec 2025 18:11:25 +0000
> Ben Horgan <ben.horgan@arm.com> wrote:
> 
>> From: James Morse <james.morse@arm.com>
>>
>> Because MPAM's pmg aren't identical to RDT's rmid, resctrl handles some
>> data structures by index. This allows x86 to map indexes to RMID, and MPAM
>> to map them to partid-and-pmg.
>>
>> Add the helpers to do this.
>>
>> Signed-off-by: James Morse <james.morse@arm.com>
>> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> one comment inline.
> I messed around with GENMASK + field_prep()/field_get() - new
> versions of these with no need for runtime constant masks, but
> it ended up as not that much more readable than what you have here.
> 
> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
>> ---
>> Changes since rfc:
>> Use ~0U instead of ~0 in lhs of left shift
>> ---
>>  drivers/resctrl/mpam_resctrl.c | 28 ++++++++++++++++++++++++++++
>>  include/linux/arm_mpam.h       |  3 +++
>>  2 files changed, 31 insertions(+)
>>
>> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
>> index 4275b1a85887..bdbc5504964b 100644
>> --- a/drivers/resctrl/mpam_resctrl.c
>> +++ b/drivers/resctrl/mpam_resctrl.c
>> @@ -120,6 +120,34 @@ u32 resctrl_arch_get_num_closid(struct rdt_resource *ignored)
>>  	return mpam_partid_max + 1;
>>  }
>>  
>> +u32 resctrl_arch_system_num_rmid_idx(void)
>> +{
>> +	u8 closid_shift = fls(mpam_pmg_max);
>> +	u32 num_partid = resctrl_arch_get_num_closid(NULL);
>> +
>> +	return num_partid << closid_shift;
> 
> Given I think you restrict mpam_pmg_max to be power of 2 elsewhere,
> doesn't this end up the same as something like
> 	return mpam_pmg_max * resctrl_arch_get_num_closid(NULL);
> Maybe its worth keeping it in the form you have here as
> it sort of provides documentation for how you pack those IDs

We only warn if (mpam_pmg_max + 1) is a power of 2 and so I'll keep this
as it is, although yours is equivalent in the expected case.

> 
>> +}
> 

Thanks,

Ben

Re: [PATCH v2 23/45] arm_mpam: resctrl: Add rmid index helpers

[Jonathan Cameron]

On Tue, 6 Jan 2026 11:33:44 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> Hi Jonathan,
> 
> On 1/6/26 11:21, Jonathan Cameron wrote:
> > On Fri, 19 Dec 2025 18:11:25 +0000
> > Ben Horgan <ben.horgan@arm.com> wrote:
> >   
> >> From: James Morse <james.morse@arm.com>
> >>
> >> Because MPAM's pmg aren't identical to RDT's rmid, resctrl handles some
> >> data structures by index. This allows x86 to map indexes to RMID, and MPAM
> >> to map them to partid-and-pmg.
> >>
> >> Add the helpers to do this.
> >>
> >> Signed-off-by: James Morse <james.morse@arm.com>
> >> Signed-off-by: Ben Horgan <ben.horgan@arm.com>  
> > one comment inline.
> > I messed around with GENMASK + field_prep()/field_get() - new
> > versions of these with no need for runtime constant masks, but
> > it ended up as not that much more readable than what you have here.
> > 
> > Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>  
> >> ---
> >> Changes since rfc:
> >> Use ~0U instead of ~0 in lhs of left shift
> >> ---
> >>  drivers/resctrl/mpam_resctrl.c | 28 ++++++++++++++++++++++++++++
> >>  include/linux/arm_mpam.h       |  3 +++
> >>  2 files changed, 31 insertions(+)
> >>
> >> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> >> index 4275b1a85887..bdbc5504964b 100644
> >> --- a/drivers/resctrl/mpam_resctrl.c
> >> +++ b/drivers/resctrl/mpam_resctrl.c
> >> @@ -120,6 +120,34 @@ u32 resctrl_arch_get_num_closid(struct rdt_resource *ignored)
> >>  	return mpam_partid_max + 1;
> >>  }
> >>  
> >> +u32 resctrl_arch_system_num_rmid_idx(void)
> >> +{
> >> +	u8 closid_shift = fls(mpam_pmg_max);
> >> +	u32 num_partid = resctrl_arch_get_num_closid(NULL);
> >> +
> >> +	return num_partid << closid_shift;  
> > 
> > Given I think you restrict mpam_pmg_max to be power of 2 elsewhere,
> > doesn't this end up the same as something like
> > 	return mpam_pmg_max * resctrl_arch_get_num_closid(NULL);
> > Maybe its worth keeping it in the form you have here as
> > it sort of provides documentation for how you pack those IDs  
> 
> We only warn if (mpam_pmg_max + 1) is a power of 2 and so I'll keep this
> as it is, although yours is equivalent in the expected case.

Do the resulting 'holes' in the values that are valid here cause
trouble it isn't power of 2? 

> 
> >   
> >> +}  
> >   
> 
> Thanks,
> 
> Ben
> 
> 

Re: [PATCH v2 23/45] arm_mpam: resctrl: Add rmid index helpers

[Ben Horgan]

Hi Jonathan,

On 1/6/26 14:04, Jonathan Cameron wrote:
> On Tue, 6 Jan 2026 11:33:44 +0000
> Ben Horgan <ben.horgan@arm.com> wrote:
> 
>> Hi Jonathan,
>>
>> On 1/6/26 11:21, Jonathan Cameron wrote:
>>> On Fri, 19 Dec 2025 18:11:25 +0000
>>> Ben Horgan <ben.horgan@arm.com> wrote:
>>>   
>>>> From: James Morse <james.morse@arm.com>
>>>>
>>>> Because MPAM's pmg aren't identical to RDT's rmid, resctrl handles some
>>>> data structures by index. This allows x86 to map indexes to RMID, and MPAM
>>>> to map them to partid-and-pmg.
>>>>
>>>> Add the helpers to do this.
>>>>
>>>> Signed-off-by: James Morse <james.morse@arm.com>
>>>> Signed-off-by: Ben Horgan <ben.horgan@arm.com>  
>>> one comment inline.
>>> I messed around with GENMASK + field_prep()/field_get() - new
>>> versions of these with no need for runtime constant masks, but
>>> it ended up as not that much more readable than what you have here.
>>>
>>> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>  
>>>> ---
>>>> Changes since rfc:
>>>> Use ~0U instead of ~0 in lhs of left shift
>>>> ---
>>>>  drivers/resctrl/mpam_resctrl.c | 28 ++++++++++++++++++++++++++++
>>>>  include/linux/arm_mpam.h       |  3 +++
>>>>  2 files changed, 31 insertions(+)
>>>>
>>>> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
>>>> index 4275b1a85887..bdbc5504964b 100644
>>>> --- a/drivers/resctrl/mpam_resctrl.c
>>>> +++ b/drivers/resctrl/mpam_resctrl.c
>>>> @@ -120,6 +120,34 @@ u32 resctrl_arch_get_num_closid(struct rdt_resource *ignored)
>>>>  	return mpam_partid_max + 1;
>>>>  }
>>>>  
>>>> +u32 resctrl_arch_system_num_rmid_idx(void)
>>>> +{
>>>> +	u8 closid_shift = fls(mpam_pmg_max);
>>>> +	u32 num_partid = resctrl_arch_get_num_closid(NULL);
>>>> +
>>>> +	return num_partid << closid_shift;  
>>>
>>> Given I think you restrict mpam_pmg_max to be power of 2 elsewhere,
>>> doesn't this end up the same as something like
>>> 	return mpam_pmg_max * resctrl_arch_get_num_closid(NULL);
>>> Maybe its worth keeping it in the form you have here as
>>> it sort of provides documentation for how you pack those IDs  
>>
>> We only warn if (mpam_pmg_max + 1) is a power of 2 and so I'll keep this
>> as it is, although yours is equivalent in the expected case.
> 
> Do the resulting 'holes' in the values that are valid here cause
> trouble it isn't power of 2? 

Theoretically they are a problem, and if resctrl allocates them then we
would get invalid pmg values which can cause msc error interrupts.
However, I don't know of any platforms where pmg_max is more than 1.

Anyhow, I'll look into using multiplication in these rmid arch helpers
rather than just shifting to avoid leaving these holes.

> 
>>
>>>   
>>>> +}  
>>>   
>>
>> Thanks,
>>
>> Ben
>>
>>
> 

-- 
Thanks,

Ben

[PATCH v2 24/45] arm_mpam: resctrl: Convert to/from MPAMs fixed-point formats

[Ben Horgan]

From: Dave Martin <Dave.Martin@arm.com>

MPAM uses a fixed-point formats for some hardware controls.  Resctrl
provides the bandwidth controls as a percentage. Add helpers to convert
between these.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 drivers/resctrl/mpam_resctrl.c | 41 ++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index bdbc5504964b..a20656e49edc 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -10,6 +10,7 @@
 #include <linux/errno.h>
 #include <linux/limits.h>
 #include <linux/list.h>
+#include <linux/math.h>
 #include <linux/printk.h>
 #include <linux/rculist.h>
 #include <linux/resctrl.h>
@@ -246,6 +247,46 @@ static bool cache_has_usable_cpor(struct mpam_class *class)
 	return class->props.cpbm_wd <= 32;
 }
 
+/*
+ * Each fixed-point hardware value architecturally represents a range
+ * of values: the full range 0% - 100% is split contiguously into
+ * (1 << cprops->bwa_wd) equal bands.
+ * Find the nearest percentage value to the upper bound of the selected band:
+ */
+static u32 mbw_max_to_percent(u16 mbw_max, struct mpam_props *cprops)
+{
+	u32 val = mbw_max;
+
+	val >>= 16 - cprops->bwa_wd;
+	val += 1;
+	val *= MAX_MBA_BW;
+	val = DIV_ROUND_CLOSEST(val, 1 << cprops->bwa_wd);
+
+	return val;
+}
+
+/*
+ * Find the band whose upper bound is closest to the specified percentage.
+ *
+ * A round-to-nearest policy is followed here as a balanced compromise
+ * between unexpected under-commit of the resource (where the total of
+ * a set of resource allocations after conversion is less than the
+ * expected total, due to rounding of the individual converted
+ * percentages) and over-commit (where the total of the converted
+ * allocations is greater than expected).
+ */
+static u16 percent_to_mbw_max(u8 pc, struct mpam_props *cprops)
+{
+	u32 val = pc;
+
+	val <<= cprops->bwa_wd;
+	val = DIV_ROUND_CLOSEST(val, MAX_MBA_BW);
+	val = max(val, 1) - 1;
+	val <<= 16 - cprops->bwa_wd;
+
+	return val;
+}
+
 /* Test whether we can export MPAM_CLASS_CACHE:{2,3}? */
 static void mpam_resctrl_pick_caches(void)
 {
-- 
2.43.0

Re: [PATCH v2 24/45] arm_mpam: resctrl: Convert to/from MPAMs fixed-point formats

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:26 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: Dave Martin <Dave.Martin@arm.com>
> 
> MPAM uses a fixed-point formats for some hardware controls.  Resctrl
> provides the bandwidth controls as a percentage. Add helpers to convert
> between these.
> 
> Signed-off-by: Dave Martin <Dave.Martin@arm.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>

Perhaps it's just me, but I found this hard to check mostly because
of the spec being very light when describing this (that I could
find, maybe there is more somewhere else).

So whilst I'll give a tag, I'd like ideally a little more documentation,
particularly around the oddity of the left aligned field and max value
of bwa_wd being 16.

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> ---
>  drivers/resctrl/mpam_resctrl.c | 41 ++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
> 
> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> index bdbc5504964b..a20656e49edc 100644
> --- a/drivers/resctrl/mpam_resctrl.c
> +++ b/drivers/resctrl/mpam_resctrl.c
> @@ -10,6 +10,7 @@
>  #include <linux/errno.h>
>  #include <linux/limits.h>
>  #include <linux/list.h>
> +#include <linux/math.h>
>  #include <linux/printk.h>
>  #include <linux/rculist.h>
>  #include <linux/resctrl.h>
> @@ -246,6 +247,46 @@ static bool cache_has_usable_cpor(struct mpam_class *class)
>  	return class->props.cpbm_wd <= 32;
>  }
>  
> +/*
> + * Each fixed-point hardware value architecturally represents a range
> + * of values: the full range 0% - 100% is split contiguously into
> + * (1 << cprops->bwa_wd) equal bands.

This bit of the spec is really confusing.  I particularly like
BWA_WD being 6 bits but only allowed to take values up to 16. That took
me a while to spot as I couldn't work out what this was supposed to do if that
was 32.

Anyhow this is a request for a bit more documentation for this function such
as explaining the field is left aligned to bit 16.


> + * Find the nearest percentage value to the upper bound of the selected band:
> + */
> +static u32 mbw_max_to_percent(u16 mbw_max, struct mpam_props *cprops)
> +{
> +	u32 val = mbw_max;
> +
> +	val >>= 16 - cprops->bwa_wd;
> +	val += 1;
> +	val *= MAX_MBA_BW;
> +	val = DIV_ROUND_CLOSEST(val, 1 << cprops->bwa_wd);
> +
> +	return val;
> +}
> +
> +/*
> + * Find the band whose upper bound is closest to the specified percentage.
> + *
> + * A round-to-nearest policy is followed here as a balanced compromise
> + * between unexpected under-commit of the resource (where the total of
> + * a set of resource allocations after conversion is less than the
> + * expected total, due to rounding of the individual converted
> + * percentages) and over-commit (where the total of the converted
> + * allocations is greater than expected).
> + */
> +static u16 percent_to_mbw_max(u8 pc, struct mpam_props *cprops)
> +{
> +	u32 val = pc;
> +
> +	val <<= cprops->bwa_wd;
> +	val = DIV_ROUND_CLOSEST(val, MAX_MBA_BW);
> +	val = max(val, 1) - 1;
> +	val <<= 16 - cprops->bwa_wd;
> +
> +	return val;
> +}
> +
>  /* Test whether we can export MPAM_CLASS_CACHE:{2,3}? */
>  static void mpam_resctrl_pick_caches(void)
>  {

[PATCH v2 25/45] arm_mpam: resctrl: Add support for 'MB' resource

[Ben Horgan]

From: James Morse <james.morse@arm.com>

resctrl supports 'MB', as a percentage throttling of traffic somewhere
after the L3. This is the control that mba_sc uses, so ideally the class
chosen should be as close as possible to the counters used for mba_local.

MB's percentage control should be backed either with the fixed point
fraction MBW_MAX. The bandwidth portion bitmaps is not used as its tricky
to pick which bits to use to avoid contention, and may be possible to
expose this as something other than a percentage in the future.

CC: Zeng Heng <zengheng4@huawei.com>
Co-developed-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 drivers/resctrl/mpam_resctrl.c | 212 ++++++++++++++++++++++++++++++++-
 1 file changed, 211 insertions(+), 1 deletion(-)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index a20656e49edc..e376841c5596 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -247,6 +247,33 @@ static bool cache_has_usable_cpor(struct mpam_class *class)
 	return class->props.cpbm_wd <= 32;
 }
 
+static bool mba_class_use_mbw_max(struct mpam_props *cprops)
+{
+	return (mpam_has_feature(mpam_feat_mbw_max, cprops) &&
+		cprops->bwa_wd);
+}
+
+static bool class_has_usable_mba(struct mpam_props *cprops)
+{
+	return mba_class_use_mbw_max(cprops);
+}
+
+/*
+ * Calculate the worst-case percentage change from each implemented step
+ * in the control.
+ */
+static u32 get_mba_granularity(struct mpam_props *cprops)
+{
+	if (!mba_class_use_mbw_max(cprops))
+		return 0;
+
+	/*
+	 * bwa_wd is the number of bits implemented in the 0.xxx
+	 * fixed point fraction. 1 bit is 50%, 2 is 25% etc.
+	 */
+	return DIV_ROUND_UP(MAX_MBA_BW, 1 << cprops->bwa_wd);
+}
+
 /*
  * Each fixed-point hardware value architecturally represents a range
  * of values: the full range 0% - 100% is split contiguously into
@@ -287,6 +314,96 @@ static u16 percent_to_mbw_max(u8 pc, struct mpam_props *cprops)
 	return val;
 }
 
+static u32 get_mba_min(struct mpam_props *cprops)
+{
+	u32 val = 0;
+
+	if (mba_class_use_mbw_max(cprops))
+		val = mbw_max_to_percent(val, cprops);
+	else
+		WARN_ON_ONCE(1);
+
+	return val;
+}
+
+/* Find the L3 cache that has affinity with this CPU */
+static int find_l3_equivalent_bitmask(int cpu, cpumask_var_t tmp_cpumask)
+{
+	u32 cache_id = get_cpu_cacheinfo_id(cpu, 3);
+
+	lockdep_assert_cpus_held();
+
+	return mpam_get_cpumask_from_cache_id(cache_id, 3, tmp_cpumask);
+}
+
+/*
+ * topology_matches_l3() - Is the provided class the same shape as L3
+ * @victim:		The class we'd like to pretend is L3.
+ *
+ * resctrl expects all the world's a Xeon, and all counters are on the
+ * L3. We play fast and loose with this, mapping counters on other
+ * classes - provided the CPU->domain mapping is the same kind of shape.
+ *
+ * Using cacheinfo directly would make this work even if resctrl can't
+ * use the L3 - but cacheinfo can't tell us anything about offline CPUs.
+ * Using the L3 resctrl domain list also depends on CPUs being online.
+ * Using the mpam_class we picked for L3 so we can use its domain list
+ * assumes that there are MPAM controls on the L3.
+ * Instead, this path eventually uses the mpam_get_cpumask_from_cache_id()
+ * helper which can tell us about offline CPUs ... but getting the cache_id
+ * to start with relies on at least one CPU per L3 cache being online at
+ * boot.
+ *
+ * Walk the victim component list and compare the affinity mask with the
+ * corresponding L3. The topology matches if each victim:component's affinity
+ * mask is the same as the CPU's corresponding L3's. These lists/masks are
+ * computed from firmware tables so don't change at runtime.
+ */
+static bool topology_matches_l3(struct mpam_class *victim)
+{
+	int cpu, err;
+	struct mpam_component *victim_iter;
+	cpumask_var_t __free(free_cpumask_var) tmp_cpumask;
+
+	if (!alloc_cpumask_var(&tmp_cpumask, GFP_KERNEL))
+		return false;
+
+	guard(srcu)(&mpam_srcu);
+	list_for_each_entry_srcu(victim_iter, &victim->components, class_list,
+				 srcu_read_lock_held(&mpam_srcu)) {
+		if (cpumask_empty(&victim_iter->affinity)) {
+			pr_debug("class %u has CPU-less component %u - can't match L3!\n",
+				 victim->level, victim_iter->comp_id);
+			return false;
+		}
+
+		cpu = cpumask_any(&victim_iter->affinity);
+		if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
+			return false;
+
+		cpumask_clear(tmp_cpumask);
+		err = find_l3_equivalent_bitmask(cpu, tmp_cpumask);
+		if (err) {
+			pr_debug("Failed to find L3's equivalent component to class %u component %u\n",
+				 victim->level, victim_iter->comp_id);
+			return false;
+		}
+
+		/* Any differing bits in the affinity mask? */
+		if (!cpumask_equal(tmp_cpumask, &victim_iter->affinity)) {
+			pr_debug("class %u component %u has Mismatched CPU mask with L3 equivalent\n"
+				 "L3:%*pbl != victim:%*pbl\n",
+				 victim->level, victim_iter->comp_id,
+				 cpumask_pr_args(tmp_cpumask),
+				 cpumask_pr_args(&victim_iter->affinity));
+
+			return false;
+		}
+	}
+
+	return true;
+}
+
 /* Test whether we can export MPAM_CLASS_CACHE:{2,3}? */
 static void mpam_resctrl_pick_caches(void)
 {
@@ -329,10 +446,63 @@ static void mpam_resctrl_pick_caches(void)
 	}
 }
 
+static void mpam_resctrl_pick_mba(void)
+{
+	struct mpam_class *class, *candidate_class = NULL;
+	struct mpam_resctrl_res *res;
+
+	lockdep_assert_cpus_held();
+
+	guard(srcu)(&mpam_srcu);
+	list_for_each_entry_srcu(class, &mpam_classes, classes_list,
+				 srcu_read_lock_held(&mpam_srcu)) {
+		struct mpam_props *cprops = &class->props;
+
+		if (class->level < 3) {
+			pr_debug("class %u is before L3\n", class->level);
+			continue;
+		}
+
+		if (!class_has_usable_mba(cprops)) {
+			pr_debug("class %u has no bandwidth control\n",
+				 class->level);
+			continue;
+		}
+
+		if (!cpumask_equal(&class->affinity, cpu_possible_mask)) {
+			pr_debug("class %u has missing CPUs\n", class->level);
+			continue;
+		}
+
+		if (!topology_matches_l3(class)) {
+			pr_debug("class %u topology doesn't match L3\n",
+				 class->level);
+			continue;
+		}
+
+		/*
+		 * mba_sc reads the mbm_local counter, and waggles the MBA
+		 * controls. mbm_local is implicitly part of the L3, pick a
+		 * resource to be MBA that as close as possible to the L3.
+		 */
+		if (!candidate_class || class->level < candidate_class->level)
+			candidate_class = class;
+	}
+
+	if (candidate_class) {
+		pr_debug("selected class %u to back MBA\n",
+			 candidate_class->level);
+		res = &mpam_resctrl_controls[RDT_RESOURCE_MBA];
+		res->class = candidate_class;
+		exposed_alloc_capable = true;
+	}
+}
+
 static int mpam_resctrl_control_init(struct mpam_resctrl_res *res,
 				     enum resctrl_res_level type)
 {
 	struct mpam_class *class = res->class;
+	struct mpam_props *cprops = &class->props;
 	struct rdt_resource *r = &res->resctrl_res;
 
 	switch (r->rid) {
@@ -361,6 +531,20 @@ static int mpam_resctrl_control_init(struct mpam_resctrl_res *res,
 		 * 'all the bits' is the correct answer here.
 		 */
 		r->cache.shareable_bits = resctrl_get_default_ctrl(r);
+		break;
+	case RDT_RESOURCE_MBA:
+		r->alloc_capable = true;
+		r->schema_fmt = RESCTRL_SCHEMA_RANGE;
+		r->ctrl_scope = RESCTRL_L3_CACHE;
+
+		r->membw.delay_linear = true;
+		r->membw.throttle_mode = THREAD_THROTTLE_UNDEFINED;
+		r->membw.min_bw = get_mba_min(cprops);
+		r->membw.max_bw = MAX_MBA_BW;
+		r->membw.bw_gran = get_mba_granularity(cprops);
+
+		r->name = "MB";
+
 		break;
 	default:
 		break;
@@ -376,7 +560,17 @@ static int mpam_resctrl_pick_domain_id(int cpu, struct mpam_component *comp)
 	if (class->type == MPAM_CLASS_CACHE)
 		return comp->comp_id;
 
-	/* TODO: repaint domain ids to match the L3 domain ids */
+	if (topology_matches_l3(class)) {
+		/* Use the corresponding L3 component ID as the domain ID */
+		int id = get_cpu_cacheinfo_id(cpu, 3);
+
+		/* Implies topology_matches_l3() made a mistake */
+		if (WARN_ON_ONCE(id == -1))
+			return comp->comp_id;
+
+		return id;
+	}
+
 	/*
 	 * Otherwise, expose the ID used by the firmware table code.
 	 */
@@ -418,6 +612,12 @@ u32 resctrl_arch_get_config(struct rdt_resource *r, struct rdt_ctrl_domain *d,
 	case RDT_RESOURCE_L3:
 		configured_by = mpam_feat_cpor_part;
 		break;
+	case RDT_RESOURCE_MBA:
+		if (mpam_has_feature(mpam_feat_mbw_max, cprops)) {
+			configured_by = mpam_feat_mbw_max;
+			break;
+		}
+		fallthrough;
 	default:
 		return resctrl_get_default_ctrl(r);
 	}
@@ -429,6 +629,8 @@ u32 resctrl_arch_get_config(struct rdt_resource *r, struct rdt_ctrl_domain *d,
 	switch (configured_by) {
 	case mpam_feat_cpor_part:
 		return cfg->cpbm;
+	case mpam_feat_mbw_max:
+		return mbw_max_to_percent(cfg->mbw_max, cprops);
 	default:
 		return resctrl_get_default_ctrl(r);
 	}
@@ -473,6 +675,13 @@ int resctrl_arch_update_one(struct rdt_resource *r, struct rdt_ctrl_domain *d,
 		cfg.cpbm = cfg_val;
 		mpam_set_feature(mpam_feat_cpor_part, &cfg);
 		break;
+	case RDT_RESOURCE_MBA:
+		if (mpam_has_feature(mpam_feat_mbw_max, cprops)) {
+			cfg.mbw_max = percent_to_mbw_max(cfg_val, cprops);
+			mpam_set_feature(mpam_feat_mbw_max, &cfg);
+			break;
+		}
+		fallthrough;
 	default:
 		return -EINVAL;
 	}
@@ -754,6 +963,7 @@ int mpam_resctrl_setup(void)
 
 	/* Find some classes to use for controls */
 	mpam_resctrl_pick_caches();
+	mpam_resctrl_pick_mba();
 
 	/* Initialise the resctrl structures from the classes */
 	for (enum resctrl_res_level i = 0; i < RDT_NUM_RESOURCES; i++) {
-- 
2.43.0

Re: [PATCH v2 0/45] arm_mpam: Add KVM/arm64 and resctrl glue code

[Zeng Heng]

> One major departure from the previous snapshot branches referenced in the
> base driver series is that the same MPAM setting are used for kernel-space
> and user-space. That is, MPAM1_EL1 is set to the same value as MPAM0_EL1
> rather than keeping the default value. The advantages of this are that it
> is closer to the x86 model where the closid is globally applicable, all
> partids are usable from user-space and user-space can't bypass MPAM
> controls by doing the work in the kernel. However, this causes some
> priority inversion where a high priority task waits to take a mutex held by
> another whose resources are restricted by MPAM. It also adds some extra
> isb(). I would be interested in opinions/data on the policy for MPAM in
> kernel space, i.e how MPAM1_EL1 is set.

Another advantage is that, given the small size of the L2 cache,
frequent switching of MPAM configurations between kernel and user modes
can cause cache-capacity jitter, making it difficult to isolate
interference from noisy neighborhood.

However, in addition to the issues mentioned above, updating the
MPAM1_EL1 configuration also exposes interrupt handling to the MPAM
settings of the current task.

I still agree with the current modification of setting MPAM1_EL1 to the
same value as MPAM0_EL1. However, the ARM MPAM hardware supports more
flexible configuration schemes than x86 RDT and another approach is also
worth considering: Software can let a control group choose whether
kernel mode follows the user mode MPAM settings, or whether the kernel
mode configuration is delegated to the default control group, though
this may change the existing user interface.


Best Regards,
Zeng Heng

Re: [PATCH v2 25/45] arm_mpam: resctrl: Add support for 'MB' resource

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:27 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> resctrl supports 'MB', as a percentage throttling of traffic somewhere
> after the L3. This is the control that mba_sc uses, so ideally the class
> chosen should be as close as possible to the counters used for mba_local.
> 
> MB's percentage control should be backed either with the fixed point

either's "or" is missing.  (sentence should include the second choice)

> fraction MBW_MAX. The bandwidth portion bitmaps is not used as its tricky
> to pick which bits to use to avoid contention, and may be possible to
> expose this as something other than a percentage in the future.
> 
> CC: Zeng Heng <zengheng4@huawei.com>
> Co-developed-by: Dave Martin <Dave.Martin@arm.com>
> Signed-off-by: Dave Martin <Dave.Martin@arm.com>
> Signed-off-by: James Morse <james.morse@arm.com>>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>

As mentioned in earlier review I'd like an overview doc of the heuristics
used to map to the resctrl everything is a xeon view of the world.

At least some of our platforms are far enough from this view that the
heuristics fail (others can provide more info on that than I can).
That's fine as I'd rather not squash something inappropriate into a
viewpoint that doesn't fit. Better to leave those for later solutions!


Otherwise, just minor comments inline.

Jonathan

> ---
>  drivers/resctrl/mpam_resctrl.c | 212 ++++++++++++++++++++++++++++++++-
>  1 file changed, 211 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> index a20656e49edc..e376841c5596 100644
> --- a/drivers/resctrl/mpam_resctrl.c
> +++ b/drivers/resctrl/mpam_resctrl.c

...

> +static u32 get_mba_min(struct mpam_props *cprops)
> +{
> +	u32 val = 0;
> +
> +	if (mba_class_use_mbw_max(cprops))
> +		val = mbw_max_to_percent(val, cprops);
> +	else
> +		WARN_ON_ONCE(1);
> +
> +	return val;

I'd be tempted to handle the error case first to make
clear this is really just a sanity checking wrapper around the max_to_percent()
function.

	if (!mba_class_use_mbw_max(cprops)) {
		WARN_ON_ONCE(1);
		return 0;
	}

	return mbw_max_to_percent(val, cprops);

> +}

> +/*
> + * topology_matches_l3() - Is the provided class the same shape as L3
> + * @victim:		The class we'd like to pretend is L3.
> + *
> + * resctrl expects all the world's a Xeon, and all counters are on the
> + * L3. We play fast and loose with this, mapping counters on other
> + * classes - provided the CPU->domain mapping is the same kind of shape.
> + *
> + * Using cacheinfo directly would make this work even if resctrl can't
> + * use the L3 - but cacheinfo can't tell us anything about offline CPUs.
> + * Using the L3 resctrl domain list also depends on CPUs being online.
> + * Using the mpam_class we picked for L3 so we can use its domain list
> + * assumes that there are MPAM controls on the L3.
> + * Instead, this path eventually uses the mpam_get_cpumask_from_cache_id()
> + * helper which can tell us about offline CPUs ... but getting the cache_id
> + * to start with relies on at least one CPU per L3 cache being online at
> + * boot.

So the usual mess of maxcpus=1 breaks it for anything other than first L3?
I'm not entirely against that but it may be a little unexpected.

> + *
> + * Walk the victim component list and compare the affinity mask with the
> + * corresponding L3. The topology matches if each victim:component's affinity
> + * mask is the same as the CPU's corresponding L3's. These lists/masks are
> + * computed from firmware tables so don't change at runtime.
> + */
> +static bool topology_matches_l3(struct mpam_class *victim)



> +
>  static int mpam_resctrl_control_init(struct mpam_resctrl_res *res,
>  				     enum resctrl_res_level type)
>  {
>  	struct mpam_class *class = res->class;
> +	struct mpam_props *cprops = &class->props;
>  	struct rdt_resource *r = &res->resctrl_res;
>  
>  	switch (r->rid) {
> @@ -361,6 +531,20 @@ static int mpam_resctrl_control_init(struct mpam_resctrl_res *res,
>  		 * 'all the bits' is the correct answer here.
>  		 */
>  		r->cache.shareable_bits = resctrl_get_default_ctrl(r);
> +		break;
> +	case RDT_RESOURCE_MBA:
> +		r->alloc_capable = true;
> +		r->schema_fmt = RESCTRL_SCHEMA_RANGE;
> +		r->ctrl_scope = RESCTRL_L3_CACHE;
> +
> +		r->membw.delay_linear = true;
> +		r->membw.throttle_mode = THREAD_THROTTLE_UNDEFINED;
> +		r->membw.min_bw = get_mba_min(cprops);
> +		r->membw.max_bw = MAX_MBA_BW;
> +		r->membw.bw_gran = get_mba_granularity(cprops);
> +
> +		r->name = "MB";
> +

Probably should be consistent with either a blank line before break or not.
That might also make the diff a little nicer.

>  		break;
>  	default:
>  		break;

Re: [PATCH v2 25/45] arm_mpam: resctrl: Add support for 'MB' resource

[Ben Horgan]

Hi Jonathan,

On 1/6/26 12:19, Jonathan Cameron wrote:
> On Fri, 19 Dec 2025 18:11:27 +0000
> Ben Horgan <ben.horgan@arm.com> wrote:
> 
>> From: James Morse <james.morse@arm.com>
>>
>> resctrl supports 'MB', as a percentage throttling of traffic somewhere
>> after the L3. This is the control that mba_sc uses, so ideally the class
>> chosen should be as close as possible to the counters used for mba_local.
>>
>> MB's percentage control should be backed either with the fixed point
> 
> either's "or" is missing.  (sentence should include the second choice)
> 
>> fraction MBW_MAX. The bandwidth portion bitmaps is not used as its tricky
>> to pick which bits to use to avoid contention, and may be possible to
>> expose this as something other than a percentage in the future.
>>
>> CC: Zeng Heng <zengheng4@huawei.com>
>> Co-developed-by: Dave Martin <Dave.Martin@arm.com>
>> Signed-off-by: Dave Martin <Dave.Martin@arm.com>
>> Signed-off-by: James Morse <james.morse@arm.com>>
>> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> 
> As mentioned in earlier review I'd like an overview doc of the heuristics
> used to map to the resctrl everything is a xeon view of the world.
> 
> At least some of our platforms are far enough from this view that the
> heuristics fail (others can provide more info on that than I can).
> That's fine as I'd rather not squash something inappropriate into a
> viewpoint that doesn't fit. Better to leave those for later solutions!

Yes, this is still in the pipeline.

> 
> 
> Otherwise, just minor comments inline.
> 
> Jonathan
> 
>> ---
>>  drivers/resctrl/mpam_resctrl.c | 212 ++++++++++++++++++++++++++++++++-
>>  1 file changed, 211 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
>> index a20656e49edc..e376841c5596 100644
>> --- a/drivers/resctrl/mpam_resctrl.c
>> +++ b/drivers/resctrl/mpam_resctrl.c
> 
> ...
> 
>> +static u32 get_mba_min(struct mpam_props *cprops)
>> +{
>> +	u32 val = 0;
>> +
>> +	if (mba_class_use_mbw_max(cprops))
>> +		val = mbw_max_to_percent(val, cprops);
>> +	else
>> +		WARN_ON_ONCE(1);
>> +
>> +	return val;
> 
> I'd be tempted to handle the error case first to make
> clear this is really just a sanity checking wrapper around the max_to_percent()
> function.
> 
> 	if (!mba_class_use_mbw_max(cprops)) {
> 		WARN_ON_ONCE(1);
> 		return 0;
> 	}
> 
> 	return mbw_max_to_percent(val, cprops);

Sure, I've updated this.

> 
>> +}
> 
>> +/*
>> + * topology_matches_l3() - Is the provided class the same shape as L3
>> + * @victim:		The class we'd like to pretend is L3.
>> + *
>> + * resctrl expects all the world's a Xeon, and all counters are on the
>> + * L3. We play fast and loose with this, mapping counters on other
>> + * classes - provided the CPU->domain mapping is the same kind of shape.
>> + *
>> + * Using cacheinfo directly would make this work even if resctrl can't
>> + * use the L3 - but cacheinfo can't tell us anything about offline CPUs.
>> + * Using the L3 resctrl domain list also depends on CPUs being online.
>> + * Using the mpam_class we picked for L3 so we can use its domain list
>> + * assumes that there are MPAM controls on the L3.
>> + * Instead, this path eventually uses the mpam_get_cpumask_from_cache_id()
>> + * helper which can tell us about offline CPUs ... but getting the cache_id
>> + * to start with relies on at least one CPU per L3 cache being online at
>> + * boot.
> 
> So the usual mess of maxcpus=1 breaks it for anything other than first L3?
> I'm not entirely against that but it may be a little unexpected.

Yes but this doesn't really add any knew restriction as the mpam base
driver only enables mpam when all (known) msc have been probed and for
an msc on a cache we only ever access it from the cpus local to that cache.

> 
>> + *
>> + * Walk the victim component list and compare the affinity mask with the
>> + * corresponding L3. The topology matches if each victim:component's affinity
>> + * mask is the same as the CPU's corresponding L3's. These lists/masks are
>> + * computed from firmware tables so don't change at runtime.
>> + */
>> +static bool topology_matches_l3(struct mpam_class *victim)
> 
> 
> 
>> +
>>  static int mpam_resctrl_control_init(struct mpam_resctrl_res *res,
>>  				     enum resctrl_res_level type)
>>  {
>>  	struct mpam_class *class = res->class;
>> +	struct mpam_props *cprops = &class->props;
>>  	struct rdt_resource *r = &res->resctrl_res;
>>  
>>  	switch (r->rid) {
>> @@ -361,6 +531,20 @@ static int mpam_resctrl_control_init(struct mpam_resctrl_res *res,
>>  		 * 'all the bits' is the correct answer here.
>>  		 */
>>  		r->cache.shareable_bits = resctrl_get_default_ctrl(r);
>> +		break;
>> +	case RDT_RESOURCE_MBA:
>> +		r->alloc_capable = true;
>> +		r->schema_fmt = RESCTRL_SCHEMA_RANGE;
>> +		r->ctrl_scope = RESCTRL_L3_CACHE;
>> +
>> +		r->membw.delay_linear = true;
>> +		r->membw.throttle_mode = THREAD_THROTTLE_UNDEFINED;
>> +		r->membw.min_bw = get_mba_min(cprops);
>> +		r->membw.max_bw = MAX_MBA_BW;
>> +		r->membw.bw_gran = get_mba_granularity(cprops);
>> +
>> +		r->name = "MB";
>> +
> 
> Probably should be consistent with either a blank line before break or not.
> That might also make the diff a little nicer.

Dropped the blank line.

> 
>>  		break;
>>  	default:
>>  		break;
> 
> 

Thanks,

Ben

[PATCH v2 26/45] arm_mpam: resctrl: Add kunit test for control format conversions

[Ben Horgan]

From: Dave Martin <Dave.Martin@arm.com>

resctrl specifies the format of the control schemes, and these don't match
the hardware.

Some of the conversions are a bit hairy - add some kunit tests.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
[morse: squashed enough of Dave's fixes in here that it's his patch now!]
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 drivers/resctrl/mpam_resctrl.c      |   4 +
 drivers/resctrl/test_mpam_resctrl.c | 312 ++++++++++++++++++++++++++++
 2 files changed, 316 insertions(+)
 create mode 100644 drivers/resctrl/test_mpam_resctrl.c

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index e376841c5596..f8d8c241797a 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -1003,3 +1003,7 @@ int mpam_resctrl_setup(void)
 
 	return err;
 }
+
+#ifdef CONFIG_MPAM_KUNIT_TEST
+#include "test_mpam_resctrl.c"
+#endif
diff --git a/drivers/resctrl/test_mpam_resctrl.c b/drivers/resctrl/test_mpam_resctrl.c
new file mode 100644
index 000000000000..d0615aa7671c
--- /dev/null
+++ b/drivers/resctrl/test_mpam_resctrl.c
@@ -0,0 +1,312 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2025 Arm Ltd.
+/* This file is intended to be included into mpam_resctrl.c */
+
+#include <kunit/test.h>
+#include <linux/array_size.h>
+#include <linux/bits.h>
+#include <linux/math.h>
+#include <linux/sprintf.h>
+
+struct percent_value_case {
+	u8	pc;
+	u8	width;
+	u16	value;
+};
+
+/*
+ * Mysterious inscriptions taken from ARM DDI 0598D.b,
+ * "Arm Architecture Reference Manual Supplement - Memory System
+ * Resource Partitioning and Monitoring (MPAM), for A-profile
+ * architecture", Section 9.8, "About the fixed-point fractional
+ * format" (exact percentage entries only):
+ */
+static const struct percent_value_case percent_value_cases[] = {
+	/* Architectural cases: */
+	{   1,  8,    1 },	{   1, 12,  0x27 },	{   1, 16,  0x28e },
+	{  25,  8, 0x3f },	{  25, 12, 0x3ff },	{  25, 16, 0x3fff },
+	{  35,  8, 0x58 },	{  35, 12, 0x598 },	{  35, 16, 0x5998 },
+	{  45,  8, 0x72 },	{  45, 12, 0x732 },	{  45, 16, 0x7332 },
+	{  50,  8, 0x7f },	{  50, 12, 0x7ff },	{  50, 16, 0x7fff },
+	{  52,  8, 0x84 },	{  52, 12, 0x850 },	{  52, 16, 0x851d },
+	{  55,  8, 0x8b },	{  55, 12, 0x8cb },	{  55, 16, 0x8ccb },
+	{  58,  8, 0x93 },	{  58, 12, 0x946 },	{  58, 16, 0x9479 },
+	{  75,  8, 0xbf },	{  75, 12, 0xbff },	{  75, 16, 0xbfff },
+	{  88,  8, 0xe0 },	{  88, 12, 0xe13 },	{  88, 16, 0xe146 },
+	{  95,  8, 0xf2 },	{  95, 12, 0xf32 },	{  95, 16, 0xf332 },
+	{ 100,  8, 0xff },	{ 100, 12, 0xfff },	{ 100, 16, 0xffff },
+
+};
+
+static void test_percent_value_desc(const struct percent_value_case *param,
+				    char *desc)
+{
+	snprintf(desc, KUNIT_PARAM_DESC_SIZE,
+		 "pc=%d, width=%d, value=0x%.*x\n",
+		 param->pc, param->width,
+		 DIV_ROUND_UP(param->width, 4), param->value);
+}
+
+KUNIT_ARRAY_PARAM(test_percent_value, percent_value_cases,
+		  test_percent_value_desc);
+
+struct percent_value_test_info {
+	u32 pc;			/* result of value-to-percent conversion */
+	u32 value;		/* result of percent-to-value conversion */
+	u32 max_value;		/* maximum raw value allowed by test params */
+	unsigned int shift;	/* promotes raw testcase value to 16 bits */
+};
+
+/*
+ * Convert a reference percentage to a fixed-point MAX value and
+ * vice-versa, based on param (not test->param_value!)
+ */
+static void __prepare_percent_value_test(struct kunit *test,
+					 struct percent_value_test_info *res,
+					 const struct percent_value_case *param)
+{
+	struct mpam_props fake_props = { };
+
+	/* Reject bogus test parameters that would break the tests: */
+	KUNIT_ASSERT_GE(test, param->width, 1);
+	KUNIT_ASSERT_LE(test, param->width, 16);
+	KUNIT_ASSERT_LT(test, param->value, 1 << param->width);
+
+	mpam_set_feature(mpam_feat_mbw_max, &fake_props);
+	fake_props.bwa_wd = param->width;
+
+	res->shift = 16 - param->width;
+	res->max_value = GENMASK_U32(param->width - 1, 0);
+	res->value = percent_to_mbw_max(param->pc, &fake_props);
+	res->pc = mbw_max_to_percent(param->value << res->shift, &fake_props);
+}
+
+static void test_get_mba_granularity(struct kunit *test)
+{
+	int ret;
+	struct mpam_props fake_props = { };
+
+	/* Use MBW_MAX */
+	mpam_set_feature(mpam_feat_mbw_max, &fake_props);
+
+	fake_props.bwa_wd = 0;
+	KUNIT_EXPECT_FALSE(test, mba_class_use_mbw_max(&fake_props));
+
+	fake_props.bwa_wd = 1;
+	KUNIT_EXPECT_TRUE(test, mba_class_use_mbw_max(&fake_props));
+
+	/* Architectural maximum: */
+	fake_props.bwa_wd = 16;
+	KUNIT_EXPECT_TRUE(test, mba_class_use_mbw_max(&fake_props));
+
+	/* No usable control... */
+	fake_props.bwa_wd = 0;
+	ret = get_mba_granularity(&fake_props);
+	KUNIT_EXPECT_EQ(test, ret, 0);
+
+	fake_props.bwa_wd = 1;
+	ret = get_mba_granularity(&fake_props);
+	KUNIT_EXPECT_EQ(test, ret, 50);	/* DIV_ROUND_UP(100, 1 << 1)% = 50% */
+
+	fake_props.bwa_wd = 2;
+	ret = get_mba_granularity(&fake_props);
+	KUNIT_EXPECT_EQ(test, ret, 25);	/* DIV_ROUND_UP(100, 1 << 2)% = 25% */
+
+	fake_props.bwa_wd = 3;
+	ret = get_mba_granularity(&fake_props);
+	KUNIT_EXPECT_EQ(test, ret, 13);	/* DIV_ROUND_UP(100, 1 << 3)% = 13% */
+
+	fake_props.bwa_wd = 6;
+	ret = get_mba_granularity(&fake_props);
+	KUNIT_EXPECT_EQ(test, ret, 2);	/* DIV_ROUND_UP(100, 1 << 6)% = 2% */
+
+	fake_props.bwa_wd = 7;
+	ret = get_mba_granularity(&fake_props);
+	KUNIT_EXPECT_EQ(test, ret, 1);	/* DIV_ROUND_UP(100, 1 << 7)% = 1% */
+
+	/* Granularity saturates at 1% */
+	fake_props.bwa_wd = 16; /* architectural maximum */
+	ret = get_mba_granularity(&fake_props);
+	KUNIT_EXPECT_EQ(test, ret, 1);	/* DIV_ROUND_UP(100, 1 << 16)% = 1% */
+}
+
+static void test_mbw_max_to_percent(struct kunit *test)
+{
+	const struct percent_value_case *param = test->param_value;
+	struct percent_value_test_info res;
+
+	/*
+	 * Since the reference values in percent_value_cases[] all
+	 * correspond to exact percentages, round-to-nearest will
+	 * always give the exact percentage back when the MPAM max
+	 * value has precision of 0.5% or finer.  (Always true for the
+	 * reference data, since they all specify 8 bits or more of
+	 * precision.
+	 *
+	 * So, keep it simple and demand an exact match:
+	 */
+	__prepare_percent_value_test(test, &res, param);
+	KUNIT_EXPECT_EQ(test, res.pc, param->pc);
+}
+
+static void test_percent_to_mbw_max(struct kunit *test)
+{
+	const struct percent_value_case *param = test->param_value;
+	struct percent_value_test_info res;
+
+	__prepare_percent_value_test(test, &res, param);
+
+	KUNIT_EXPECT_GE(test, res.value, param->value << res.shift);
+	KUNIT_EXPECT_LE(test, res.value, (param->value + 1) << res.shift);
+	KUNIT_EXPECT_LE(test, res.value, res.max_value << res.shift);
+
+	/* No flexibility allowed for 0% and 100%! */
+
+	if (param->pc == 0)
+		KUNIT_EXPECT_EQ(test, res.value, 0);
+
+	if (param->pc == 100)
+		KUNIT_EXPECT_EQ(test, res.value, res.max_value << res.shift);
+}
+
+static const void *test_all_bwa_wd_gen_params(struct kunit *test, const void *prev,
+					      char *desc)
+{
+	uintptr_t param = (uintptr_t)prev;
+
+	if (param > 15)
+		return NULL;
+
+	param++;
+
+	snprintf(desc, KUNIT_PARAM_DESC_SIZE, "wd=%u\n", (unsigned int)param);
+
+	return (void *)param;
+}
+
+static unsigned int test_get_bwa_wd(struct kunit *test)
+{
+	uintptr_t param = (uintptr_t)test->param_value;
+
+	KUNIT_ASSERT_GE(test, param, 1);
+	KUNIT_ASSERT_LE(test, param, 16);
+
+	return param;
+}
+
+static void test_mbw_max_to_percent_limits(struct kunit *test)
+{
+	struct mpam_props fake_props = {0};
+	u32 max_value;
+
+	mpam_set_feature(mpam_feat_mbw_max, &fake_props);
+	fake_props.bwa_wd = test_get_bwa_wd(test);
+	max_value = GENMASK(15, 16 - fake_props.bwa_wd);
+
+	KUNIT_EXPECT_EQ(test, mbw_max_to_percent(max_value, &fake_props),
+			MAX_MBA_BW);
+	KUNIT_EXPECT_EQ(test, mbw_max_to_percent(0, &fake_props),
+			get_mba_min(&fake_props));
+
+	/*
+	 * Rounding policy dependent 0% sanity-check:
+	 * With round-to-nearest, the minimum mbw_max value really
+	 * should map to 0% if there are at least 200 steps.
+	 * (100 steps may be enough for some other rounding policies.)
+	 */
+	if (fake_props.bwa_wd >= 8)
+		KUNIT_EXPECT_EQ(test, mbw_max_to_percent(0, &fake_props), 0);
+
+	if (fake_props.bwa_wd < 8 &&
+	    mbw_max_to_percent(0, &fake_props) == 0)
+		kunit_warn(test, "wd=%d: Testsuite/driver Rounding policy mismatch?",
+			   fake_props.bwa_wd);
+}
+
+/*
+ * Check that converting a percentage to mbw_max and back again (or, as
+ * appropriate, vice-versa) always restores the original value:
+ */
+static void test_percent_max_roundtrip_stability(struct kunit *test)
+{
+	struct mpam_props fake_props = {0};
+	unsigned int shift;
+	u32 pc, max, pc2, max2;
+
+	mpam_set_feature(mpam_feat_mbw_max, &fake_props);
+	fake_props.bwa_wd = test_get_bwa_wd(test);
+	shift = 16 - fake_props.bwa_wd;
+
+	/*
+	 * Converting a valid value from the coarser scale to the finer
+	 * scale and back again must yield the original value:
+	 */
+	if (fake_props.bwa_wd >= 7) {
+		/* More than 100 steps: only test exact pc values: */
+		for (pc = get_mba_min(&fake_props); pc <= MAX_MBA_BW; pc++) {
+			max = percent_to_mbw_max(pc, &fake_props);
+			pc2 = mbw_max_to_percent(max, &fake_props);
+			KUNIT_EXPECT_EQ(test, pc2, pc);
+		}
+	} else {
+		/* Fewer than 100 steps: only test exact mbw_max values: */
+		for (max = 0; max < 1 << 16; max += 1 << shift) {
+			pc = mbw_max_to_percent(max, &fake_props);
+			max2 = percent_to_mbw_max(pc, &fake_props);
+			KUNIT_EXPECT_EQ(test, max2, max);
+		}
+	}
+}
+
+static void test_percent_to_max_rounding(struct kunit *test)
+{
+	const struct percent_value_case *param = test->param_value;
+	unsigned int num_rounded_up = 0, total = 0;
+	struct percent_value_test_info res;
+
+	for (param = percent_value_cases, total = 0;
+	     param < &percent_value_cases[ARRAY_SIZE(percent_value_cases)];
+	     param++, total++) {
+		__prepare_percent_value_test(test, &res, param);
+		if (res.value > param->value << res.shift)
+			num_rounded_up++;
+	}
+
+	/*
+	 * The MPAM driver applies a round-to-nearest policy, whereas a
+	 * round-down policy seems to have been applied in the
+	 * reference table from which the test vectors were selected.
+	 *
+	 * For a large and well-distributed suite of test vectors,
+	 * about half should be rounded up and half down compared with
+	 * the reference table.  The actual test vectors are few in
+	 * number and probably not very well distributed however, so
+	 * tolerate a round-up rate of between 1/4 and 3/4 before
+	 * crying foul:
+	 */
+
+	kunit_info(test, "Round-up rate: %u%% (%u/%u)\n",
+		   DIV_ROUND_CLOSEST(num_rounded_up * 100, total),
+		   num_rounded_up, total);
+
+	KUNIT_EXPECT_GE(test, 4 * num_rounded_up, 1 * total);
+	KUNIT_EXPECT_LE(test, 4 * num_rounded_up, 3 * total);
+}
+
+static struct kunit_case mpam_resctrl_test_cases[] = {
+	KUNIT_CASE(test_get_mba_granularity),
+	KUNIT_CASE_PARAM(test_mbw_max_to_percent, test_percent_value_gen_params),
+	KUNIT_CASE_PARAM(test_percent_to_mbw_max, test_percent_value_gen_params),
+	KUNIT_CASE_PARAM(test_mbw_max_to_percent_limits, test_all_bwa_wd_gen_params),
+	KUNIT_CASE(test_percent_to_max_rounding),
+	KUNIT_CASE_PARAM(test_percent_max_roundtrip_stability,
+			 test_all_bwa_wd_gen_params),
+	{}
+};
+
+static struct kunit_suite mpam_resctrl_test_suite = {
+	.name = "mpam_resctrl_test_suite",
+	.test_cases = mpam_resctrl_test_cases,
+};
+
+kunit_test_suites(&mpam_resctrl_test_suite);
-- 
2.43.0

Re: [PATCH v2 26/45] arm_mpam: resctrl: Add kunit test for control format conversions

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:28 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: Dave Martin <Dave.Martin@arm.com>
> 
> resctrl specifies the format of the control schemes, and these don't match
> the hardware.
> 
> Some of the conversions are a bit hairy - add some kunit tests.
> 
> Signed-off-by: Dave Martin <Dave.Martin@arm.com>
> [morse: squashed enough of Dave's fixes in here that it's his patch now!]
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
I took a fairly quick look at these and they seem sane.
Very valuable to have these tests.

Trivial stuff below and a request to carry the reference over to the
code rather than just having it in the tests.

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> diff --git a/drivers/resctrl/test_mpam_resctrl.c b/drivers/resctrl/test_mpam_resctrl.c
> new file mode 100644
> index 000000000000..d0615aa7671c
> --- /dev/null
> +++ b/drivers/resctrl/test_mpam_resctrl.c

> +/*
> + * Mysterious inscriptions taken from ARM DDI 0598D.b,
> + * "Arm Architecture Reference Manual Supplement - Memory System
> + * Resource Partitioning and Monitoring (MPAM), for A-profile
> + * architecture", Section 9.8, "About the fixed-point fractional
> + * format" (exact percentage entries only):

This is the reference I'd like alongside the conversion code.

> + */
> +static const struct percent_value_case percent_value_cases[] = {
> +	/* Architectural cases: */
> +	{   1,  8,    1 },	{   1, 12,  0x27 },	{   1, 16,  0x28e },
> +	{  25,  8, 0x3f },	{  25, 12, 0x3ff },	{  25, 16, 0x3fff },
> +	{  35,  8, 0x58 },	{  35, 12, 0x598 },	{  35, 16, 0x5998 },
> +	{  45,  8, 0x72 },	{  45, 12, 0x732 },	{  45, 16, 0x7332 },
> +	{  50,  8, 0x7f },	{  50, 12, 0x7ff },	{  50, 16, 0x7fff },
> +	{  52,  8, 0x84 },	{  52, 12, 0x850 },	{  52, 16, 0x851d },
> +	{  55,  8, 0x8b },	{  55, 12, 0x8cb },	{  55, 16, 0x8ccb },
> +	{  58,  8, 0x93 },	{  58, 12, 0x946 },	{  58, 16, 0x9479 },
> +	{  75,  8, 0xbf },	{  75, 12, 0xbff },	{  75, 16, 0xbfff },
> +	{  88,  8, 0xe0 },	{  88, 12, 0xe13 },	{  88, 16, 0xe146 },
> +	{  95,  8, 0xf2 },	{  95, 12, 0xf32 },	{  95, 16, 0xf332 },
> +	{ 100,  8, 0xff },	{ 100, 12, 0xfff },	{ 100, 16, 0xffff },
> +
This blank line doesn't add anything.

> +};
> +
> +static void test_percent_value_desc(const struct percent_value_case *param,
> +				    char *desc)
> +{
> +	snprintf(desc, KUNIT_PARAM_DESC_SIZE,
> +		 "pc=%d, width=%d, value=0x%.*x\n",
> +		 param->pc, param->width,
> +		 DIV_ROUND_UP(param->width, 4), param->value);
> +}

[PATCH v2 27/45] arm_mpam: resctrl: Add support for csu counters

[Ben Horgan]

From: James Morse <james.morse@arm.com>

resctrl exposes a counter via a file named llc_occupancy. This isn't really
a counter as its value goes up and down, this is a snapshot of the cache
storage usage monitor.

Add some picking code to find a cache as close as possible to the L3 that
supports the CSU monitor.

If there is an L3, but it doesn't have any controls, force the L3 resource
to exist. The existing topology_matches_l3() and
mpam_resctrl_domain_hdr_init() code will ensure this looks like the L3,
even if the class belongs to a later cache.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Changes since rfc:
Allow csu counters however many partid or pmg there are
else if -> if
reduce scope of local variables
drop has_csu
---
 drivers/resctrl/mpam_internal.h |   6 ++
 drivers/resctrl/mpam_resctrl.c  | 148 ++++++++++++++++++++++++++++++++
 2 files changed, 154 insertions(+)

diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index b9a739abb101..9cb9eb97893b 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -345,6 +345,12 @@ struct mpam_resctrl_res {
 	struct rdt_resource	resctrl_res;
 };
 
+struct mpam_resctrl_mon {
+	struct mpam_class	*class;
+
+	/* per-class data that resctrl needs will live here */
+};
+
 static inline int mpam_alloc_csu_mon(struct mpam_class *class)
 {
 	struct mpam_props *cprops = &class->props;
diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index f8d8c241797a..5fde610cc9d7 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -31,6 +31,16 @@ static struct mpam_resctrl_res mpam_resctrl_controls[RDT_NUM_RESOURCES];
 /* The lock for modifying resctrl's domain lists from cpuhp callbacks. */
 static DEFINE_MUTEX(domain_list_lock);
 
+/*
+ * The classes we've picked to map to resctrl events.
+ * Resctrl believes all the worlds a Xeon, and these are all on the L3. This
+ * array lets us find the actual class backing the event counters. e.g.
+ * the only memory bandwidth counters may be on the memory controller, but to
+ * make use of them, we pretend they are on L3.
+ * Class pointer may be NULL.
+ */
+static struct mpam_resctrl_mon mpam_resctrl_counters[QOS_NUM_EVENTS];
+
 static bool exposed_alloc_capable;
 static bool exposed_mon_capable;
 
@@ -258,6 +268,28 @@ static bool class_has_usable_mba(struct mpam_props *cprops)
 	return mba_class_use_mbw_max(cprops);
 }
 
+static bool cache_has_usable_csu(struct mpam_class *class)
+{
+	struct mpam_props *cprops;
+
+	if (!class)
+		return false;
+
+	cprops = &class->props;
+
+	if (!mpam_has_feature(mpam_feat_msmon_csu, cprops))
+		return false;
+
+	/*
+	 * CSU counters settle on the value, so we can get away with
+	 * having only one.
+	 */
+	if (!cprops->num_csu_mon)
+		return false;
+
+	return true;
+}
+
 /*
  * Calculate the worst-case percentage change from each implemented step
  * in the control.
@@ -498,6 +530,64 @@ static void mpam_resctrl_pick_mba(void)
 	}
 }
 
+static void counter_update_class(enum resctrl_event_id evt_id,
+				 struct mpam_class *class)
+{
+	struct mpam_class *existing_class = mpam_resctrl_counters[evt_id].class;
+
+	if (existing_class) {
+		if (class->level == 3) {
+			pr_debug("Existing class is L3 - L3 wins\n");
+			return;
+		}
+
+		if (existing_class->level < class->level) {
+			pr_debug("Existing class is closer to L3, %u versus %u - closer is better\n",
+				 existing_class->level, class->level);
+			return;
+		}
+	}
+
+	mpam_resctrl_counters[evt_id].class = class;
+	exposed_mon_capable = true;
+}
+
+static void mpam_resctrl_pick_counters(void)
+{
+	struct mpam_class *class;
+
+	lockdep_assert_cpus_held();
+
+	guard(srcu)(&mpam_srcu);
+	list_for_each_entry_srcu(class, &mpam_classes, classes_list,
+				 srcu_read_lock_held(&mpam_srcu)) {
+		if (class->level < 3) {
+			pr_debug("class %u is before L3", class->level);
+			continue;
+		}
+
+		if (!cpumask_equal(&class->affinity, cpu_possible_mask)) {
+			pr_debug("class %u does not cover all CPUs",
+				 class->level);
+			continue;
+		}
+
+		if (cache_has_usable_csu(class) && topology_matches_l3(class)) {
+			pr_debug("class %u has usable CSU, and matches L3 topology",
+				 class->level);
+
+			/* CSU counters only make sense on a cache. */
+			switch (class->type) {
+			case MPAM_CLASS_CACHE:
+				counter_update_class(QOS_L3_OCCUP_EVENT_ID, class);
+				return;
+			default:
+				return;
+			}
+		}
+	}
+}
+
 static int mpam_resctrl_control_init(struct mpam_resctrl_res *res,
 				     enum resctrl_res_level type)
 {
@@ -577,6 +667,50 @@ static int mpam_resctrl_pick_domain_id(int cpu, struct mpam_component *comp)
 	return comp->comp_id;
 }
 
+static void mpam_resctrl_monitor_init(struct mpam_resctrl_mon *mon,
+				      enum resctrl_event_id type)
+{
+	struct mpam_resctrl_res *res = &mpam_resctrl_controls[RDT_RESOURCE_L3];
+	struct rdt_resource *l3 = &res->resctrl_res;
+
+	lockdep_assert_cpus_held();
+
+	/* There also needs to be an L3 cache present */
+	if (get_cpu_cacheinfo_id(smp_processor_id(), 3) == -1)
+		return;
+
+	/*
+	 * If there are no MPAM resources on L3, force it into existence.
+	 * topology_matches_l3() already ensures this looks like the L3.
+	 * The domain-ids will be fixed up by mpam_resctrl_domain_hdr_init().
+	 */
+	if (!res->class) {
+		pr_warn_once("Faking L3 MSC to enable counters.\n");
+		res->class = mpam_resctrl_counters[type].class;
+	}
+
+	/* Called multiple times!, once per event type */
+	if (exposed_mon_capable) {
+		l3->mon_capable = true;
+
+		/* Setting name is necessary on monitor only platforms */
+		l3->name = "L3";
+		l3->mon_scope = RESCTRL_L3_CACHE;
+
+		resctrl_enable_mon_event(type);
+
+		/*
+		 * Unfortunately, num_rmid doesn't mean anything for
+		 * mpam, and its exposed to user-space!
+		 * num-rmid is supposed to mean the number of groups
+		 * that can be created, both control or monitor groups.
+		 * For mpam, each control group has its own pmg/rmid
+		 * space.
+		 */
+		l3->mon.num_rmid = 1;
+	}
+}
+
 u32 resctrl_arch_get_config(struct rdt_resource *r, struct rdt_ctrl_domain *d,
 			    u32 closid, enum resctrl_conf_type type)
 {
@@ -977,6 +1111,20 @@ int mpam_resctrl_setup(void)
 			break;
 		}
 	}
+
+	/* Find some classes to use for monitors */
+	mpam_resctrl_pick_counters();
+
+	for (enum resctrl_event_id j = 0; j < QOS_NUM_EVENTS; j++) {
+		struct mpam_resctrl_mon *mon;
+
+		mon = &mpam_resctrl_counters[j];
+		if (!mon->class)
+			continue;	// dummy resource
+
+		mpam_resctrl_monitor_init(mon, j);
+	}
+
 	cpus_read_unlock();
 
 	if (err) {
-- 
2.43.0

Re: [PATCH v2 27/45] arm_mpam: resctrl: Add support for csu counters

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:29 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> resctrl exposes a counter via a file named llc_occupancy. This isn't really
> a counter as its value goes up and down, this is a snapshot of the cache
> storage usage monitor.
> 
> Add some picking code to find a cache as close as possible to the L3 that
> supports the CSU monitor.
> 
> If there is an L3, but it doesn't have any controls, force the L3 resource
> to exist. The existing topology_matches_l3() and
> mpam_resctrl_domain_hdr_init() code will ensure this looks like the L3,
> even if the class belongs to a later cache.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

[PATCH v2 28/45] arm_mpam: resctrl: Pick classes for use as mbm counters

[Ben Horgan]

From: James Morse <james.morse@arm.com>

resctrl has two types of counters, NUMA-local and global. MPAM has only
bandwidth counters, but the position of the MSC may mean it counts
NUMA-local, or global traffic.

But the topology information is not available.

Apply a heuristic: the L2 or L3 supports bandwidth monitors, these are
probably NUMA-local. If the memory controller supports bandwidth monitors,
they are probably global.

This also allows us to assert that we don't have the same class backing two
different resctrl events.

Because the class or component backing the event may not be 'the L3', it is
necessary for mpam_resctrl_get_domain_from_cpu() to search the monitor
domains too. This matters the most for 'monitor only' systems, where 'the
L3' control domains may be empty, and the ctrl_comp pointer NULL.

resctrl expects there to be enough monitors for every possible control and
monitor group to have one. Such a system gets called 'free running' as the
monitors can be programmed once and left running.  Any other platform will
need to emulate ABMC.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Changes since rfc:
drop has_mbwu
---
 drivers/resctrl/mpam_internal.h |   8 ++
 drivers/resctrl/mpam_resctrl.c  | 136 +++++++++++++++++++++++++++++++-
 2 files changed, 142 insertions(+), 2 deletions(-)

diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index 9cb9eb97893b..6a2231b28cad 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -336,6 +336,14 @@ struct mpam_msc_ris {
 
 struct mpam_resctrl_dom {
 	struct mpam_component	*ctrl_comp;
+
+	/*
+	 * There is no single mon_comp because different events may be backed
+	 * by different class/components. mon_comp is indexed by the event
+	 * number.
+	 */
+	struct mpam_component   *mon_comp[QOS_NUM_EVENTS];
+
 	struct rdt_ctrl_domain	resctrl_ctrl_dom;
 	struct rdt_mon_domain	resctrl_mon_dom;
 };
diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 5fde610cc9d7..51caf3b82392 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -50,6 +50,14 @@ static bool exposed_mon_capable;
  */
 static bool cdp_enabled;
 
+/* Whether this num_mbw_mon could result in a free_running system */
+static int __mpam_monitors_free_running(u16 num_mbwu_mon)
+{
+	if (num_mbwu_mon >= resctrl_arch_system_num_rmid_idx())
+		return resctrl_arch_system_num_rmid_idx();
+	return 0;
+}
+
 bool resctrl_arch_alloc_capable(void)
 {
 	return exposed_alloc_capable;
@@ -290,6 +298,26 @@ static bool cache_has_usable_csu(struct mpam_class *class)
 	return true;
 }
 
+static bool class_has_usable_mbwu(struct mpam_class *class)
+{
+	struct mpam_props *cprops = &class->props;
+
+	if (!mpam_has_feature(mpam_feat_msmon_mbwu, cprops))
+		return false;
+
+	/*
+	 * resctrl expects the bandwidth counters to be free running,
+	 * which means we need as many monitors as resctrl has
+	 * control/monitor groups.
+	 */
+	if (__mpam_monitors_free_running(cprops->num_mbwu_mon)) {
+		pr_debug("monitors usable in free-running mode\n");
+		return true;
+	}
+
+	return false;
+}
+
 /*
  * Calculate the worst-case percentage change from each implemented step
  * in the control.
@@ -585,7 +613,36 @@ static void mpam_resctrl_pick_counters(void)
 				return;
 			}
 		}
+
+		if (class_has_usable_mbwu(class) && topology_matches_l3(class)) {
+			pr_debug("class %u has usable MBWU, and matches L3 topology",
+				 class->level);
+
+			/*
+			 * MBWU counters may be 'local' or 'total' depending on
+			 * where they are in the topology. Counters on caches
+			 * are assumed to be local. If it's on the memory
+			 * controller, its assumed to be global.
+			 */
+			switch (class->type) {
+			case MPAM_CLASS_CACHE:
+				counter_update_class(QOS_L3_MBM_LOCAL_EVENT_ID,
+						     class);
+				break;
+			case MPAM_CLASS_MEMORY:
+				counter_update_class(QOS_L3_MBM_TOTAL_EVENT_ID,
+						     class);
+				break;
+			default:
+				break;
+			}
+		}
 	}
+
+	/* Allocation of MBWU monitors assumes that the class is unique... */
+	if (mpam_resctrl_counters[QOS_L3_MBM_LOCAL_EVENT_ID].class)
+		WARN_ON_ONCE(mpam_resctrl_counters[QOS_L3_MBM_LOCAL_EVENT_ID].class ==
+			     mpam_resctrl_counters[QOS_L3_MBM_TOTAL_EVENT_ID].class);
 }
 
 static int mpam_resctrl_control_init(struct mpam_resctrl_res *res,
@@ -925,6 +982,20 @@ static void mpam_resctrl_domain_insert(struct list_head *list,
 	list_add_tail_rcu(&new->list, pos);
 }
 
+static struct mpam_component *find_component(struct mpam_class *victim, int cpu)
+{
+	struct mpam_component *victim_comp;
+
+	guard(srcu)(&mpam_srcu);
+	list_for_each_entry_srcu(victim_comp, &victim->components, class_list,
+				 srcu_read_lock_held(&mpam_srcu)) {
+		if (cpumask_test_cpu(cpu, &victim_comp->affinity))
+			return victim_comp;
+	}
+
+	return NULL;
+}
+
 static struct mpam_resctrl_dom *
 mpam_resctrl_alloc_domain(unsigned int cpu, struct mpam_resctrl_res *res)
 {
@@ -973,8 +1044,32 @@ mpam_resctrl_alloc_domain(unsigned int cpu, struct mpam_resctrl_res *res)
 	}
 
 	if (exposed_mon_capable) {
+		int i;
+		struct mpam_component *mon_comp, *any_mon_comp;
+
+		/*
+		 * Even if the monitor domain is backed by a different
+		 * component, the L3 component IDs need to be used... only
+		 * there may be no ctrl_comp for the L3.
+		 * Search each event's class list for a component with
+		 * overlapping CPUs and set up the dom->mon_comp array.
+		 */
+		for (i = 0; i < QOS_NUM_EVENTS; i++) {
+			struct mpam_resctrl_mon *mon;
+
+			mon = &mpam_resctrl_counters[i];
+			if (!mon->class)
+				continue;       // dummy resource
+
+			mon_comp = find_component(mon->class, cpu);
+			dom->mon_comp[i] = mon_comp;
+			if (mon_comp)
+				any_mon_comp = mon_comp;
+		}
+		WARN_ON_ONCE(!any_mon_comp);
+
 		mon_d = &dom->resctrl_mon_dom;
-		mpam_resctrl_domain_hdr_init(cpu, ctrl_comp, &mon_d->hdr);
+		mpam_resctrl_domain_hdr_init(cpu, any_mon_comp, &mon_d->hdr);
 		mon_d->hdr.type = RESCTRL_MON_DOMAIN;
 		mpam_resctrl_domain_insert(&r->mon_domains, &mon_d->hdr);
 		err = resctrl_online_mon_domain(r, mon_d);
@@ -996,6 +1091,39 @@ mpam_resctrl_alloc_domain(unsigned int cpu, struct mpam_resctrl_res *res)
 	return dom;
 }
 
+/*
+ * We know all the monitors are associated with the L3, even if there are no
+ * controls and therefore no control component. Find the cache-id for the CPU
+ * and use that to search for existing resctrl domains.
+ * This relies on mpam_resctrl_pick_domain_id() using the L3 cache-id
+ * for anything that is not a cache.
+ */
+static struct mpam_resctrl_dom *mpam_resctrl_get_mon_domain_from_cpu(int cpu)
+{
+	u32 cache_id;
+	struct rdt_mon_domain *mon_d;
+	struct mpam_resctrl_dom *dom;
+	struct mpam_resctrl_res *l3 = &mpam_resctrl_controls[RDT_RESOURCE_L3];
+
+	lockdep_assert_cpus_held();
+
+	if (!l3->class)
+		return NULL;
+	/* TODO: how does this order with cacheinfo updates under cpuhp? */
+	cache_id = get_cpu_cacheinfo_id(cpu, 3);
+	if (cache_id == ~0)
+		return NULL;
+
+	list_for_each_entry_rcu(mon_d, &l3->resctrl_res.mon_domains, hdr.list) {
+		dom = container_of(mon_d, struct mpam_resctrl_dom, resctrl_mon_dom);
+
+		if (mon_d->hdr.id == cache_id)
+			return dom;
+	}
+
+	return NULL;
+}
+
 static struct mpam_resctrl_dom *
 mpam_resctrl_get_domain_from_cpu(int cpu, struct mpam_resctrl_res *res)
 {
@@ -1013,7 +1141,11 @@ mpam_resctrl_get_domain_from_cpu(int cpu, struct mpam_resctrl_res *res)
 			return dom;
 	}
 
-	return NULL;
+	if (r->rid != RDT_RESOURCE_L3)
+		return NULL;
+
+	/* Search the mon domain list too - needed on monitor only platforms. */
+	return mpam_resctrl_get_mon_domain_from_cpu(cpu);
 }
 
 int mpam_resctrl_online_cpu(unsigned int cpu)
-- 
2.43.0

Re: [PATCH v2 28/45] arm_mpam: resctrl: Pick classes for use as mbm counters

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:30 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> resctrl has two types of counters, NUMA-local and global. MPAM has only
> bandwidth counters, but the position of the MSC may mean it counts
> NUMA-local, or global traffic.
> 
> But the topology information is not available.
> 
> Apply a heuristic: the L2 or L3 supports bandwidth monitors, these are
> probably NUMA-local. If the memory controller supports bandwidth monitors,
> they are probably global.
> 
> This also allows us to assert that we don't have the same class backing two
> different resctrl events.
> 
> Because the class or component backing the event may not be 'the L3', it is
> necessary for mpam_resctrl_get_domain_from_cpu() to search the monitor
> domains too. This matters the most for 'monitor only' systems, where 'the
> L3' control domains may be empty, and the ctrl_comp pointer NULL.
> 
> resctrl expects there to be enough monitors for every possible control and
> monitor group to have one. Such a system gets called 'free running' as the
> monitors can be programmed once and left running.  Any other platform will
> need to emulate ABMC.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Hi Ben,

A few minor comments inline. + one question on a worrying sounding todo.

Jonathan

> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> index 5fde610cc9d7..51caf3b82392 100644
> --- a/drivers/resctrl/mpam_resctrl.c
> +++ b/drivers/resctrl/mpam_resctrl.c



> @@ -925,6 +982,20 @@ static void mpam_resctrl_domain_insert(struct list_head *list,
>  	list_add_tail_rcu(&new->list, pos);
>  }
>  
> +static struct mpam_component *find_component(struct mpam_class *victim, int cpu)

This is a lovely generic sounding thing, but then the term victim comes in which
is very usecase specific.  Maybe something could have a better name? (either
function or avoid the victim naming).

> +{
> +	struct mpam_component *victim_comp;
> +
> +	guard(srcu)(&mpam_srcu);
> +	list_for_each_entry_srcu(victim_comp, &victim->components, class_list,
> +				 srcu_read_lock_held(&mpam_srcu)) {
> +		if (cpumask_test_cpu(cpu, &victim_comp->affinity))
> +			return victim_comp;
> +	}
> +
> +	return NULL;
> +}
> +
>  static struct mpam_resctrl_dom *
>  mpam_resctrl_alloc_domain(unsigned int cpu, struct mpam_resctrl_res *res)
>  {
> @@ -973,8 +1044,32 @@ mpam_resctrl_alloc_domain(unsigned int cpu, struct mpam_resctrl_res *res)
>  	}
>  
>  	if (exposed_mon_capable) {
> +		int i;
> +		struct mpam_component *mon_comp, *any_mon_comp;
> +
> +		/*
> +		 * Even if the monitor domain is backed by a different
> +		 * component, the L3 component IDs need to be used... only
> +		 * there may be no ctrl_comp for the L3.
> +		 * Search each event's class list for a component with
> +		 * overlapping CPUs and set up the dom->mon_comp array.
> +		 */
> +		for (i = 0; i < QOS_NUM_EVENTS; i++) {
For consistency with other loops (some of them anyway, I've not done
a detailed survey ;) I'd do
		for (int i = 0; ...
Probably bring scope of the mon_comp in here too.


> +			struct mpam_resctrl_mon *mon;
> +
> +			mon = &mpam_resctrl_counters[i];
> +			if (!mon->class)
> +				continue;       // dummy resource
> +
> +			mon_comp = find_component(mon->class, cpu);
> +			dom->mon_comp[i] = mon_comp;
> +			if (mon_comp)
> +				any_mon_comp = mon_comp;
> +		}
> +		WARN_ON_ONCE(!any_mon_comp);
> +
>  		mon_d = &dom->resctrl_mon_dom;
> -		mpam_resctrl_domain_hdr_init(cpu, ctrl_comp, &mon_d->hdr);
> +		mpam_resctrl_domain_hdr_init(cpu, any_mon_comp, &mon_d->hdr);
>  		mon_d->hdr.type = RESCTRL_MON_DOMAIN;
>  		mpam_resctrl_domain_insert(&r->mon_domains, &mon_d->hdr);
>  		err = resctrl_online_mon_domain(r, mon_d);
> @@ -996,6 +1091,39 @@ mpam_resctrl_alloc_domain(unsigned int cpu, struct mpam_resctrl_res *res)
>  	return dom;
>  }
>  
> +/*
> + * We know all the monitors are associated with the L3, even if there are no
> + * controls and therefore no control component. Find the cache-id for the CPU
> + * and use that to search for existing resctrl domains.
> + * This relies on mpam_resctrl_pick_domain_id() using the L3 cache-id
> + * for anything that is not a cache.
> + */
> +static struct mpam_resctrl_dom *mpam_resctrl_get_mon_domain_from_cpu(int cpu)
> +{
> +	u32 cache_id;
> +	struct rdt_mon_domain *mon_d;
> +	struct mpam_resctrl_dom *dom;
> +	struct mpam_resctrl_res *l3 = &mpam_resctrl_controls[RDT_RESOURCE_L3];
> +
> +	lockdep_assert_cpus_held();
> +
> +	if (!l3->class)
> +		return NULL;
> +	/* TODO: how does this order with cacheinfo updates under cpuhp? */

Considered a blocking todo or something that is future work to resolve if there
is an issue?

> +	cache_id = get_cpu_cacheinfo_id(cpu, 3);
> +	if (cache_id == ~0)
> +		return NULL;
> +
> +	list_for_each_entry_rcu(mon_d, &l3->resctrl_res.mon_domains, hdr.list) {
> +		dom = container_of(mon_d, struct mpam_resctrl_dom, resctrl_mon_dom);
Might as well move this under the condition.
I'm assuming no later patch needs dom for other reasons.

		if (mon_d->hdr.id == cache_id)
			return container_of(mon_d, struct mpam_resctrl_dom, resctrl_mon_dom);

> +
> +		if (mon_d->hdr.id == cache_id)
> +			return dom;
> +	}
> +
> +	return NULL;
> +}

Re: [PATCH v2 28/45] arm_mpam: resctrl: Pick classes for use as mbm counters

[Ben Horgan]

Hi Jonathan,

On 1/6/26 14:01, Jonathan Cameron wrote:
> On Fri, 19 Dec 2025 18:11:30 +0000
> Ben Horgan <ben.horgan@arm.com> wrote:
> 
>> From: James Morse <james.morse@arm.com>
>>
>> resctrl has two types of counters, NUMA-local and global. MPAM has only
>> bandwidth counters, but the position of the MSC may mean it counts
>> NUMA-local, or global traffic.
>>
>> But the topology information is not available.
>>
>> Apply a heuristic: the L2 or L3 supports bandwidth monitors, these are
>> probably NUMA-local. If the memory controller supports bandwidth monitors,
>> they are probably global.
>>
>> This also allows us to assert that we don't have the same class backing two
>> different resctrl events.
>>
>> Because the class or component backing the event may not be 'the L3', it is
>> necessary for mpam_resctrl_get_domain_from_cpu() to search the monitor
>> domains too. This matters the most for 'monitor only' systems, where 'the
>> L3' control domains may be empty, and the ctrl_comp pointer NULL.
>>
>> resctrl expects there to be enough monitors for every possible control and
>> monitor group to have one. Such a system gets called 'free running' as the
>> monitors can be programmed once and left running.  Any other platform will
>> need to emulate ABMC.
>>
>> Signed-off-by: James Morse <james.morse@arm.com>
>> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> Hi Ben,
> 
> A few minor comments inline. + one question on a worrying sounding todo.
> 
> Jonathan
> 
>> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
>> index 5fde610cc9d7..51caf3b82392 100644
>> --- a/drivers/resctrl/mpam_resctrl.c
>> +++ b/drivers/resctrl/mpam_resctrl.c
> 
> 
> 
>> @@ -925,6 +982,20 @@ static void mpam_resctrl_domain_insert(struct list_head *list,
>>  	list_add_tail_rcu(&new->list, pos);
>>  }
>>  
>> +static struct mpam_component *find_component(struct mpam_class *victim, int cpu)
> 
> This is a lovely generic sounding thing, but then the term victim comes in which
> is very usecase specific.  Maybe something could have a better name? (either
> function or avoid the victim naming).

I'll keep it friendly and drop the victim naming.

> 
>> +{
>> +	struct mpam_component *victim_comp;
>> +
>> +	guard(srcu)(&mpam_srcu);
>> +	list_for_each_entry_srcu(victim_comp, &victim->components, class_list,
>> +				 srcu_read_lock_held(&mpam_srcu)) {
>> +		if (cpumask_test_cpu(cpu, &victim_comp->affinity))
>> +			return victim_comp;
>> +	}
>> +
>> +	return NULL;
>> +}
>> +
>>  static struct mpam_resctrl_dom *
>>  mpam_resctrl_alloc_domain(unsigned int cpu, struct mpam_resctrl_res *res)
>>  {
>> @@ -973,8 +1044,32 @@ mpam_resctrl_alloc_domain(unsigned int cpu, struct mpam_resctrl_res *res)
>>  	}
>>  
>>  	if (exposed_mon_capable) {
>> +		int i;
>> +		struct mpam_component *mon_comp, *any_mon_comp;
>> +
>> +		/*
>> +		 * Even if the monitor domain is backed by a different
>> +		 * component, the L3 component IDs need to be used... only
>> +		 * there may be no ctrl_comp for the L3.
>> +		 * Search each event's class list for a component with
>> +		 * overlapping CPUs and set up the dom->mon_comp array.
>> +		 */
>> +		for (i = 0; i < QOS_NUM_EVENTS; i++) {
> For consistency with other loops (some of them anyway, I've not done
> a detailed survey ;) I'd do
> 		for (int i = 0; ...
> Probably bring scope of the mon_comp in here too.

Done.

> 
> 
>> +			struct mpam_resctrl_mon *mon;
>> +
>> +			mon = &mpam_resctrl_counters[i];
>> +			if (!mon->class)
>> +				continue;       // dummy resource
>> +
>> +			mon_comp = find_component(mon->class, cpu);
>> +			dom->mon_comp[i] = mon_comp;
>> +			if (mon_comp)
>> +				any_mon_comp = mon_comp;
>> +		}
>> +		WARN_ON_ONCE(!any_mon_comp);
>> +
>>  		mon_d = &dom->resctrl_mon_dom;
>> -		mpam_resctrl_domain_hdr_init(cpu, ctrl_comp, &mon_d->hdr);
>> +		mpam_resctrl_domain_hdr_init(cpu, any_mon_comp, &mon_d->hdr);
>>  		mon_d->hdr.type = RESCTRL_MON_DOMAIN;
>>  		mpam_resctrl_domain_insert(&r->mon_domains, &mon_d->hdr);
>>  		err = resctrl_online_mon_domain(r, mon_d);
>> @@ -996,6 +1091,39 @@ mpam_resctrl_alloc_domain(unsigned int cpu, struct mpam_resctrl_res *res)
>>  	return dom;
>>  }
>>  
>> +/*
>> + * We know all the monitors are associated with the L3, even if there are no
>> + * controls and therefore no control component. Find the cache-id for the CPU
>> + * and use that to search for existing resctrl domains.
>> + * This relies on mpam_resctrl_pick_domain_id() using the L3 cache-id
>> + * for anything that is not a cache.
>> + */
>> +static struct mpam_resctrl_dom *mpam_resctrl_get_mon_domain_from_cpu(int cpu)
>> +{
>> +	u32 cache_id;
>> +	struct rdt_mon_domain *mon_d;
>> +	struct mpam_resctrl_dom *dom;
>> +	struct mpam_resctrl_res *l3 = &mpam_resctrl_controls[RDT_RESOURCE_L3];
>> +
>> +	lockdep_assert_cpus_held();
>> +
>> +	if (!l3->class)
>> +		return NULL;
>> +	/* TODO: how does this order with cacheinfo updates under cpuhp? */
> 
> Considered a blocking todo or something that is future work to resolve if there
> is an issue?

This is synchronized by the wait_event() in mpam_resctrl_setup() but I
realize now that this is only added later in the series. I'll consider
bringing that earlier in the series.

> 
>> +	cache_id = get_cpu_cacheinfo_id(cpu, 3);
>> +	if (cache_id == ~0)
>> +		return NULL;
>> +
>> +	list_for_each_entry_rcu(mon_d, &l3->resctrl_res.mon_domains, hdr.list) {
>> +		dom = container_of(mon_d, struct mpam_resctrl_dom, resctrl_mon_dom);
> Might as well move this under the condition.
> I'm assuming no later patch needs dom for other reasons.
> 
> 		if (mon_d->hdr.id == cache_id)
> 			return container_of(mon_d, struct mpam_resctrl_dom, resctrl_mon_dom);

I've updated to this already based on your comments on the rfc.

> 
>> +
>> +		if (mon_d->hdr.id == cache_id)
>> +			return dom;
>> +	}
>> +
>> +	return NULL;
>> +}

Thanks,

Ben

[PATCH v2 29/45] arm_mpam: resctrl: Pre-allocate free running monitors

[Ben Horgan]

From: James Morse <james.morse@arm.com>

When there are enough monitors, the resctrl mbm local and total files can
be exposed. These need all the monitors that resctrl may use to be
allocated up front.

Add helpers to do this.

If a different candidate class is discovered, the old array should be
free'd and the allocated monitors returned to the driver.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 drivers/resctrl/mpam_internal.h |  8 +++-
 drivers/resctrl/mpam_resctrl.c  | 84 ++++++++++++++++++++++++++++++++-
 2 files changed, 89 insertions(+), 3 deletions(-)

diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index 6a2231b28cad..c25524f75c2e 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -356,7 +356,13 @@ struct mpam_resctrl_res {
 struct mpam_resctrl_mon {
 	struct mpam_class	*class;
 
-	/* per-class data that resctrl needs will live here */
+	/*
+	 * Array of allocated MBWU monitors, indexed by (closid, rmid).
+	 * When ABMC is not in use, this array directly maps (closid, rmid)
+	 * to the allocated monitor. Otherwise this array is sparse, and
+	 * un-assigned (closid, rmid) are -1.
+	 */
+	int			*mbwu_idx_to_mon;
 };
 
 static inline int mpam_alloc_csu_mon(struct mpam_class *class)
diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 51caf3b82392..bea16bc096f7 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -558,10 +558,58 @@ static void mpam_resctrl_pick_mba(void)
 	}
 }
 
+static void __free_mbwu_mon(struct mpam_class *class, int *array,
+			    u16 num_mbwu_mon)
+{
+	for (int i = 0; i < num_mbwu_mon; i++) {
+		if (array[i] < 0)
+			continue;
+
+		mpam_free_mbwu_mon(class, array[i]);
+		array[i] = ~0;
+	}
+}
+
+static int __alloc_mbwu_mon(struct mpam_class *class, int *array,
+			    u16 num_mbwu_mon)
+{
+	for (int i = 0; i < num_mbwu_mon; i++) {
+		int mbwu_mon = mpam_alloc_mbwu_mon(class);
+
+		if (mbwu_mon < 0) {
+			__free_mbwu_mon(class, array, num_mbwu_mon);
+			return mbwu_mon;
+		}
+		array[i] = mbwu_mon;
+	}
+
+	return 0;
+}
+
+static int *__alloc_mbwu_array(struct mpam_class *class, u16 num_mbwu_mon)
+{
+	int err;
+	size_t array_size = num_mbwu_mon * sizeof(int);
+	int *array __free(kfree) = kmalloc(array_size, GFP_KERNEL);
+
+	if (!array)
+		return ERR_PTR(-ENOMEM);
+
+	memset(array, -1, array_size);
+
+	err = __alloc_mbwu_mon(class, array, num_mbwu_mon);
+	if (err)
+		return ERR_PTR(err);
+	return_ptr(array);
+}
+
 static void counter_update_class(enum resctrl_event_id evt_id,
 				 struct mpam_class *class)
 {
-	struct mpam_class *existing_class = mpam_resctrl_counters[evt_id].class;
+	struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[evt_id];
+	struct mpam_class *existing_class = mon->class;
+	u16 num_mbwu_mon = class->props.num_mbwu_mon;
+	int *existing_array = mon->mbwu_idx_to_mon;
 
 	if (existing_class) {
 		if (class->level == 3) {
@@ -576,8 +624,40 @@ static void counter_update_class(enum resctrl_event_id evt_id,
 		}
 	}
 
-	mpam_resctrl_counters[evt_id].class = class;
+	pr_debug("Updating event %u to use class %u\n", evt_id, class->level);
+	mon->class = class;
 	exposed_mon_capable = true;
+
+	if (evt_id == QOS_L3_OCCUP_EVENT_ID)
+		return;
+
+	/* Might not need all the monitors */
+	num_mbwu_mon = __mpam_monitors_free_running(num_mbwu_mon);
+	if (!num_mbwu_mon) {
+		pr_debug("Not pre-allocating free-running counters\n");
+		return;
+	}
+
+	/*
+	 * This is the pre-allocated free-running monitors path. It always
+	 * allocates one monitor per PARTID * PMG.
+	 */
+	WARN_ON_ONCE(num_mbwu_mon != resctrl_arch_system_num_rmid_idx());
+
+	mon->mbwu_idx_to_mon = __alloc_mbwu_array(class, num_mbwu_mon);
+	if (IS_ERR(mon->mbwu_idx_to_mon)) {
+		pr_debug("Failed to allocate MBWU array\n");
+		mon->class = existing_class;
+		mon->mbwu_idx_to_mon = existing_array;
+		return;
+	}
+
+	if (existing_array) {
+		pr_debug("Releasing previous class %u's monitors\n",
+			 existing_class->level);
+		__free_mbwu_mon(existing_class, existing_array, num_mbwu_mon);
+		kfree(existing_array);
+	}
 }
 
 static void mpam_resctrl_pick_counters(void)
-- 
2.43.0

Re: [PATCH v2 29/45] arm_mpam: resctrl: Pre-allocate free running monitors

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:31 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> When there are enough monitors, the resctrl mbm local and total files can
> be exposed. These need all the monitors that resctrl may use to be
> allocated up front.
> 
> Add helpers to do this.
> 
> If a different candidate class is discovered, the old array should be
> free'd and the allocated monitors returned to the driver.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>

See below.  Maybe there isn't a nicer way to handle the error
cases in counter_update_class() but I think it can be improved at least
a little.

> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> index 51caf3b82392..bea16bc096f7 100644
> --- a/drivers/resctrl/mpam_resctrl.c
> +++ b/drivers/resctrl/mpam_resctrl.c

> +
>  static void counter_update_class(enum resctrl_event_id evt_id,
>  				 struct mpam_class *class)
The stuff below is very much a case of me trying to figure out a nicer
code flow in here and stumbling a bit over what it can be, however
I do think this function would benefit from another look.

>  {
> -	struct mpam_class *existing_class = mpam_resctrl_counters[evt_id].class;
> +	struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[evt_id];
> +	struct mpam_class *existing_class = mon->class;
> +	u16 num_mbwu_mon = class->props.num_mbwu_mon;
> +	int *existing_array = mon->mbwu_idx_to_mon;
>  
>  	if (existing_class) {
>  		if (class->level == 3) {
> @@ -576,8 +624,40 @@ static void counter_update_class(enum resctrl_event_id evt_id,
>  		}
>  	}
>  
> -	mpam_resctrl_counters[evt_id].class = class;
> +	pr_debug("Updating event %u to use class %u\n", evt_id, class->level);
> +	mon->class = class;
>  	exposed_mon_capable = true;
> +
> +	if (evt_id == QOS_L3_OCCUP_EVENT_ID)
> +		return;
> +
> +	/* Might not need all the monitors */
> +	num_mbwu_mon = __mpam_monitors_free_running(num_mbwu_mon);
> +	if (!num_mbwu_mon) {

For the below suggestion would need duplicate setting 
		mon->class = class;
here (which is the one disadvantage I can see in setting it later than
currently.  One option would be to flip the logic here and
not exit early, allowing sharing of that statement after the
rest of the code.
	if (num_mbw_mon) {
		stuff to allocate array.
	} else {
		pr_debug("Not pre-allocating...);
	}
	mon->class = class;
}



> +		pr_debug("Not pre-allocating free-running counters\n");
> +		return;
> +	}
> +
> +	/*
> +	 * This is the pre-allocated free-running monitors path. It always
> +	 * allocates one monitor per PARTID * PMG.
> +	 */
> +	WARN_ON_ONCE(num_mbwu_mon != resctrl_arch_system_num_rmid_idx());
> +
> +	mon->mbwu_idx_to_mon = __alloc_mbwu_array(class, num_mbwu_mon);

This might be cleaner with a local so as to avoid setting and reverting on error.
Also, does anything stop mon->class being set after this?
Seems like that would be cleaner.

	int *new_array; // up top obviously.

	new_array = __alloc_mbwu_array(class, num_mbwu_mon);
	if (IS_ERR(new_array)) {
		pr_debug("Failed to allocate MBWU array\n");
		return;
	}

//this bit less obviously a good idea.
	if (mon->mbwu_idx_to_mon) {
		pr_debug("Releasing previous class %u's monitors\n",
			 mon->mbwu_idx_to_mon->level);
		__free_mbwu_mon(mon->class, mon->mbwu_idx_to_mon, num_mbwu_mon);
		kfree(mon->mbwu_idx_to_mon);
	}
//so maybe skip that bit.
//Anyhow aim is to set these only after we know we are good carry on.
	mon->mbwu_idx_to_mon = new_array;
	mon->class = class;


Some parts of this might make sense without going the whole way. Maybe
just setting the array late and leaving the class set early then
reverting that on error.


> +	if (IS_ERR(mon->mbwu_idx_to_mon)) {
> +		pr_debug("Failed to allocate MBWU array\n");
> +		mon->class = existing_class;
> +		mon->mbwu_idx_to_mon = existing_array;
> +		return;
> +	}
> +
> +	if (existing_array) {
> +		pr_debug("Releasing previous class %u's monitors\n",
> +			 existing_class->level);
> +		__free_mbwu_mon(existing_class, existing_array, num_mbwu_mon);
> +		kfree(existing_array);
> +	}
>  }
>  
>  static void mpam_resctrl_pick_counters(void)

[PATCH v2 30/45] arm_mpam: resctrl: Pre-allocate assignable monitors

[Ben Horgan]

From: James Morse <james.morse@arm.com>

When there are not enough monitors, MPAM is able to emulate ABMC by making
a smaller number of monitors assignable. These monitors still need to be
allocated from the driver, and mapped to whichever control/monitor group
resctrl wants to use them with.

Add a second array to hold the monitor values indexed by resctrl's cntr_id.

When CDP is in use, two monitors are needed so the available number of
counters halves. Platforms with one monitor will have zero monitors when
CDP is in use.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Changes since rfc:
Move __free
kmalloc -> kcalloc
---
 drivers/resctrl/mpam_internal.h |   7 +++
 drivers/resctrl/mpam_resctrl.c  | 103 ++++++++++++++++++++++++++++++++
 2 files changed, 110 insertions(+)

diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index c25524f75c2e..a2f6956d9236 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -363,6 +363,13 @@ struct mpam_resctrl_mon {
 	 * un-assigned (closid, rmid) are -1.
 	 */
 	int			*mbwu_idx_to_mon;
+
+	/*
+	 * Array of assigned MBWU monitors, indexed by idx argument.
+	 * When ABMC is not in use, this array can be NULL. Otherwise
+	 * it maps idx to the allocated monitor.
+	 */
+	int			*assigned_counters;
 };
 
 static inline int mpam_alloc_csu_mon(struct mpam_class *class)
diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index bea16bc096f7..e96d320c219c 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -50,6 +50,12 @@ static bool exposed_mon_capable;
  */
 static bool cdp_enabled;
 
+/*
+ * L3 local/total may come from different classes - what is the number of MBWU
+ * 'on L3'?
+ */
+static unsigned int l3_num_allocated_mbwu = ~0;
+
 /* Whether this num_mbw_mon could result in a free_running system */
 static int __mpam_monitors_free_running(u16 num_mbwu_mon)
 {
@@ -58,6 +64,15 @@ static int __mpam_monitors_free_running(u16 num_mbwu_mon)
 	return 0;
 }
 
+/*
+ * If l3_num_allocated_mbwu is forced below PARTID * PMG, then the counters
+ * are not free running, and ABMC's user-interface must be used to assign them.
+ */
+static bool mpam_resctrl_abmc_enabled(void)
+{
+	return l3_num_allocated_mbwu < resctrl_arch_system_num_rmid_idx();
+}
+
 bool resctrl_arch_alloc_capable(void)
 {
 	return exposed_alloc_capable;
@@ -102,9 +117,26 @@ static void resctrl_reset_task_closids(void)
 	read_unlock(&tasklist_lock);
 }
 
+static void mpam_resctrl_monitor_sync_abmc_vals(struct rdt_resource *l3)
+{
+	l3->mon.num_mbm_cntrs = l3_num_allocated_mbwu;
+	if (cdp_enabled)
+		l3->mon.num_mbm_cntrs /= 2;
+
+	if (l3->mon.num_mbm_cntrs) {
+		l3->mon.mbm_cntr_assignable = mpam_resctrl_abmc_enabled();
+		l3->mon.mbm_assign_on_mkdir = mpam_resctrl_abmc_enabled();
+	} else {
+		l3->mon.mbm_cntr_assignable = false;
+		l3->mon.mbm_assign_on_mkdir = false;
+	}
+}
+
 int resctrl_arch_set_cdp_enabled(enum resctrl_res_level ignored, bool enable)
 {
 	u32 partid_i = RESCTRL_RESERVED_CLOSID, partid_d = RESCTRL_RESERVED_CLOSID;
+	struct mpam_resctrl_res *res = &mpam_resctrl_controls[RDT_RESOURCE_L3];
+	struct rdt_resource *l3 = &res->resctrl_res;
 
 	cdp_enabled = enable;
 
@@ -120,6 +152,7 @@ int resctrl_arch_set_cdp_enabled(enum resctrl_res_level ignored, bool enable)
 	WRITE_ONCE(arm64_mpam_global_default, mpam_get_regval(current));
 
 	resctrl_reset_task_closids();
+	mpam_resctrl_monitor_sync_abmc_vals(l3);
 
 	return 0;
 }
@@ -315,6 +348,11 @@ static bool class_has_usable_mbwu(struct mpam_class *class)
 		return true;
 	}
 
+	if (cprops->num_mbwu_mon) {
+		pr_debug("monitors usable via ABMC assignment\n");
+		return true;
+	}
+
 	return false;
 }
 
@@ -583,6 +621,8 @@ static int __alloc_mbwu_mon(struct mpam_class *class, int *array,
 		array[i] = mbwu_mon;
 	}
 
+	l3_num_allocated_mbwu = min(l3_num_allocated_mbwu, num_mbwu_mon);
+
 	return 0;
 }
 
@@ -725,6 +765,23 @@ static void mpam_resctrl_pick_counters(void)
 			     mpam_resctrl_counters[QOS_L3_MBM_TOTAL_EVENT_ID].class);
 }
 
+bool resctrl_arch_mbm_cntr_assign_enabled(struct rdt_resource *r)
+{
+	if (r != &mpam_resctrl_controls[RDT_RESOURCE_L3].resctrl_res)
+		return false;
+
+	return mpam_resctrl_abmc_enabled();
+}
+
+int resctrl_arch_mbm_cntr_assign_set(struct rdt_resource *r, bool enable)
+{
+	lockdep_assert_cpus_held();
+
+	WARN_ON_ONCE(1);
+
+	return 0;
+}
+
 static int mpam_resctrl_control_init(struct mpam_resctrl_res *res,
 				     enum resctrl_res_level type)
 {
@@ -804,6 +861,42 @@ static int mpam_resctrl_pick_domain_id(int cpu, struct mpam_component *comp)
 	return comp->comp_id;
 }
 
+/*
+ * This must run after all event counters have been picked so that any free
+ * running counters have already been allocated.
+ */
+static int mpam_resctrl_monitor_init_abmc(struct mpam_resctrl_mon *mon)
+{
+	struct mpam_resctrl_res *res = &mpam_resctrl_controls[RDT_RESOURCE_L3];
+	struct rdt_resource *l3 = &res->resctrl_res;
+	struct mpam_class *class = mon->class;
+	u16 num_mbwu_mon;
+
+	if (mon->mbwu_idx_to_mon) {
+		pr_debug("monitors free running\n");
+		return 0;
+	}
+
+	int *rmid_array __free(kfree) =
+		kcalloc(resctrl_arch_system_num_rmid_idx(), sizeof(int), GFP_KERNEL);
+
+	if (!rmid_array) {
+		pr_debug("Failed to allocate RMID array\n");
+		return -ENOMEM;
+	}
+	memset(rmid_array, -1, resctrl_arch_system_num_rmid_idx() * sizeof(int));
+
+	num_mbwu_mon = class->props.num_mbwu_mon;
+	mon->assigned_counters = __alloc_mbwu_array(mon->class, num_mbwu_mon);
+	if (IS_ERR(mon->assigned_counters))
+		return PTR_ERR(mon->assigned_counters);
+	mon->mbwu_idx_to_mon = no_free_ptr(rmid_array);
+
+	mpam_resctrl_monitor_sync_abmc_vals(l3);
+
+	return 0;
+}
+
 static void mpam_resctrl_monitor_init(struct mpam_resctrl_mon *mon,
 				      enum resctrl_event_id type)
 {
@@ -845,6 +938,16 @@ static void mpam_resctrl_monitor_init(struct mpam_resctrl_mon *mon,
 		 * space.
 		 */
 		l3->mon.num_rmid = 1;
+
+		switch (type) {
+		case QOS_L3_MBM_LOCAL_EVENT_ID:
+		case QOS_L3_MBM_TOTAL_EVENT_ID:
+			mpam_resctrl_monitor_init_abmc(mon);
+
+			return;
+		default:
+			return;
+		}
 	}
 }
 
-- 
2.43.0

Re: [PATCH v2 30/45] arm_mpam: resctrl: Pre-allocate assignable monitors

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:32 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> When there are not enough monitors, MPAM is able to emulate ABMC by making
> a smaller number of monitors assignable. These monitors still need to be
> allocated from the driver, and mapped to whichever control/monitor group
> resctrl wants to use them with.
> 
> Add a second array to hold the monitor values indexed by resctrl's cntr_id.
> 
> When CDP is in use, two monitors are needed so the available number of
> counters halves. Platforms with one monitor will have zero monitors when
> CDP is in use.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> ---
> Changes since rfc:
> Move __free
> kmalloc -> kcalloc
>  

Trivial comments only,
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

>  static inline int mpam_alloc_csu_mon(struct mpam_class *class)
> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> index bea16bc096f7..e96d320c219c 100644
> --- a/drivers/resctrl/mpam_resctrl.c
> +++ b/drivers/resctrl/mpam_resctrl.c

> +/*
> + * This must run after all event counters have been picked so that any free
> + * running counters have already been allocated.
> + */
> +static int mpam_resctrl_monitor_init_abmc(struct mpam_resctrl_mon *mon)
> +{
> +	struct mpam_resctrl_res *res = &mpam_resctrl_controls[RDT_RESOURCE_L3];
> +	struct rdt_resource *l3 = &res->resctrl_res;
> +	struct mpam_class *class = mon->class;
> +	u16 num_mbwu_mon;
> +
> +	if (mon->mbwu_idx_to_mon) {
> +		pr_debug("monitors free running\n");
> +		return 0;
> +	}
> +
> +	int *rmid_array __free(kfree) =
> +		kcalloc(resctrl_arch_system_num_rmid_idx(), sizeof(int), GFP_KERNEL);

It's a long line, but I'd prefer sizeof(*rmid_array).
could use kmalloc_array to avoid zeroing just before you fill it with -1.

> +
> +	if (!rmid_array) {
> +		pr_debug("Failed to allocate RMID array\n");
> +		return -ENOMEM;
> +	}
> +	memset(rmid_array, -1, resctrl_arch_system_num_rmid_idx() * sizeof(int));
> +
> +	num_mbwu_mon = class->props.num_mbwu_mon;
> +	mon->assigned_counters = __alloc_mbwu_array(mon->class, num_mbwu_mon);
> +	if (IS_ERR(mon->assigned_counters))
> +		return PTR_ERR(mon->assigned_counters);
> +	mon->mbwu_idx_to_mon = no_free_ptr(rmid_array);
> +
> +	mpam_resctrl_monitor_sync_abmc_vals(l3);
> +
> +	return 0;
> +}

[PATCH v2 31/45] arm_mpam: resctrl: Add kunit test for ABMC/CDP interactions

[Ben Horgan]

From: James Morse <james.morse@arm.com>

ABMC exposes a fun corner case where a platform with one monitor can use
ABMC for assignable counters - but not when CDP is enabled.

Add some tests.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 drivers/resctrl/test_mpam_resctrl.c | 62 +++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)

diff --git a/drivers/resctrl/test_mpam_resctrl.c b/drivers/resctrl/test_mpam_resctrl.c
index d0615aa7671c..c83d54f21fa0 100644
--- a/drivers/resctrl/test_mpam_resctrl.c
+++ b/drivers/resctrl/test_mpam_resctrl.c
@@ -293,6 +293,67 @@ static void test_percent_to_max_rounding(struct kunit *test)
 	KUNIT_EXPECT_LE(test, 4 * num_rounded_up, 3 * total);
 }
 
+static void test_num_assignable_counters(struct kunit *test)
+{
+	unsigned int orig_l3_num_allocated_mbwu = l3_num_allocated_mbwu;
+	u32 orig_mpam_partid_max = mpam_partid_max;
+	u32 orig_mpam_pmg_max = mpam_pmg_max;
+	bool orig_cdp_enabled = cdp_enabled;
+	struct rdt_resource fake_l3;
+
+	/* Force there to be some PARTID/PMG */
+	mpam_partid_max = 3;
+	mpam_pmg_max = 1;
+
+	cdp_enabled = false;
+
+	/* ABMC off, CDP off */
+	l3_num_allocated_mbwu = resctrl_arch_system_num_rmid_idx();
+	mpam_resctrl_monitor_sync_abmc_vals(&fake_l3);
+	KUNIT_EXPECT_EQ(test, fake_l3.mon.num_mbm_cntrs, resctrl_arch_system_num_rmid_idx());
+	KUNIT_EXPECT_FALSE(test, fake_l3.mon.mbm_cntr_assignable);
+	KUNIT_EXPECT_FALSE(test, fake_l3.mon.mbm_assign_on_mkdir);
+
+	/* ABMC on, CDP off */
+	l3_num_allocated_mbwu = 4;
+	mpam_resctrl_monitor_sync_abmc_vals(&fake_l3);
+	KUNIT_EXPECT_EQ(test, fake_l3.mon.num_mbm_cntrs, 4);
+	KUNIT_EXPECT_TRUE(test, fake_l3.mon.mbm_cntr_assignable);
+	KUNIT_EXPECT_TRUE(test, fake_l3.mon.mbm_assign_on_mkdir);
+
+	cdp_enabled = true;
+
+	/* ABMC off, CDP on */
+	l3_num_allocated_mbwu = resctrl_arch_system_num_rmid_idx();
+	mpam_resctrl_monitor_sync_abmc_vals(&fake_l3);
+
+	/* (value not consumed by resctrl) */
+	KUNIT_EXPECT_EQ(test, fake_l3.mon.num_mbm_cntrs, resctrl_arch_system_num_rmid_idx() / 2);
+
+	KUNIT_EXPECT_FALSE(test, fake_l3.mon.mbm_cntr_assignable);
+	KUNIT_EXPECT_FALSE(test, fake_l3.mon.mbm_assign_on_mkdir);
+
+	/* ABMC on, CDP on */
+	l3_num_allocated_mbwu = 4;
+	mpam_resctrl_monitor_sync_abmc_vals(&fake_l3);
+	KUNIT_EXPECT_EQ(test, fake_l3.mon.num_mbm_cntrs, 2);
+	KUNIT_EXPECT_TRUE(test, fake_l3.mon.mbm_cntr_assignable);
+	KUNIT_EXPECT_TRUE(test, fake_l3.mon.mbm_assign_on_mkdir);
+
+	/* ABMC 'on', CDP on - but not enough counters */
+	l3_num_allocated_mbwu = 1;
+	mpam_resctrl_monitor_sync_abmc_vals(&fake_l3);
+	KUNIT_EXPECT_EQ(test, fake_l3.mon.num_mbm_cntrs, 0);
+	KUNIT_EXPECT_FALSE(test, fake_l3.mon.mbm_cntr_assignable);
+	KUNIT_EXPECT_FALSE(test, fake_l3.mon.mbm_assign_on_mkdir);
+
+	/* Restore global variables that were messed with */
+	l3_num_allocated_mbwu = orig_l3_num_allocated_mbwu;
+	mpam_partid_max = orig_mpam_partid_max;
+	mpam_pmg_max = orig_mpam_pmg_max;
+	cdp_enabled = orig_cdp_enabled;
+}
+
 static struct kunit_case mpam_resctrl_test_cases[] = {
 	KUNIT_CASE(test_get_mba_granularity),
 	KUNIT_CASE_PARAM(test_mbw_max_to_percent, test_percent_value_gen_params),
@@ -301,6 +362,7 @@ static struct kunit_case mpam_resctrl_test_cases[] = {
 	KUNIT_CASE(test_percent_to_max_rounding),
 	KUNIT_CASE_PARAM(test_percent_max_roundtrip_stability,
 			 test_all_bwa_wd_gen_params),
+	KUNIT_CASE(test_num_assignable_counters),
 	{}
 };
 
-- 
2.43.0

[PATCH v2 32/45] arm_mpam: resctrl: Add resctrl_arch_config_cntr() for ABMC use

[Ben Horgan]

From: James Morse <james.morse@arm.com>

ABMC has a helper resctrl_arch_config_cntr() for changing the mapping
between 'cntr_id' and a CLOSID/RMID pair.

Add the helper.

For MPAM this is done by updating the mon->mbwu_idx_to_mon[] array, and as
usual CDP means it needs doing in three different ways.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 drivers/resctrl/mpam_resctrl.c | 37 ++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index e96d320c219c..328a81ab68b4 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -765,6 +765,43 @@ static void mpam_resctrl_pick_counters(void)
 			     mpam_resctrl_counters[QOS_L3_MBM_TOTAL_EVENT_ID].class);
 }
 
+static void __config_cntr(struct mpam_resctrl_mon *mon, u32 cntr_id,
+			  enum resctrl_conf_type cdp_type, u32 closid, u32 rmid,
+			  bool assign)
+{
+	u32 mbwu_idx, mon_idx = resctrl_get_config_index(cntr_id, cdp_type);
+
+	closid = resctrl_get_config_index(closid, cdp_type);
+	mbwu_idx = resctrl_arch_rmid_idx_encode(closid, rmid);
+	WARN_ON_ONCE(mon_idx > l3_num_allocated_mbwu);
+
+	if (assign)
+		mon->mbwu_idx_to_mon[mbwu_idx] = mon->assigned_counters[mon_idx];
+	else
+		mon->mbwu_idx_to_mon[mbwu_idx] = -1;
+}
+
+void resctrl_arch_config_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
+			      enum resctrl_event_id evtid, u32 rmid, u32 closid,
+			      u32 cntr_id, bool assign)
+{
+	struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[evtid];
+
+	if (!mon->mbwu_idx_to_mon || !mon->assigned_counters) {
+		pr_debug("monitor arrays not allocated\n");
+		return;
+	}
+
+	if (cdp_enabled) {
+		__config_cntr(mon, cntr_id, CDP_CODE, closid, rmid, assign);
+		__config_cntr(mon, cntr_id, CDP_DATA, closid, rmid, assign);
+	} else {
+		__config_cntr(mon, cntr_id, CDP_NONE, closid, rmid, assign);
+	}
+
+	resctrl_arch_reset_rmid(r, d, closid, rmid, evtid);
+}
+
 bool resctrl_arch_mbm_cntr_assign_enabled(struct rdt_resource *r)
 {
 	if (r != &mpam_resctrl_controls[RDT_RESOURCE_L3].resctrl_res)
-- 
2.43.0

Re: [PATCH v2 32/45] arm_mpam: resctrl: Add resctrl_arch_config_cntr() for ABMC use

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:34 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> ABMC has a helper resctrl_arch_config_cntr() for changing the mapping
> between 'cntr_id' and a CLOSID/RMID pair.
> 
> Add the helper.
> 
> For MPAM this is done by updating the mon->mbwu_idx_to_mon[] array, and as
> usual CDP means it needs doing in three different ways.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> ---
>  drivers/resctrl/mpam_resctrl.c | 37 ++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
> 
> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> index e96d320c219c..328a81ab68b4 100644
> --- a/drivers/resctrl/mpam_resctrl.c
> +++ b/drivers/resctrl/mpam_resctrl.c
> @@ -765,6 +765,43 @@ static void mpam_resctrl_pick_counters(void)
>  			     mpam_resctrl_counters[QOS_L3_MBM_TOTAL_EVENT_ID].class);
>  }
>  
> +static void __config_cntr(struct mpam_resctrl_mon *mon, u32 cntr_id,
> +			  enum resctrl_conf_type cdp_type, u32 closid, u32 rmid,
> +			  bool assign)
> +{
> +	u32 mbwu_idx, mon_idx = resctrl_get_config_index(cntr_id, cdp_type);
> +
> +	closid = resctrl_get_config_index(closid, cdp_type);
> +	mbwu_idx = resctrl_arch_rmid_idx_encode(closid, rmid);
> +	WARN_ON_ONCE(mon_idx > l3_num_allocated_mbwu);
> +
> +	if (assign)
> +		mon->mbwu_idx_to_mon[mbwu_idx] = mon->assigned_counters[mon_idx];
> +	else
> +		mon->mbwu_idx_to_mon[mbwu_idx] = -1;
> +}

[PATCH v2 33/45] arm_mpam: resctrl: Allow resctrl to allocate monitors

[Ben Horgan]

From: James Morse <james.morse@arm.com>

When resctrl wants to read a domain's 'QOS_L3_OCCUP', it needs to allocate
a monitor on the corresponding resource. Monitors are allocated by class
instead of component.

MBM monitors are much more complicated, if there are enough monitors, they
will be pre-allocated and free-running. If ABMC is in use instead then
'some' are pre-allocated in a different way, and need assigning.

Add helpers to allocate a CSU monitor. These helper return an out of range
value for MBM counters.

Allocating a montitor context is expected to block until hardware resources
become available. This only makes sense for QOS_L3_OCCUP as unallocated MBM
counters are losing data.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Changes since rfc:
USE_RMID_IDX -> USE_PRE_ALLOCATED in comment
Remove unnecessary arch_mon_ctx = NULL
---
 drivers/resctrl/mpam_internal.h | 14 ++++++-
 drivers/resctrl/mpam_resctrl.c  | 67 +++++++++++++++++++++++++++++++++
 include/linux/arm_mpam.h        |  4 ++
 3 files changed, 84 insertions(+), 1 deletion(-)

diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index a2f6956d9236..b907bec96ba5 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -29,6 +29,14 @@ struct platform_device;
 #define PACKED_FOR_KUNIT
 #endif
 
+/*
+ * This 'mon' values must not alias an actual monitor, so must be larger than
+ * U16_MAX, but not be confused with an errno value, so smaller than
+ * (u32)-SZ_4K.
+ * USE_PRE_ALLOCATED is used to avoid confusion with an actual monitor.
+ */
+#define USE_PRE_ALLOCATED	(U16_MAX + 1)
+
 static inline bool mpam_is_enabled(void)
 {
 	return static_branch_likely(&mpam_enabled);
@@ -212,7 +220,11 @@ enum mon_filter_options {
 };
 
 struct mon_cfg {
-	u16			mon;
+	/*
+	 * mon must be large enough to hold out of range values like
+	 * USE_PRE_ALLOCATED
+	 */
+	u32			mon;
 	u8			pmg;
 	bool			match_pmg;
 	bool			csu_exclude_clean;
diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 328a81ab68b4..638c84cdcfb6 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -21,6 +21,8 @@
 
 #include "mpam_internal.h"
 
+DECLARE_WAIT_QUEUE_HEAD(resctrl_mon_ctx_waiters);
+
 /*
  * The classes we've picked to map to resctrl resources, wrapped
  * in with their resctrl structure.
@@ -287,6 +289,71 @@ struct rdt_resource *resctrl_arch_get_resource(enum resctrl_res_level l)
 	return &mpam_resctrl_controls[l].resctrl_res;
 }
 
+static int resctrl_arch_mon_ctx_alloc_no_wait(enum resctrl_event_id evtid)
+{
+	struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[evtid];
+
+	if (!mon->class)
+		return -EINVAL;
+
+	switch (evtid) {
+	case QOS_L3_OCCUP_EVENT_ID:
+		/* With CDP, one monitor gets used for both code/data reads */
+		return mpam_alloc_csu_mon(mon->class);
+	case QOS_L3_MBM_LOCAL_EVENT_ID:
+	case QOS_L3_MBM_TOTAL_EVENT_ID:
+		return USE_PRE_ALLOCATED;
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+void *resctrl_arch_mon_ctx_alloc(struct rdt_resource *r,
+				 enum resctrl_event_id evtid)
+{
+	DEFINE_WAIT(wait);
+	int *ret;
+
+	ret = kmalloc(sizeof(*ret), GFP_KERNEL);
+	if (!ret)
+		return ERR_PTR(-ENOMEM);
+
+	do {
+		prepare_to_wait(&resctrl_mon_ctx_waiters, &wait,
+				TASK_INTERRUPTIBLE);
+		*ret = resctrl_arch_mon_ctx_alloc_no_wait(evtid);
+		if (*ret == -ENOSPC)
+			schedule();
+	} while (*ret == -ENOSPC && !signal_pending(current));
+	finish_wait(&resctrl_mon_ctx_waiters, &wait);
+
+	return ret;
+}
+
+static void resctrl_arch_mon_ctx_free_no_wait(enum resctrl_event_id evtid,
+					      u32 mon_idx)
+{
+	struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[evtid];
+
+	if (!mon->class)
+		return;
+
+	if (evtid == QOS_L3_OCCUP_EVENT_ID)
+		mpam_free_csu_mon(mon->class, mon_idx);
+
+	wake_up(&resctrl_mon_ctx_waiters);
+}
+
+void resctrl_arch_mon_ctx_free(struct rdt_resource *r,
+			       enum resctrl_event_id evtid, void *arch_mon_ctx)
+{
+	u32 mon_idx = *(u32 *)arch_mon_ctx;
+
+	kfree(arch_mon_ctx);
+
+	resctrl_arch_mon_ctx_free_no_wait(evtid, mon_idx);
+}
+
 static bool cache_has_usable_cpor(struct mpam_class *class)
 {
 	struct mpam_props *cprops = &class->props;
diff --git a/include/linux/arm_mpam.h b/include/linux/arm_mpam.h
index 385554ceb452..e1461e32af75 100644
--- a/include/linux/arm_mpam.h
+++ b/include/linux/arm_mpam.h
@@ -63,6 +63,10 @@ u32 resctrl_arch_rmid_idx_encode(u32 closid, u32 rmid);
 void resctrl_arch_rmid_idx_decode(u32 idx, u32 *closid, u32 *rmid);
 u32 resctrl_arch_system_num_rmid_idx(void);
 
+struct rdt_resource;
+void *resctrl_arch_mon_ctx_alloc(struct rdt_resource *r, enum resctrl_event_id evtid);
+void resctrl_arch_mon_ctx_free(struct rdt_resource *r, enum resctrl_event_id evtid, void *ctx);
+
 /**
  * mpam_register_requestor() - Register a requestor with the MPAM driver
  * @partid_max:		The maximum PARTID value the requestor can generate.
-- 
2.43.0

Re: [PATCH v2 33/45] arm_mpam: resctrl: Allow resctrl to allocate monitors

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:35 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> When resctrl wants to read a domain's 'QOS_L3_OCCUP', it needs to allocate
> a monitor on the corresponding resource. Monitors are allocated by class
> instead of component.
> 
> MBM monitors are much more complicated, if there are enough monitors, they
> will be pre-allocated and free-running. If ABMC is in use instead then
> 'some' are pre-allocated in a different way, and need assigning.
> 
> Add helpers to allocate a CSU monitor. These helper return an out of range
> value for MBM counters.
> 
> Allocating a montitor context is expected to block until hardware resources

monitor

> become available. This only makes sense for QOS_L3_OCCUP as unallocated MBM
> counters are losing data.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> ---
> Changes since rfc:
> USE_RMID_IDX -> USE_PRE_ALLOCATED in comment
> Remove unnecessary arch_mon_ctx = NULL
As with some other patches, I'm not taking the time at this point to dig
into all the interactions with resctl as others will cover that much better
than me.

Too much to get done :( 

With that in mind.

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

J

[PATCH v2 34/45] arm_mpam: resctrl: Add resctrl_arch_rmid_read() and resctrl_arch_reset_rmid()

[Ben Horgan]

From: James Morse <james.morse@arm.com>

resctrl uses resctrl_arch_rmid_read() to read counters. CDP emulation means
the counter may need reading in three different ways. The same goes for
reset.

The helpers behind the resctrl_arch_ functions will be re-used for the ABMC
equivalent functions.

Add the rounding helper for checking monitor values while we're here.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Changes since rfc:
cfg intialisation style
code flow at end of read_mon_cdp_safe()
---
 drivers/resctrl/mpam_resctrl.c | 159 +++++++++++++++++++++++++++++++++
 include/linux/arm_mpam.h       |   5 ++
 2 files changed, 164 insertions(+)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 638c84cdcfb6..8a1263986145 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -354,6 +354,165 @@ void resctrl_arch_mon_ctx_free(struct rdt_resource *r,
 	resctrl_arch_mon_ctx_free_no_wait(evtid, mon_idx);
 }
 
+static int
+__read_mon(struct mpam_resctrl_mon *mon, struct mpam_component *mon_comp,
+	   enum mpam_device_features mon_type,
+	   int mon_idx,
+	   enum resctrl_conf_type cdp_type, u32 closid, u32 rmid, u64 *val)
+{
+	struct mon_cfg cfg;
+
+	if (!mpam_is_enabled())
+		return -EINVAL;
+
+	/* Shift closid to account for CDP */
+	closid = resctrl_get_config_index(closid, cdp_type);
+
+	if (mon_idx == USE_PRE_ALLOCATED) {
+		int mbwu_idx = resctrl_arch_rmid_idx_encode(closid, rmid);
+
+		mon_idx = mon->mbwu_idx_to_mon[mbwu_idx];
+		if (mon_idx == -1) {
+			if (mpam_resctrl_abmc_enabled()) {
+				/* Report Unassigned */
+				return -ENOENT;
+			}
+			/* Report Unavailable */
+			return -EINVAL;
+		}
+	}
+
+	if (irqs_disabled()) {
+		/* Check if we can access this domain without an IPI */
+		return -EIO;
+	}
+
+	cfg = (struct mon_cfg) {
+		.mon = mon_idx,
+		.match_pmg = true,
+		.partid = closid,
+		.pmg = rmid,
+	};
+
+	return mpam_msmon_read(mon_comp, &cfg, mon_type, val);
+}
+
+static int read_mon_cdp_safe(struct mpam_resctrl_mon *mon, struct mpam_component *mon_comp,
+			     enum mpam_device_features mon_type,
+			     int mon_idx, u32 closid, u32 rmid, u64 *val)
+{
+	if (cdp_enabled) {
+		u64 code_val = 0, data_val = 0;
+		int err;
+
+		err = __read_mon(mon, mon_comp, mon_type, mon_idx,
+				 CDP_CODE, closid, rmid, &code_val);
+		if (err)
+			return err;
+
+		err = __read_mon(mon, mon_comp, mon_type, mon_idx,
+				 CDP_DATA, closid, rmid, &data_val);
+		if (err)
+			return err;
+
+		*val += code_val + data_val;
+		return 0;
+	}
+
+	return __read_mon(mon, mon_comp, mon_type, mon_idx,
+			  CDP_NONE, closid, rmid, val);
+}
+
+/* MBWU when not in ABMC mode, and CSU counters. */
+int resctrl_arch_rmid_read(struct rdt_resource	*r, struct rdt_mon_domain *d,
+			   u32 closid, u32 rmid, enum resctrl_event_id eventid,
+			   u64 *val, void *arch_mon_ctx)
+{
+	struct mpam_resctrl_dom *l3_dom;
+	struct mpam_component *mon_comp;
+	u32 mon_idx = *(u32 *)arch_mon_ctx;
+	enum mpam_device_features mon_type;
+	struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[eventid];
+
+	resctrl_arch_rmid_read_context_check();
+
+	if (eventid >= QOS_NUM_EVENTS || !mon->class)
+		return -EINVAL;
+
+	l3_dom = container_of(d, struct mpam_resctrl_dom, resctrl_mon_dom);
+	mon_comp = l3_dom->mon_comp[eventid];
+
+	switch (eventid) {
+	case QOS_L3_OCCUP_EVENT_ID:
+		mon_type = mpam_feat_msmon_csu;
+		break;
+	case QOS_L3_MBM_LOCAL_EVENT_ID:
+	case QOS_L3_MBM_TOTAL_EVENT_ID:
+		mon_type = mpam_feat_msmon_mbwu;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return read_mon_cdp_safe(mon, mon_comp, mon_type, mon_idx,
+				 closid, rmid, val);
+}
+
+static void __reset_mon(struct mpam_resctrl_mon *mon, struct mpam_component *mon_comp,
+			int mon_idx,
+			enum resctrl_conf_type cdp_type, u32 closid, u32 rmid)
+{
+	struct mon_cfg cfg = { };
+
+	if (!mpam_is_enabled())
+		return;
+
+	/* Shift closid to account for CDP */
+	closid = resctrl_get_config_index(closid, cdp_type);
+
+	if (mon_idx == USE_PRE_ALLOCATED) {
+		int mbwu_idx = resctrl_arch_rmid_idx_encode(closid, rmid);
+		mon_idx = mon->mbwu_idx_to_mon[mbwu_idx];
+	}
+
+	if (mon_idx == -1)
+		return;
+	cfg.mon = mon_idx;
+	mpam_msmon_reset_mbwu(mon_comp, &cfg);
+}
+
+static void reset_mon_cdp_safe(struct mpam_resctrl_mon *mon, struct mpam_component *mon_comp,
+			       int mon_idx, u32 closid, u32 rmid)
+{
+	if (cdp_enabled) {
+		__reset_mon(mon, mon_comp, mon_idx, CDP_CODE, closid, rmid);
+		__reset_mon(mon, mon_comp, mon_idx, CDP_DATA, closid, rmid);
+	} else {
+		__reset_mon(mon, mon_comp, mon_idx, CDP_NONE, closid, rmid);
+	}
+}
+
+/* Called via IPI. Call with read_cpus_lock() held. */
+void resctrl_arch_reset_rmid(struct rdt_resource *r, struct rdt_mon_domain *d,
+			     u32 closid, u32 rmid, enum resctrl_event_id eventid)
+{
+	struct mpam_resctrl_dom *l3_dom;
+	struct mpam_component *mon_comp;
+	struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[eventid];
+
+	if (!mpam_is_enabled())
+		return;
+
+	/* Only MBWU counters are relevant, and for supported event types. */
+	if (eventid == QOS_L3_OCCUP_EVENT_ID || !mon->class)
+		return;
+
+	l3_dom = container_of(d, struct mpam_resctrl_dom, resctrl_mon_dom);
+	mon_comp = l3_dom->mon_comp[eventid];
+
+	reset_mon_cdp_safe(mon, mon_comp, USE_PRE_ALLOCATED, closid, rmid);
+}
+
 static bool cache_has_usable_cpor(struct mpam_class *class)
 {
 	struct mpam_props *cprops = &class->props;
diff --git a/include/linux/arm_mpam.h b/include/linux/arm_mpam.h
index e1461e32af75..86d5e326d2bd 100644
--- a/include/linux/arm_mpam.h
+++ b/include/linux/arm_mpam.h
@@ -67,6 +67,11 @@ struct rdt_resource;
 void *resctrl_arch_mon_ctx_alloc(struct rdt_resource *r, enum resctrl_event_id evtid);
 void resctrl_arch_mon_ctx_free(struct rdt_resource *r, enum resctrl_event_id evtid, void *ctx);
 
+static inline unsigned int resctrl_arch_round_mon_val(unsigned int val)
+{
+	return val;
+}
+
 /**
  * mpam_register_requestor() - Register a requestor with the MPAM driver
  * @partid_max:		The maximum PARTID value the requestor can generate.
-- 
2.43.0

Re: [PATCH v2 34/45] arm_mpam: resctrl: Add resctrl_arch_rmid_read() and resctrl_arch_reset_rmid()

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:36 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> resctrl uses resctrl_arch_rmid_read() to read counters. CDP emulation means
> the counter may need reading in three different ways. The same goes for
> reset.
> 
> The helpers behind the resctrl_arch_ functions will be re-used for the ABMC
> equivalent functions.
> 
> Add the rounding helper for checking monitor values while we're here.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Trivial stuff only.
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> ---
> Changes since rfc:
> cfg intialisation style
> code flow at end of read_mon_cdp_safe()
> ---
>  drivers/resctrl/mpam_resctrl.c | 159 +++++++++++++++++++++++++++++++++
>  include/linux/arm_mpam.h       |   5 ++
>  2 files changed, 164 insertions(+)
> 
> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> index 638c84cdcfb6..8a1263986145 100644
> --- a/drivers/resctrl/mpam_resctrl.c
> +++ b/drivers/resctrl/mpam_resctrl.c
> @@ -354,6 +354,165 @@ void resctrl_arch_mon_ctx_free(struct rdt_resource *r,
>  	resctrl_arch_mon_ctx_free_no_wait(evtid, mon_idx);
>  }
>  
> +static int
Whilst I don't really care, this does seem inconsistent from other functions
static int __read_mon(...
probably for consistent looking code.

> +__read_mon(struct mpam_resctrl_mon *mon, struct mpam_component *mon_comp,
> +	   enum mpam_device_features mon_type,
> +	   int mon_idx,
> +	   enum resctrl_conf_type cdp_type, u32 closid, u32 rmid, u64 *val)
> +{
> +	struct mon_cfg cfg;
> +
> +	if (!mpam_is_enabled())
> +		return -EINVAL;
> +
> +	/* Shift closid to account for CDP */
> +	closid = resctrl_get_config_index(closid, cdp_type);
> +
> +	if (mon_idx == USE_PRE_ALLOCATED) {
> +		int mbwu_idx = resctrl_arch_rmid_idx_encode(closid, rmid);
> +
> +		mon_idx = mon->mbwu_idx_to_mon[mbwu_idx];
> +		if (mon_idx == -1) {
> +			if (mpam_resctrl_abmc_enabled()) {
> +				/* Report Unassigned */
> +				return -ENOENT;
> +			}
> +			/* Report Unavailable */
> +			return -EINVAL;
> +		}
> +	}
> +
> +	if (irqs_disabled()) {
> +		/* Check if we can access this domain without an IPI */
> +		return -EIO;
> +	}
> +
> +	cfg = (struct mon_cfg) {
> +		.mon = mon_idx,
> +		.match_pmg = true,
> +		.partid = closid,
> +		.pmg = rmid,
> +	};
> +
> +	return mpam_msmon_read(mon_comp, &cfg, mon_type, val);
> +}

> +/* MBWU when not in ABMC mode, and CSU counters. */
> +int resctrl_arch_rmid_read(struct rdt_resource	*r, struct rdt_mon_domain *d,

Odd tab before *r.

> +			   u32 closid, u32 rmid, enum resctrl_event_id eventid,
> +			   u64 *val, void *arch_mon_ctx)
> +{
> +	struct mpam_resctrl_dom *l3_dom;
> +	struct mpam_component *mon_comp;
> +	u32 mon_idx = *(u32 *)arch_mon_ctx;
> +	enum mpam_device_features mon_type;
> +	struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[eventid];
> +
> +	resctrl_arch_rmid_read_context_check();
> +
> +	if (eventid >= QOS_NUM_EVENTS || !mon->class)
> +		return -EINVAL;
> +
> +	l3_dom = container_of(d, struct mpam_resctrl_dom, resctrl_mon_dom);
> +	mon_comp = l3_dom->mon_comp[eventid];
> +
> +	switch (eventid) {
> +	case QOS_L3_OCCUP_EVENT_ID:
> +		mon_type = mpam_feat_msmon_csu;
> +		break;
> +	case QOS_L3_MBM_LOCAL_EVENT_ID:
> +	case QOS_L3_MBM_TOTAL_EVENT_ID:
> +		mon_type = mpam_feat_msmon_mbwu;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return read_mon_cdp_safe(mon, mon_comp, mon_type, mon_idx,
> +				 closid, rmid, val);
> +}

[PATCH v2 35/45] arm_mpam: resctrl: Add resctrl_arch_cntr_read() & resctrl_arch_reset_cntr()

[Ben Horgan]

From: James Morse <james.morse@arm.com>

When used in ABMC mode, resctrl uses a different set of helpers to read and
reset the counters.

Add these.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 drivers/resctrl/mpam_resctrl.c | 43 ++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 8a1263986145..ef60bc0c7bd8 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -458,6 +458,28 @@ int resctrl_arch_rmid_read(struct rdt_resource	*r, struct rdt_mon_domain *d,
 				 closid, rmid, val);
 }
 
+/* MBWU counters when in ABMC mode */
+int resctrl_arch_cntr_read(struct rdt_resource *r, struct rdt_mon_domain *d,
+			   u32 closid, u32 rmid, int mon_idx,
+			   enum resctrl_event_id eventid, u64 *val)
+{
+	struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[eventid];
+	struct mpam_resctrl_dom *l3_dom;
+	struct mpam_component *mon_comp;
+
+	if (!mpam_is_enabled())
+		return -EINVAL;
+
+	if (eventid == QOS_L3_OCCUP_EVENT_ID || !mon->class)
+		return -EINVAL;
+
+	l3_dom = container_of(d, struct mpam_resctrl_dom, resctrl_mon_dom);
+	mon_comp = l3_dom->mon_comp[eventid];
+
+	return read_mon_cdp_safe(mon, mon_comp, mpam_feat_msmon_mbwu, mon_idx,
+				 closid, rmid, val);
+}
+
 static void __reset_mon(struct mpam_resctrl_mon *mon, struct mpam_component *mon_comp,
 			int mon_idx,
 			enum resctrl_conf_type cdp_type, u32 closid, u32 rmid)
@@ -513,6 +535,27 @@ void resctrl_arch_reset_rmid(struct rdt_resource *r, struct rdt_mon_domain *d,
 	reset_mon_cdp_safe(mon, mon_comp, USE_PRE_ALLOCATED, closid, rmid);
 }
 
+/* Reset an assigned counter */
+void resctrl_arch_reset_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
+			     u32 closid, u32 rmid, int cntr_id,
+			     enum resctrl_event_id eventid)
+{
+	struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[eventid];
+	struct mpam_resctrl_dom *l3_dom;
+	struct mpam_component *mon_comp;
+
+	if (!mpam_is_enabled())
+		return;
+
+	if (eventid == QOS_L3_OCCUP_EVENT_ID || !mon->class)
+		return;
+
+	l3_dom = container_of(d, struct mpam_resctrl_dom, resctrl_mon_dom);
+	mon_comp = l3_dom->mon_comp[eventid];
+
+	reset_mon_cdp_safe(mon, mon_comp, USE_PRE_ALLOCATED, closid, rmid);
+}
+
 static bool cache_has_usable_cpor(struct mpam_class *class)
 {
 	struct mpam_props *cprops = &class->props;
-- 
2.43.0

Re: [PATCH v2 35/45] arm_mpam: resctrl: Add resctrl_arch_cntr_read() & resctrl_arch_reset_cntr()

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:37 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> When used in ABMC mode, resctrl uses a different set of helpers to read and
> reset the counters.
> 
> Add these.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

[PATCH v2 36/45] arm_mpam: resctrl: Update the rmid reallocation limit

[Ben Horgan]

From: James Morse <james.morse@arm.com>

resctrl's limbo code needs to be told when the data left in a cache is
small enough for the partid+pmg value to be re-allocated.

x86 uses the cache size divided by the number of rmid users the cache may
have. Do the same, but for the smallest cache, and with the number of
partid-and-pmg users.

Querying the cache size can't happen until after cacheinfo_sysfs_init() has
run, so mpam_resctrl_setup() must wait until then.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 drivers/resctrl/mpam_resctrl.c | 54 ++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index ef60bc0c7bd8..84f517cb047a 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -16,6 +16,7 @@
 #include <linux/resctrl.h>
 #include <linux/slab.h>
 #include <linux/types.h>
+#include <linux/wait.h>
 
 #include <asm/mpam.h>
 
@@ -52,6 +53,13 @@ static bool exposed_mon_capable;
  */
 static bool cdp_enabled;
 
+/*
+ * mpam_resctrl_pick_caches() needs to know the size of the caches. cacheinfo
+ * populates this from a device_initcall(). mpam_resctrl_setup() must wait.
+ */
+static bool cacheinfo_ready;
+static DECLARE_WAIT_QUEUE_HEAD(wait_cacheinfo_ready);
+
 /*
  * L3 local/total may come from different classes - what is the number of MBWU
  * 'on L3'?
@@ -556,6 +564,38 @@ void resctrl_arch_reset_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
 	reset_mon_cdp_safe(mon, mon_comp, USE_PRE_ALLOCATED, closid, rmid);
 }
 
+/*
+ * The rmid realloc threshold should be for the smallest cache exposed to
+ * resctrl.
+ */
+static int update_rmid_limits(struct mpam_class *class)
+{
+	u32 num_unique_pmg = resctrl_arch_system_num_rmid_idx();
+	struct mpam_props *cprops = &class->props;
+	struct cacheinfo *ci;
+
+	lockdep_assert_cpus_held();
+
+	/* Assume cache levels are the same size for all CPUs... */
+	ci = get_cpu_cacheinfo_level(smp_processor_id(), class->level);
+	if (!ci || ci->size == 0) {
+		pr_debug("Could not read cache size for class %u\n",
+			 class->level);
+		return -EINVAL;
+	}
+
+	if (!mpam_has_feature(mpam_feat_msmon_csu, cprops))
+		return 0;
+
+	if (!resctrl_rmid_realloc_limit ||
+	    ci->size < resctrl_rmid_realloc_limit) {
+		resctrl_rmid_realloc_limit = ci->size;
+		resctrl_rmid_realloc_threshold = ci->size / num_unique_pmg;
+	}
+
+	return 0;
+}
+
 static bool cache_has_usable_cpor(struct mpam_class *class)
 {
 	struct mpam_props *cprops = &class->props;
@@ -996,6 +1036,9 @@ static void mpam_resctrl_pick_counters(void)
 			/* CSU counters only make sense on a cache. */
 			switch (class->type) {
 			case MPAM_CLASS_CACHE:
+				if (update_rmid_limits(class))
+					continue;
+
 				counter_update_class(QOS_L3_OCCUP_EVENT_ID, class);
 				return;
 			default:
@@ -1708,6 +1751,8 @@ int mpam_resctrl_setup(void)
 	int err = 0;
 	struct mpam_resctrl_res *res;
 
+	wait_event(wait_cacheinfo_ready, cacheinfo_ready);
+
 	cpus_read_lock();
 	for (enum resctrl_res_level i = 0; i < RDT_NUM_RESOURCES; i++) {
 		res = &mpam_resctrl_controls[i];
@@ -1773,6 +1818,15 @@ int mpam_resctrl_setup(void)
 	return err;
 }
 
+static int __init __cacheinfo_ready(void)
+{
+	cacheinfo_ready = true;
+	wake_up(&wait_cacheinfo_ready);
+
+	return 0;
+}
+device_initcall_sync(__cacheinfo_ready);
+
 #ifdef CONFIG_MPAM_KUNIT_TEST
 #include "test_mpam_resctrl.c"
 #endif
-- 
2.43.0

Re: [PATCH v2 36/45] arm_mpam: resctrl: Update the rmid reallocation limit

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:38 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> resctrl's limbo code needs to be told when the data left in a cache is
> small enough for the partid+pmg value to be re-allocated.
> 
> x86 uses the cache size divided by the number of rmid users the cache may
> have. Do the same, but for the smallest cache, and with the number of
> partid-and-pmg users.
> 
> Querying the cache size can't happen until after cacheinfo_sysfs_init() has
> run, so mpam_resctrl_setup() must wait until then.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

[PATCH v2 37/45] arm_mpam: resctrl: Add empty definitions for assorted resctrl functions

[Ben Horgan]

From: James Morse <james.morse@arm.com>

A few resctrl features and hooks need to be provided, but aren't needed or
supported on MPAM platforms.

resctrl has individual hooks to separately enable and disable the
closid/partid and rmid/pmg context switching code. For MPAM this is all the
same thing, as the value in struct task_struct is used to cache the value
that should be written to hardware. arm64's context switching code is
enabled once MPAM is usable, but doesn't touch the hardware unless the
value has changed.

For now event configuration is not supported, and can be turned off by
returning 'false' from resctrl_arch_is_evt_configurable().

The new io_alloc feature is not supported either, always return false from
the enable helper to indicate and fail the enable.

Add this, and empty definitions for the other hooks.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 drivers/resctrl/mpam_resctrl.c | 27 +++++++++++++++++++++++++++
 include/linux/arm_mpam.h       |  9 +++++++++
 2 files changed, 36 insertions(+)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 84f517cb047a..059148c38a38 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -93,6 +93,23 @@ bool resctrl_arch_mon_capable(void)
 	return exposed_mon_capable;
 }
 
+bool resctrl_arch_is_evt_configurable(enum resctrl_event_id evt)
+{
+	return false;
+}
+
+void resctrl_arch_mon_event_config_read(void *info)
+{
+}
+
+void resctrl_arch_mon_event_config_write(void *info)
+{
+}
+
+void resctrl_arch_reset_rmid_all(struct rdt_resource *r, struct rdt_mon_domain *d)
+{
+}
+
 bool resctrl_arch_get_cdp_enabled(enum resctrl_res_level rid)
 {
 	switch (rid) {
@@ -1131,6 +1148,16 @@ int resctrl_arch_mbm_cntr_assign_set(struct rdt_resource *r, bool enable)
 	return 0;
 }
 
+int resctrl_arch_io_alloc_enable(struct rdt_resource *r, bool enable)
+{
+	return -EOPNOTSUPP;
+}
+
+bool resctrl_arch_get_io_alloc_enabled(struct rdt_resource *r)
+{
+	return false;
+}
+
 static int mpam_resctrl_control_init(struct mpam_resctrl_res *res,
 				     enum resctrl_res_level type)
 {
diff --git a/include/linux/arm_mpam.h b/include/linux/arm_mpam.h
index 86d5e326d2bd..f92a36187a52 100644
--- a/include/linux/arm_mpam.h
+++ b/include/linux/arm_mpam.h
@@ -67,6 +67,15 @@ struct rdt_resource;
 void *resctrl_arch_mon_ctx_alloc(struct rdt_resource *r, enum resctrl_event_id evtid);
 void resctrl_arch_mon_ctx_free(struct rdt_resource *r, enum resctrl_event_id evtid, void *ctx);
 
+/*
+ * The CPU configuration for MPAM is cheap to write, and is only written if it
+ * has changed. No need for fine grained enables.
+ */
+static inline void resctrl_arch_enable_mon(void) { }
+static inline void resctrl_arch_disable_mon(void) { }
+static inline void resctrl_arch_enable_alloc(void) { }
+static inline void resctrl_arch_disable_alloc(void) { }
+
 static inline unsigned int resctrl_arch_round_mon_val(unsigned int val)
 {
 	return val;
-- 
2.43.0

Re: [PATCH v2 37/45] arm_mpam: resctrl: Add empty definitions for assorted resctrl functions

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:39 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> A few resctrl features and hooks need to be provided, but aren't needed or
> supported on MPAM platforms.
> 
> resctrl has individual hooks to separately enable and disable the
> closid/partid and rmid/pmg context switching code. For MPAM this is all the
> same thing, as the value in struct task_struct is used to cache the value
> that should be written to hardware. arm64's context switching code is
> enabled once MPAM is usable, but doesn't touch the hardware unless the
> value has changed.
> 
> For now event configuration is not supported, and can be turned off by
> returning 'false' from resctrl_arch_is_evt_configurable().
> 
> The new io_alloc feature is not supported either, always return false from
> the enable helper to indicate and fail the enable.
> 
> Add this, and empty definitions for the other hooks.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>

FWIW given I didn't check what these all are, just that they are indeed
stubs that do the obvious things.

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
> ---
>  drivers/resctrl/mpam_resctrl.c | 27 +++++++++++++++++++++++++++
>  include/linux/arm_mpam.h       |  9 +++++++++
>  2 files changed, 36 insertions(+)
> 
> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> index 84f517cb047a..059148c38a38 100644
> --- a/drivers/resctrl/mpam_resctrl.c
> +++ b/drivers/resctrl/mpam_resctrl.c
> @@ -93,6 +93,23 @@ bool resctrl_arch_mon_capable(void)
>  	return exposed_mon_capable;
>  }
>  
> +bool resctrl_arch_is_evt_configurable(enum resctrl_event_id evt)
> +{
> +	return false;
> +}
> +
> +void resctrl_arch_mon_event_config_read(void *info)
> +{
> +}
> +
> +void resctrl_arch_mon_event_config_write(void *info)
> +{
> +}
> +
> +void resctrl_arch_reset_rmid_all(struct rdt_resource *r, struct rdt_mon_domain *d)
> +{
> +}
> +
>  bool resctrl_arch_get_cdp_enabled(enum resctrl_res_level rid)
>  {
>  	switch (rid) {
> @@ -1131,6 +1148,16 @@ int resctrl_arch_mbm_cntr_assign_set(struct rdt_resource *r, bool enable)
>  	return 0;
>  }
>  
> +int resctrl_arch_io_alloc_enable(struct rdt_resource *r, bool enable)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +bool resctrl_arch_get_io_alloc_enabled(struct rdt_resource *r)
> +{
> +	return false;
> +}
> +
>  static int mpam_resctrl_control_init(struct mpam_resctrl_res *res,
>  				     enum resctrl_res_level type)
>  {
> diff --git a/include/linux/arm_mpam.h b/include/linux/arm_mpam.h
> index 86d5e326d2bd..f92a36187a52 100644
> --- a/include/linux/arm_mpam.h
> +++ b/include/linux/arm_mpam.h
> @@ -67,6 +67,15 @@ struct rdt_resource;
>  void *resctrl_arch_mon_ctx_alloc(struct rdt_resource *r, enum resctrl_event_id evtid);
>  void resctrl_arch_mon_ctx_free(struct rdt_resource *r, enum resctrl_event_id evtid, void *ctx);
>  
> +/*
> + * The CPU configuration for MPAM is cheap to write, and is only written if it
> + * has changed. No need for fine grained enables.
> + */
> +static inline void resctrl_arch_enable_mon(void) { }
> +static inline void resctrl_arch_disable_mon(void) { }
> +static inline void resctrl_arch_enable_alloc(void) { }
> +static inline void resctrl_arch_disable_alloc(void) { }
> +
>  static inline unsigned int resctrl_arch_round_mon_val(unsigned int val)
>  {
>  	return val;

[PATCH v2 38/45] arm64: mpam: Select ARCH_HAS_CPU_RESCTRL

[Ben Horgan]

From: James Morse <james.morse@arm.com>

Enough MPAM support is present to enable ARCH_HAS_CPU_RESCTRL.  Let it
rip^Wlink!

ARCH_HAS_CPU_RESCTRL indicates resctrl can be enabled. It is enabled by the
arch code simply because it has 'arch' in its name.

This removes ARM_CPU_RESCTRL as a mimic of X86_CPU_RESCTRL.  While here,
move the ACPI dependency to the driver's Kconfig file.

In anticipation of MPAM being useful remove the CONFIG_EXPERT restriction.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 arch/arm64/Kconfig               | 4 ++--
 arch/arm64/include/asm/resctrl.h | 2 ++
 drivers/resctrl/Kconfig          | 9 ++++++++-
 drivers/resctrl/Makefile         | 2 +-
 4 files changed, 13 insertions(+), 4 deletions(-)
 create mode 100644 arch/arm64/include/asm/resctrl.h

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index cdcc5b76a110..baeecb88771d 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -2026,8 +2026,8 @@ config ARM64_TLB_RANGE
 
 config ARM64_MPAM
 	bool "Enable support for MPAM"
-	select ARM64_MPAM_DRIVER if EXPERT	# does nothing yet
-	select ACPI_MPAM if ACPI
+	select ARM64_MPAM_DRIVER
+	select ARCH_HAS_CPU_RESCTRL
 	help
 	  Memory System Resource Partitioning and Monitoring (MPAM) is an
 	  optional extension to the Arm architecture that allows each
diff --git a/arch/arm64/include/asm/resctrl.h b/arch/arm64/include/asm/resctrl.h
new file mode 100644
index 000000000000..b506e95cf6e3
--- /dev/null
+++ b/arch/arm64/include/asm/resctrl.h
@@ -0,0 +1,2 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/arm_mpam.h>
diff --git a/drivers/resctrl/Kconfig b/drivers/resctrl/Kconfig
index c808e0470394..672abea3b03c 100644
--- a/drivers/resctrl/Kconfig
+++ b/drivers/resctrl/Kconfig
@@ -1,6 +1,7 @@
 menuconfig ARM64_MPAM_DRIVER
 	bool "MPAM driver"
-	depends on ARM64 && ARM64_MPAM && EXPERT
+	depends on ARM64 && ARM64_MPAM
+	select ACPI_MPAM if ACPI
 	help
 	  Memory System Resource Partitioning and Monitoring (MPAM) driver for
 	  System IP, e.g. caches and memory controllers.
@@ -22,3 +23,9 @@ config MPAM_KUNIT_TEST
 	  If unsure, say N.
 
 endif
+
+config ARM64_MPAM_RESCTRL_FS
+	bool
+	default y if ARM64_MPAM_DRIVER && RESCTRL_FS
+	select RESCTRL_RMID_DEPENDS_ON_CLOSID
+	select RESCTRL_ASSIGN_FIXED
diff --git a/drivers/resctrl/Makefile b/drivers/resctrl/Makefile
index 40beaf999582..4f6d0e81f9b8 100644
--- a/drivers/resctrl/Makefile
+++ b/drivers/resctrl/Makefile
@@ -1,5 +1,5 @@
 obj-$(CONFIG_ARM64_MPAM_DRIVER)			+= mpam.o
 mpam-y						+= mpam_devices.o
-mpam-$(CONFIG_ARM_CPU_RESCTRL)			+= mpam_resctrl.o
+mpam-$(CONFIG_ARM64_MPAM_RESCTRL_FS)		+= mpam_resctrl.o
 
 ccflags-$(CONFIG_ARM64_MPAM_DRIVER_DEBUG)	+= -DDEBUG
-- 
2.43.0

Re: [PATCH v2 38/45] arm64: mpam: Select ARCH_HAS_CPU_RESCTRL

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:40 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> Enough MPAM support is present to enable ARCH_HAS_CPU_RESCTRL.  Let it
> rip^Wlink!
> 
> ARCH_HAS_CPU_RESCTRL indicates resctrl can be enabled. It is enabled by the
> arch code simply because it has 'arch' in its name.
> 
> This removes ARM_CPU_RESCTRL as a mimic of X86_CPU_RESCTRL.  While here,
> move the ACPI dependency to the driver's Kconfig file.
> 
> In anticipation of MPAM being useful remove the CONFIG_EXPERT restriction.
Lol. I hope it is useful :)
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

[PATCH v2 39/45] arm_mpam: resctrl: Call resctrl_init() on platforms that can support resctrl

[Ben Horgan]

From: James Morse <james.morse@arm.com>

Now that MPAM links against resctrl, call resctrl_init() to register the
filesystem and setup resctrl's structures.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 drivers/resctrl/mpam_devices.c  | 32 +++++++++++--
 drivers/resctrl/mpam_internal.h |  4 ++
 drivers/resctrl/mpam_resctrl.c  | 82 ++++++++++++++++++++++++++++++++-
 3 files changed, 113 insertions(+), 5 deletions(-)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 4f5d908d02a9..c20b2757b86b 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -73,6 +73,14 @@ static DECLARE_WORK(mpam_broken_work, &mpam_disable);
 /* When mpam is disabled, the printed reason to aid debugging */
 static char *mpam_disable_reason;
 
+/*
+ * Whether resctrl has been setup. Used by cpuhp in preference to
+ * mpam_is_enabled(). The disable call after an error interrupt makes
+ * mpam_is_enabled() false before the cpuhp callbacks are made.
+ * Reads/writes should hold mpam_cpuhp_state_lock, (or be cpuhp callbacks).
+ */
+static bool mpam_resctrl_enabled;
+
 /*
  * An MSC is a physical container for controls and monitors, each identified by
  * their RIS index. These share a base-address, interrupts and some MMIO
@@ -1628,7 +1636,7 @@ static int mpam_cpu_online(unsigned int cpu)
 			mpam_reprogram_msc(msc);
 	}
 
-	if (mpam_is_enabled())
+	if (mpam_resctrl_enabled)
 		mpam_resctrl_online_cpu(cpu);
 
 	return 0;
@@ -1674,7 +1682,7 @@ static int mpam_cpu_offline(unsigned int cpu)
 {
 	struct mpam_msc *msc;
 
-	if (mpam_is_enabled())
+	if (mpam_resctrl_enabled)
 		mpam_resctrl_offline_cpu(cpu);
 
 	guard(srcu)(&mpam_srcu);
@@ -2536,6 +2544,7 @@ static void mpam_enable_once(void)
 	}
 
 	static_branch_enable(&mpam_enabled);
+	mpam_resctrl_enabled = true;
 	mpam_register_cpuhp_callbacks(mpam_cpu_online, mpam_cpu_offline,
 				      "mpam:online");
 
@@ -2595,24 +2604,39 @@ void mpam_reset_class(struct mpam_class *class)
 void mpam_disable(struct work_struct *ignored)
 {
 	int idx;
+	bool do_resctrl_exit;
 	struct mpam_class *class;
 	struct mpam_msc *msc, *tmp;
 
+	if (mpam_is_enabled())
+		static_branch_disable(&mpam_enabled);
+
 	mutex_lock(&mpam_cpuhp_state_lock);
 	if (mpam_cpuhp_state) {
 		cpuhp_remove_state(mpam_cpuhp_state);
 		mpam_cpuhp_state = 0;
 	}
+
+	/*
+	 * Removing the cpuhp state called mpam_cpu_offline() and told resctrl
+	 * all the CPUs are offline.
+	 */
+	do_resctrl_exit = mpam_resctrl_enabled;
+	mpam_resctrl_enabled = false;
 	mutex_unlock(&mpam_cpuhp_state_lock);
 
-	static_branch_disable(&mpam_enabled);
+	if (do_resctrl_exit)
+		mpam_resctrl_exit();
 
 	mpam_unregister_irqs();
 
 	idx = srcu_read_lock(&mpam_srcu);
 	list_for_each_entry_srcu(class, &mpam_classes, classes_list,
-				 srcu_read_lock_held(&mpam_srcu))
+				 srcu_read_lock_held(&mpam_srcu)) {
 		mpam_reset_class(class);
+		if (do_resctrl_exit)
+			mpam_resctrl_teardown_class(class);
+	}
 	srcu_read_unlock(&mpam_srcu, idx);
 
 	mutex_lock(&mpam_list_lock);
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index b907bec96ba5..9a3996decda5 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -447,12 +447,16 @@ int mpam_get_cpumask_from_cache_id(unsigned long cache_id, u32 cache_level,
 
 #ifdef CONFIG_RESCTRL_FS
 int mpam_resctrl_setup(void);
+void mpam_resctrl_exit(void);
 int mpam_resctrl_online_cpu(unsigned int cpu);
 void mpam_resctrl_offline_cpu(unsigned int cpu);
+void mpam_resctrl_teardown_class(struct mpam_class *class);
 #else
 static inline int mpam_resctrl_setup(void) { return 0; }
+static inline void mpam_resctrl_exit(void) { }
 static inline int mpam_resctrl_online_cpu(unsigned int cpu) { return 0; }
 static inline void mpam_resctrl_offline_cpu(unsigned int cpu) { }
+static inline void mpam_resctrl_teardown_class(struct mpam_class *class) { }
 #endif /* CONFIG_RESCTRL_FS */
 
 /*
diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 059148c38a38..bbb12b5dfd8c 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -53,6 +53,12 @@ static bool exposed_mon_capable;
  */
 static bool cdp_enabled;
 
+/*
+ * If resctrl_init() succeeded, resctrl_exit() can be used to remove support
+ * for the filesystem in the event of an error.
+ */
+static bool resctrl_enabled;
+
 /*
  * mpam_resctrl_pick_caches() needs to know the size of the caches. cacheinfo
  * populates this from a device_initcall(). mpam_resctrl_setup() must wait.
@@ -318,6 +324,9 @@ static int resctrl_arch_mon_ctx_alloc_no_wait(enum resctrl_event_id evtid)
 {
 	struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[evtid];
 
+	if (!mpam_is_enabled())
+		return -EINVAL;
+
 	if (!mon->class)
 		return -EINVAL;
 
@@ -360,6 +369,9 @@ static void resctrl_arch_mon_ctx_free_no_wait(enum resctrl_event_id evtid,
 {
 	struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[evtid];
 
+	if (!mpam_is_enabled())
+		return;
+
 	if (!mon->class)
 		return;
 
@@ -461,6 +473,9 @@ int resctrl_arch_rmid_read(struct rdt_resource	*r, struct rdt_mon_domain *d,
 
 	resctrl_arch_rmid_read_context_check();
 
+	if (!mpam_is_enabled())
+		return -EINVAL;
+
 	if (eventid >= QOS_NUM_EVENTS || !mon->class)
 		return -EINVAL;
 
@@ -1399,6 +1414,9 @@ int resctrl_arch_update_one(struct rdt_resource *r, struct rdt_ctrl_domain *d,
 	lockdep_assert_cpus_held();
 	lockdep_assert_irqs_enabled();
 
+	if (!mpam_is_enabled())
+		return -EINVAL;
+
 	/*
 	 * No need to check the CPU as mpam_apply_config() doesn't care, and
 	 * resctrl_arch_update_domains() relies on this.
@@ -1461,6 +1479,9 @@ int resctrl_arch_update_domains(struct rdt_resource *r, u32 closid)
 	lockdep_assert_cpus_held();
 	lockdep_assert_irqs_enabled();
 
+	if (!mpam_is_enabled())
+		return -EINVAL;
+
 	list_for_each_entry_rcu(d, &r->ctrl_domains, hdr.list) {
 		for (enum resctrl_conf_type t = 0; t < CDP_NUM_TYPES; t++) {
 			struct resctrl_staged_config *cfg = &d->staged_config[t];
@@ -1840,11 +1861,70 @@ int mpam_resctrl_setup(void)
 		pr_warn("Number of PMG is not a power of 2! resctrl may misbehave");
 	}
 
-	/* TODO: call resctrl_init() */
+	err = resctrl_init();
+	if (!err)
+		WRITE_ONCE(resctrl_enabled, true);
 
 	return err;
 }
 
+void mpam_resctrl_exit(void)
+{
+	if (!READ_ONCE(resctrl_enabled))
+		return;
+
+	WRITE_ONCE(resctrl_enabled, false);
+	resctrl_exit();
+}
+
+static void mpam_resctrl_teardown_mon(struct mpam_resctrl_mon *mon, struct mpam_class *class)
+{
+	u32 num_mbwu_mon = l3_num_allocated_mbwu;
+
+	if (!mon->mbwu_idx_to_mon)
+		return;
+
+	if (mon->assigned_counters) {
+		__free_mbwu_mon(class, mon->assigned_counters, num_mbwu_mon);
+		mon->assigned_counters = NULL;
+		kfree(mon->mbwu_idx_to_mon);
+	} else {
+		__free_mbwu_mon(class, mon->mbwu_idx_to_mon, num_mbwu_mon);
+	}
+	mon->mbwu_idx_to_mon = NULL;
+}
+
+/*
+ * The driver is detaching an MSC from this class, if resctrl was using it,
+ * pull on resctrl_exit().
+ */
+void mpam_resctrl_teardown_class(struct mpam_class *class)
+{
+	int i;
+	struct mpam_resctrl_res *res;
+	struct mpam_resctrl_mon *mon;
+
+	might_sleep();
+
+	for (i = 0; i < RDT_NUM_RESOURCES; i++) {
+		res = &mpam_resctrl_controls[i];
+		if (res->class == class) {
+			res->class = NULL;
+			break;
+		}
+	}
+	for (i = 0; i < QOS_NUM_EVENTS; i++) {
+		mon = &mpam_resctrl_counters[i];
+		if (mon->class == class) {
+			mon->class = NULL;
+
+			mpam_resctrl_teardown_mon(mon, class);
+
+			break;
+		}
+	}
+}
+
 static int __init __cacheinfo_ready(void)
 {
 	cacheinfo_ready = true;
-- 
2.43.0

Re: [PATCH v2 39/45] arm_mpam: resctrl: Call resctrl_init() on platforms that can support resctrl

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:41 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> Now that MPAM links against resctrl, call resctrl_init() to register the
> filesystem and setup resctrl's structures.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>

Just minor suggestions inline.  I'm not sure the for loop macros
are worth doing but that particular pair of loops feel awfully familiar
at this point, so maybe. 

Either way..

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
 
> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> index 059148c38a38..bbb12b5dfd8c 100644
> --- a/drivers/resctrl/mpam_resctrl.c
> +++ b/drivers/resctrl/mpam_resctrl.c

> @@ -1840,11 +1861,70 @@ int mpam_resctrl_setup(void)
>  		pr_warn("Number of PMG is not a power of 2! resctrl may misbehave");
>  	}
>  
> -	/* TODO: call resctrl_init() */
> +	err = resctrl_init();
> +	if (!err)
> +		WRITE_ONCE(resctrl_enabled, true);

Trivial but I'd prefer the error path out of line.

	if (err)
		return err;

	WRITE_ONCE(resctrl_enabled, true);
	
	return 0;
>  
>  	return err;
>  }

> +
> +/*
> + * The driver is detaching an MSC from this class, if resctrl was using it,
> + * pull on resctrl_exit().
> + */
> +void mpam_resctrl_teardown_class(struct mpam_class *class)
> +{
> +	int i;
> +	struct mpam_resctrl_res *res;
> +	struct mpam_resctrl_mon *mon;
> +
> +	might_sleep();
> +
> +	for (i = 0; i < RDT_NUM_RESOURCES; i++) {
There are enough iterators over these that I wonder
if it is worth some macros.
 
	for_each_mpam_resctrl_control(res) {
	}
and
	for_each_mpam_resctrl_counter(mon) {
	}


> +		res = &mpam_resctrl_controls[i];
> +		if (res->class == class) {
> +			res->class = NULL;
> +			break;
> +		}
> +	}
> +	for (i = 0; i < QOS_NUM_EVENTS; i++) {
> +		mon = &mpam_resctrl_counters[i];
> +		if (mon->class == class) {
> +			mon->class = NULL;
> +
> +			mpam_resctrl_teardown_mon(mon, class);
> +
> +			break;
> +		}
> +	}
> +}
> +
>  static int __init __cacheinfo_ready(void)
>  {
>  	cacheinfo_ready = true;

[PATCH v2 40/45] arm_mpam: Generate a configuration for min controls

[Ben Horgan]

From: James Morse <james.morse@arm.com>

MPAM supports a minimum and maximum control for memory bandwidth. The
purpose of the minimum control is to give priority to tasks that are below
their minimum value. Resctrl only provides one value for the bandwidth
configuration, which is used for the maximum.

The minimum control is always programmed to zero on hardware that supports
it.

Generate a minimum bandwidth value that is 5% lower than the value provided
by resctrl. This means tasks that are not receiving their target bandwidth
can be prioritised by the hardware.

For component reset reuse the same calculation so that the default is a
value resctrl can set.

CC: Zeng Heng <zengheng4@huawei.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Add reset_mbw_min
Clear min cfg when setting max
use mpam_extend_config on component reset
---
 drivers/resctrl/mpam_devices.c      | 76 +++++++++++++++++++++++++++--
 drivers/resctrl/mpam_internal.h     |  3 ++
 drivers/resctrl/mpam_resctrl.c      |  2 +
 drivers/resctrl/test_mpam_devices.c | 66 +++++++++++++++++++++++++
 4 files changed, 142 insertions(+), 5 deletions(-)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index c20b2757b86b..deea46c2a6c3 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -721,6 +721,13 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
 			mpam_set_feature(mpam_feat_mbw_part, props);
 
 		props->bwa_wd = FIELD_GET(MPAMF_MBW_IDR_BWA_WD, mbw_features);
+
+		/*
+		 * The BWA_WD field can represent 0-63, but the control fields it
+		 * describes have a maximum of 16 bits.
+		 */
+		props->bwa_wd = min(props->bwa_wd, 16);
+
 		if (props->bwa_wd && FIELD_GET(MPAMF_MBW_IDR_HAS_MAX, mbw_features))
 			mpam_set_feature(mpam_feat_mbw_max, props);
 
@@ -1387,8 +1394,12 @@ static void mpam_reprogram_ris_partid(struct mpam_msc_ris *ris, u16 partid,
 	}
 
 	if (mpam_has_feature(mpam_feat_mbw_min, rprops) &&
-	    mpam_has_feature(mpam_feat_mbw_min, cfg))
-		mpam_write_partsel_reg(msc, MBW_MIN, 0);
+	    mpam_has_feature(mpam_feat_mbw_min, cfg)) {
+		if (cfg->reset_mbw_min)
+			mpam_write_partsel_reg(msc, MBW_MIN, 0);
+		else
+			mpam_write_partsel_reg(msc, MBW_MIN, cfg->mbw_min);
+	}
 
 	if (mpam_has_feature(mpam_feat_mbw_max, rprops) &&
 	    mpam_has_feature(mpam_feat_mbw_max, cfg)) {
@@ -1503,6 +1514,7 @@ static void mpam_init_reset_cfg(struct mpam_config *reset_cfg)
 		.reset_cpbm = true,
 		.reset_mbw_pbm = true,
 		.reset_mbw_max = true,
+		.reset_mbw_min = true,
 	};
 	bitmap_fill(reset_cfg->features, MPAM_FEATURE_LAST);
 }
@@ -2401,6 +2413,45 @@ static void __destroy_component_cfg(struct mpam_component *comp)
 	}
 }
 
+static void mpam_extend_config(struct mpam_class *class, struct mpam_config *cfg)
+{
+	struct mpam_props *cprops = &class->props;
+	u16 min, min_hw_granule, delta;
+	u16 max_hw_value, res0_bits;
+
+	/*
+	 * MAX and MIN should be set together. If only one is provided,
+	 * generate a configuration for the other. If only one control
+	 * type is supported, the other value will be ignored.
+	 *
+	 * Resctrl can only configure the MAX.
+	 */
+	if (mpam_has_feature(mpam_feat_mbw_max, cfg) &&
+	    !mpam_has_feature(mpam_feat_mbw_min, cfg)) {
+		/*
+		 * Calculate the values the 'min' control can hold.
+		 * e.g. on a platform with bwa_wd = 8, min_hw_granule is 0x00ff
+		 * because those bits are RES0. Configurations of this value
+		 * are effectively zero. But configurations need to saturate
+		 * at min_hw_granule on systems with mismatched bwa_wd, where
+		 * the 'less than 0' values are implemented on some MSC, but
+		 * not others.
+		 */
+		res0_bits = 16 - cprops->bwa_wd;
+		max_hw_value = ((1 << cprops->bwa_wd) - 1) << res0_bits;
+		min_hw_granule = ~max_hw_value;
+
+		delta = ((5 * MPAMCFG_MBW_MAX_MAX) / 100) - 1;
+		if (cfg->mbw_max > delta)
+			min = cfg->mbw_max - delta;
+		else
+			min = 0;
+
+		cfg->mbw_min = max(min, min_hw_granule);
+		mpam_set_feature(mpam_feat_mbw_min, cfg);
+	}
+}
+
 static void mpam_reset_component_cfg(struct mpam_component *comp)
 {
 	int i;
@@ -2419,6 +2470,8 @@ static void mpam_reset_component_cfg(struct mpam_component *comp)
 			comp->cfg[i].mbw_pbm = GENMASK(cprops->mbw_pbm_bits - 1, 0);
 		if (cprops->bwa_wd)
 			comp->cfg[i].mbw_max = GENMASK(15, 16 - cprops->bwa_wd);
+
+		mpam_extend_config(comp->class, &comp->cfg[i]);
 	}
 }
 
@@ -2694,24 +2747,37 @@ static bool mpam_update_config(struct mpam_config *cfg,
 	maybe_update_config(cfg, mpam_feat_cpor_part, newcfg, cpbm, has_changes);
 	maybe_update_config(cfg, mpam_feat_mbw_part, newcfg, mbw_pbm, has_changes);
 	maybe_update_config(cfg, mpam_feat_mbw_max, newcfg, mbw_max, has_changes);
+	maybe_update_config(cfg, mpam_feat_mbw_min, newcfg, mbw_min, has_changes);
 
 	return has_changes;
 }
 
 int mpam_apply_config(struct mpam_component *comp, u16 partid,
-		      struct mpam_config *cfg)
+		      struct mpam_config *user_cfg)
 {
 	struct mpam_write_config_arg arg;
 	struct mpam_msc_ris *ris;
+	struct mpam_config cfg;
 	struct mpam_vmsc *vmsc;
 	struct mpam_msc *msc;
 
 	lockdep_assert_cpus_held();
 
 	/* Don't pass in the current config! */
-	WARN_ON_ONCE(&comp->cfg[partid] == cfg);
+	WARN_ON_ONCE(&comp->cfg[partid] == user_cfg);
+
+	/*
+	 * Copy the config to avoid writing back the 'extended' version to
+	 * the caller.
+	 * This avoids mpam_devices.c setting a mbm_min that mpam_resctrl.c
+	 * is unaware of ... when it then changes mbm_max to be lower than
+	 * mbm_min.
+	 */
+	cfg = *user_cfg;
+
+	mpam_extend_config(comp->class, &cfg);
 
-	if (!mpam_update_config(&comp->cfg[partid], cfg))
+	if (!mpam_update_config(&comp->cfg[partid], &cfg))
 		return 0;
 
 	arg.comp = comp;
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index 9a3996decda5..cc580dea9430 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -274,10 +274,12 @@ struct mpam_config {
 	u32	cpbm;
 	u32	mbw_pbm;
 	u16	mbw_max;
+	u16	mbw_min;
 
 	bool	reset_cpbm;
 	bool	reset_mbw_pbm;
 	bool	reset_mbw_max;
+	bool	reset_mbw_min;
 
 	struct mpam_garbage	garbage;
 };
@@ -615,6 +617,7 @@ static inline void mpam_resctrl_teardown_class(struct mpam_class *class) { }
  * MPAMCFG_MBW_MAX - MPAM memory maximum bandwidth partitioning configuration
  *                   register
  */
+#define MPAMCFG_MBW_MAX_MAX_NR_BITS	16
 #define MPAMCFG_MBW_MAX_MAX		GENMASK(15, 0)
 #define MPAMCFG_MBW_MAX_HARDLIM		BIT(31)
 
diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index bbb12b5dfd8c..b24ae75ec6f0 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -1447,6 +1447,8 @@ int resctrl_arch_update_one(struct rdt_resource *r, struct rdt_ctrl_domain *d,
 		if (mpam_has_feature(mpam_feat_mbw_max, cprops)) {
 			cfg.mbw_max = percent_to_mbw_max(cfg_val, cprops);
 			mpam_set_feature(mpam_feat_mbw_max, &cfg);
+			/* Allow the min to be calculated from the max */
+			mpam_clear_feature(mpam_feat_mbw_min, &cfg);
 			break;
 		}
 		fallthrough;
diff --git a/drivers/resctrl/test_mpam_devices.c b/drivers/resctrl/test_mpam_devices.c
index 3e8d564a0c64..2f802fd9f249 100644
--- a/drivers/resctrl/test_mpam_devices.c
+++ b/drivers/resctrl/test_mpam_devices.c
@@ -322,6 +322,71 @@ static void test_mpam_enable_merge_features(struct kunit *test)
 	mutex_unlock(&mpam_list_lock);
 }
 
+static void test_mpam_extend_config(struct kunit *test)
+{
+	struct mpam_config fake_cfg = { };
+	struct mpam_class fake_class = { };
+
+	/* Configurations with both are not modified */
+	fake_class.props.bwa_wd = 16;
+	fake_cfg.mbw_max = 0xfeef;
+	fake_cfg.mbw_min = 0xfeef;
+	bitmap_zero(fake_cfg.features, MPAM_FEATURE_LAST);
+	mpam_set_feature(mpam_feat_mbw_max, &fake_cfg);
+	mpam_set_feature(mpam_feat_mbw_min, &fake_cfg);
+	mpam_extend_config(&fake_class, &fake_cfg);
+	KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_max, &fake_cfg));
+	KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_min, &fake_cfg));
+	KUNIT_EXPECT_EQ(test, fake_cfg.mbw_max, 0xfeef);
+	KUNIT_EXPECT_EQ(test, fake_cfg.mbw_min, 0xfeef);
+
+	/* When a min is missing, it is generated */
+	fake_class.props.bwa_wd = 16;
+	fake_cfg.mbw_max = 0xfeef;
+	fake_cfg.mbw_min = 0;
+	bitmap_zero(fake_cfg.features, MPAM_FEATURE_LAST);
+	mpam_set_feature(mpam_feat_mbw_max, &fake_cfg);
+	mpam_extend_config(&fake_class, &fake_cfg);
+	KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_max, &fake_cfg));
+	KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_min, &fake_cfg));
+	KUNIT_EXPECT_EQ(test, fake_cfg.mbw_max, 0xfeef);
+	KUNIT_EXPECT_EQ(test, fake_cfg.mbw_min, 0xf224);
+
+	fake_class.props.bwa_wd = 8;
+	fake_cfg.mbw_max = 0xfeef;
+	fake_cfg.mbw_min = 0;
+	bitmap_zero(fake_cfg.features, MPAM_FEATURE_LAST);
+	mpam_set_feature(mpam_feat_mbw_max, &fake_cfg);
+	mpam_extend_config(&fake_class, &fake_cfg);
+	KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_max, &fake_cfg));
+	KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_min, &fake_cfg));
+	KUNIT_EXPECT_EQ(test, fake_cfg.mbw_max, 0xfeef);
+	KUNIT_EXPECT_EQ(test, fake_cfg.mbw_min, 0xf224);
+
+	/* 5% below the minimum granule, is still the minimum granule */
+	fake_class.props.bwa_wd = 12;
+	fake_cfg.mbw_max = 0xf;
+	fake_cfg.mbw_min = 0;
+	bitmap_zero(fake_cfg.features, MPAM_FEATURE_LAST);
+	mpam_set_feature(mpam_feat_mbw_max, &fake_cfg);
+	mpam_extend_config(&fake_class, &fake_cfg);
+	KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_max, &fake_cfg));
+	KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_min, &fake_cfg));
+	KUNIT_EXPECT_EQ(test, fake_cfg.mbw_max, 0xf);
+	KUNIT_EXPECT_EQ(test, fake_cfg.mbw_min, 0xf);
+
+	fake_class.props.bwa_wd = 16;
+	fake_cfg.mbw_max = 0x4;
+	fake_cfg.mbw_min = 0;
+	bitmap_zero(fake_cfg.features, MPAM_FEATURE_LAST);
+	mpam_set_feature(mpam_feat_mbw_max, &fake_cfg);
+	mpam_extend_config(&fake_class, &fake_cfg);
+	KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_max, &fake_cfg));
+	KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_min, &fake_cfg));
+	KUNIT_EXPECT_EQ(test, fake_cfg.mbw_max, 0x4);
+	KUNIT_EXPECT_EQ(test, fake_cfg.mbw_min, 0x0);
+}
+
 static void test_mpam_reset_msc_bitmap(struct kunit *test)
 {
 	char __iomem *buf = kunit_kzalloc(test, SZ_16K, GFP_KERNEL);
@@ -378,6 +443,7 @@ static struct kunit_case mpam_devices_test_cases[] = {
 	KUNIT_CASE(test_mpam_reset_msc_bitmap),
 	KUNIT_CASE(test_mpam_enable_merge_features),
 	KUNIT_CASE(test__props_mismatch),
+	KUNIT_CASE(test_mpam_extend_config),
 	{}
 };
 
-- 
2.43.0

Re: [PATCH v2 40/45] arm_mpam: Generate a configuration for min controls

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:42 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> MPAM supports a minimum and maximum control for memory bandwidth. The
> purpose of the minimum control is to give priority to tasks that are below
> their minimum value. Resctrl only provides one value for the bandwidth
> configuration, which is used for the maximum.
> 
> The minimum control is always programmed to zero on hardware that supports
> it.
> 
> Generate a minimum bandwidth value that is 5% lower than the value provided
> by resctrl. This means tasks that are not receiving their target bandwidth
> can be prioritised by the hardware.

I'm not sure this policy make sense in general as there will be bandwidth
heavy background tasks where we want to make sure they only use up to X%
of bandwidth, but don't care if they don't get that.  I guess maybe those
are always in the %5 or less category so maybe this policy is fine.
Ah well, can revisit later I guess as long as we keep this as the default
for any new controls.

> 
> For component reset reuse the same calculation so that the default is a
> value resctrl can set.
> 
> CC: Zeng Heng <zengheng4@huawei.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>

Most, maybe all the other cases have split test from implementation. I'd
probably do that here just for consistency.

A few things inline.

J



> ---
> Add reset_mbw_min
> Clear min cfg when setting max
> use mpam_extend_config on component reset
> ---
>  drivers/resctrl/mpam_devices.c      | 76 +++++++++++++++++++++++++++--
>  drivers/resctrl/mpam_internal.h     |  3 ++
>  drivers/resctrl/mpam_resctrl.c      |  2 +
>  drivers/resctrl/test_mpam_devices.c | 66 +++++++++++++++++++++++++
>  4 files changed, 142 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> index c20b2757b86b..deea46c2a6c3 100644
> --- a/drivers/resctrl/mpam_devices.c
> +++ b/drivers/resctrl/mpam_devices.c
> @@ -721,6 +721,13 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
>  			mpam_set_feature(mpam_feat_mbw_part, props);
>  
>  		props->bwa_wd = FIELD_GET(MPAMF_MBW_IDR_BWA_WD, mbw_features);
> +
> +		/*
> +		 * The BWA_WD field can represent 0-63, but the control fields it
> +		 * describes have a maximum of 16 bits.

I'm lost to why this only matters now!  Feels like that makes sense way earlier
in the series. Particularly as that detail confused me no end in the bandwidth
/ percent calculation patches.

> +		 */
> +		props->bwa_wd = min(props->bwa_wd, 16);
> +
>  		if (props->bwa_wd && FIELD_GET(MPAMF_MBW_IDR_HAS_MAX, mbw_features))
>  			mpam_set_feature(mpam_feat_mbw_max, props);
>  

> +static void mpam_extend_config(struct mpam_class *class, struct mpam_config *cfg)
> +{
> +	struct mpam_props *cprops = &class->props;
> +	u16 min, min_hw_granule, delta;
> +	u16 max_hw_value, res0_bits;

Probably makes sense to drag some of these into the scope below.

> +
> +	/*
> +	 * MAX and MIN should be set together. If only one is provided,
> +	 * generate a configuration for the other. If only one control
> +	 * type is supported, the other value will be ignored.
> +	 *
> +	 * Resctrl can only configure the MAX.
> +	 */
> +	if (mpam_has_feature(mpam_feat_mbw_max, cfg) &&
> +	    !mpam_has_feature(mpam_feat_mbw_min, cfg)) {
> +		/*
> +		 * Calculate the values the 'min' control can hold.
> +		 * e.g. on a platform with bwa_wd = 8, min_hw_granule is 0x00ff
> +		 * because those bits are RES0. Configurations of this value
> +		 * are effectively zero. But configurations need to saturate
> +		 * at min_hw_granule on systems with mismatched bwa_wd, where
> +		 * the 'less than 0' values are implemented on some MSC, but
> +		 * not others.
> +		 */
> +		res0_bits = 16 - cprops->bwa_wd;
> +		max_hw_value = ((1 << cprops->bwa_wd) - 1) << res0_bits;
> +		min_hw_granule = ~max_hw_value;
> +
> +		delta = ((5 * MPAMCFG_MBW_MAX_MAX) / 100) - 1;
> +		if (cfg->mbw_max > delta)
> +			min = cfg->mbw_max - delta;
> +		else
> +			min = 0;
> +
> +		cfg->mbw_min = max(min, min_hw_granule);
> +		mpam_set_feature(mpam_feat_mbw_min, cfg);
> +	}
> +}
> +
>

[PATCH v2 41/45] arm_mpam: Add quirk framework

[Ben Horgan]

From: Shanker Donthineni <sdonthineni@nvidia.com>

The MPAM specification includes the MPAMF_IIDR, which serves to uniquely
identify the MSC implementation through a combination of implementer
details, product ID, variant, and revision. Certain hardware issues/errata
can be resolved using software workarounds.

Introduce a quirk framework to allow workarounds to be enabled based on the
MPAMF_IIDR value.

[ morse: Stash the IIDR so this doesn't need an IPI, enable quirks only
once, move the description to the callback so it can be pr_once()d, add an
enum of workarounds for popular errata. Add macros for making lists of
product/revision/vendor half readable ]

Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Changes since rfc:
remove trailing commas in last element of enums
Make mpam_enable_quirks() in charge of mpam_set_quirk() even if there
is an enable.
---
 drivers/resctrl/mpam_devices.c  | 32 ++++++++++++++++++++++++++++++++
 drivers/resctrl/mpam_internal.h | 25 +++++++++++++++++++++++++
 2 files changed, 57 insertions(+)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index deea46c2a6c3..1c574b5710d8 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -630,6 +630,30 @@ static struct mpam_msc_ris *mpam_get_or_create_ris(struct mpam_msc *msc,
 	return ERR_PTR(-ENOENT);
 }
 
+static const struct mpam_quirk mpam_quirks[] = {
+	{ NULL } /* Sentinel */
+};
+
+static void mpam_enable_quirks(struct mpam_msc *msc)
+{
+	const struct mpam_quirk *quirk;
+
+	for (quirk = &mpam_quirks[0]; quirk->iidr_mask; quirk++) {
+		int err = 0;
+
+		if (quirk->iidr != (msc->iidr & quirk->iidr_mask))
+			continue;
+
+		if (quirk->init)
+			err = quirk->init(msc, quirk);
+
+		if (err)
+			continue;
+
+		mpam_set_quirk(quirk->workaround, msc);
+	}
+}
+
 /*
  * IHI009A.a has this nugget: "If a monitor does not support automatic behaviour
  * of NRDY, software can use this bit for any purpose" - so hardware might not
@@ -864,8 +888,11 @@ static int mpam_msc_hw_probe(struct mpam_msc *msc)
 	/* Grab an IDR value to find out how many RIS there are */
 	mutex_lock(&msc->part_sel_lock);
 	idr = mpam_msc_read_idr(msc);
+	msc->iidr = mpam_read_partsel_reg(msc, IIDR);
 	mutex_unlock(&msc->part_sel_lock);
 
+	mpam_enable_quirks(msc);
+
 	msc->ris_max = FIELD_GET(MPAMF_IDR_RIS_MAX, idr);
 
 	/* Use these values so partid/pmg always starts with a valid value */
@@ -1993,6 +2020,7 @@ static bool mpam_has_cmax_wd_feature(struct mpam_props *props)
  * resulting safe value must be compatible with both. When merging values in
  * the tree, all the aliasing resources must be handled first.
  * On mismatch, parent is modified.
+ * Quirks on an MSC will apply to all MSC in that class.
  */
 static void __props_mismatch(struct mpam_props *parent,
 			     struct mpam_props *child, bool alias)
@@ -2112,6 +2140,7 @@ static void __props_mismatch(struct mpam_props *parent,
  * nobble the class feature, as we can't configure all the resources.
  * e.g. The L3 cache is composed of two resources with 13 and 17 portion
  * bitmaps respectively.
+ * Quirks on an MSC will apply to all MSC in that class.
  */
 static void
 __class_props_mismatch(struct mpam_class *class, struct mpam_vmsc *vmsc)
@@ -2125,6 +2154,9 @@ __class_props_mismatch(struct mpam_class *class, struct mpam_vmsc *vmsc)
 	dev_dbg(dev, "Merging features for class:0x%lx &= vmsc:0x%lx\n",
 		(long)cprops->features, (long)vprops->features);
 
+	/* Merge quirks */
+	class->quirks |= vmsc->msc->quirks;
+
 	/* Take the safe value for any common features */
 	__props_mismatch(cprops, vprops, false);
 }
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index cc580dea9430..5989f3670af3 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -85,6 +85,8 @@ struct mpam_msc {
 	u8			pmg_max;
 	unsigned long		ris_idxs;
 	u32			ris_max;
+	u32			iidr;
+	u16			quirks;
 
 	/*
 	 * error_irq_lock is taken when registering/unregistering the error
@@ -212,6 +214,28 @@ struct mpam_props {
 #define mpam_set_feature(_feat, x)	__set_bit(_feat, (x)->features)
 #define mpam_clear_feature(_feat, x)	__clear_bit(_feat, (x)->features)
 
+/* Workaround bits for msc->quirks */
+enum mpam_device_quirks {
+	MPAM_QUIRK_LAST
+};
+
+#define mpam_has_quirk(_quirk, x)	((1 << (_quirk) & (x)->quirks))
+#define mpam_set_quirk(_quirk, x)	((x)->quirks |= (1 << (_quirk)))
+
+struct mpam_quirk {
+	int (*init)(struct mpam_msc *msc, const struct mpam_quirk *quirk);
+
+	u32 iidr;
+	u32 iidr_mask;
+
+	enum mpam_device_quirks workaround;
+};
+
+#define MPAM_IIDR_MATCH_ONE	FIELD_PREP_CONST(MPAMF_IIDR_PRODUCTID,   0xfff)	| \
+				FIELD_PREP_CONST(MPAMF_IIDR_VARIANT,     0xf)	| \
+				FIELD_PREP_CONST(MPAMF_IIDR_REVISION,    0xf)	| \
+				FIELD_PREP_CONST(MPAMF_IIDR_IMPLEMENTER, 0xfff)
+
 /* The values for MSMON_CFG_MBWU_FLT.RWBW */
 enum mon_filter_options {
 	COUNT_BOTH	= 0,
@@ -255,6 +279,7 @@ struct mpam_class {
 
 	struct mpam_props	props;
 	u32			nrdy_usec;
+	u16			quirks;
 	u8			level;
 	enum mpam_class_types	type;
 
-- 
2.43.0

Re: [PATCH v2 41/45] arm_mpam: Add quirk framework

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:43 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: Shanker Donthineni <sdonthineni@nvidia.com>
> 
> The MPAM specification includes the MPAMF_IIDR, which serves to uniquely
> identify the MSC implementation through a combination of implementer
> details, product ID, variant, and revision. Certain hardware issues/errata
> can be resolved using software workarounds.
> 
> Introduce a quirk framework to allow workarounds to be enabled based on the
> MPAMF_IIDR value.
> 
> [ morse: Stash the IIDR so this doesn't need an IPI, enable quirks only
> once, move the description to the callback so it can be pr_once()d, add an
> enum of workarounds for popular errata. Add macros for making lists of
> product/revision/vendor half readable ]

Review comment that got left over? 

Otherwise looks fairly standard for quirk handling.
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> 
> Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>

Re: [PATCH v2 41/45] arm_mpam: Add quirk framework

[Jonathan Cameron]

On Tue, 6 Jan 2026 15:14:15 +0000
Jonathan Cameron <jonathan.cameron@huawei.com> wrote:

> On Fri, 19 Dec 2025 18:11:43 +0000
> Ben Horgan <ben.horgan@arm.com> wrote:
> 
> > From: Shanker Donthineni <sdonthineni@nvidia.com>
> > 
> > The MPAM specification includes the MPAMF_IIDR, which serves to uniquely
> > identify the MSC implementation through a combination of implementer
> > details, product ID, variant, and revision. Certain hardware issues/errata
> > can be resolved using software workarounds.
> > 
> > Introduce a quirk framework to allow workarounds to be enabled based on the
> > MPAMF_IIDR value.
> > 
> > [ morse: Stash the IIDR so this doesn't need an IPI, enable quirks only
> > once, move the description to the callback so it can be pr_once()d, add an
> > enum of workarounds for popular errata. Add macros for making lists of
> > product/revision/vendor half readable ]  
> 
> Review comment that got left over? 
Ah. I see, it's just change log for what James did.  Seem enough to add
a co-developed to me and maybe just leave this info under the ---?
> 
> Otherwise looks fairly standard for quirk handling.
> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
> 
> > 
> > Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com>
> > Signed-off-by: James Morse <james.morse@arm.com>
> > Signed-off-by: Ben Horgan <ben.horgan@arm.com>  
> 

[PATCH v2 42/45] arm_mpam: Add workaround for T241-MPAM-1

[Ben Horgan]

From: Shanker Donthineni <sdonthineni@nvidia.com>

The MPAM bandwidth partitioning controls will not be correctly configured,
and hardware will retain default configuration register values, meaning
generally that bandwidth will remain unprovisioned.

To address the issue, follow the below steps after updating the MBW_MIN
and/or MBW_MAX registers.

 - Perform 64b reads from all 12 bridge MPAM shadow registers at offsets
   (0x360048 + slice*0x10000 + partid*8). These registers are read-only.
 - Continue iterating until all 12 shadow register values match in a loop.
   pr_warn_once if the values fail to match within the loop count 1000.
 - Perform 64b writes with the value 0x0 to the two spare registers at
   offsets 0x1b0000 and 0x1c0000.

In the hardware, writes to the MPAMCFG_MBW_MAX MPAMCFG_MBW_MIN registers
are transformed into broadcast writes to the 12 shadow registers. The
final two writes to the spare registers cause a final rank of downstream
micro-architectural MPAM registers to be updated from the shadow copies.
The intervening loop to read the 12 shadow registers helps avoid a race
condition where writes to the spare registers occur before all shadow
registers have been updated.

[ morse: Merged the min/max update into a single
  mpam_quirk_post_config_change() helper. Stashed the t241_id in the msc
  instead of carrying the physical address around. Test the msc quirk bit
  instead of a static key. ]

Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Changes since rfc:
MPAM_IIDR_NVIDIA_T421 -> MPAM_IIDR_NVIDIA_T241
return err from init
Be specific about the errata in the init name,
  mpam_enable_quirk_nvidia_t241 -> mpam_enable_quirk_nvidia_t241_1
---
 Documentation/arch/arm64/silicon-errata.rst |  2 +
 drivers/resctrl/mpam_devices.c              | 88 +++++++++++++++++++++
 drivers/resctrl/mpam_internal.h             |  9 +++
 3 files changed, 99 insertions(+)

diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst
index a7ec57060f64..4e86b85fe3d6 100644
--- a/Documentation/arch/arm64/silicon-errata.rst
+++ b/Documentation/arch/arm64/silicon-errata.rst
@@ -246,6 +246,8 @@ stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | NVIDIA         | T241 GICv3/4.x  | T241-FABRIC-4   | N/A                         |
 +----------------+-----------------+-----------------+-----------------------------+
+| NVIDIA         | T241 MPAM       | T241-MPAM-1     | N/A                         |
++----------------+-----------------+-----------------+-----------------------------+
 +----------------+-----------------+-----------------+-----------------------------+
 | Freescale/NXP  | LS2080A/LS1043A | A-008585        | FSL_ERRATUM_A008585         |
 +----------------+-----------------+-----------------+-----------------------------+
diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 1c574b5710d8..1b923a44f304 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -29,6 +29,16 @@
 
 #include "mpam_internal.h"
 
+/* Values for the T241 errata workaround */
+#define T241_CHIPS_MAX			4
+#define T241_CHIP_NSLICES		12
+#define T241_SPARE_REG0_OFF		0x1b0000
+#define T241_SPARE_REG1_OFF		0x1c0000
+#define T241_CHIP_ID(phys)		FIELD_GET(GENMASK_ULL(44, 43), phys)
+#define T241_SHADOW_REG_OFF(sidx, pid)	(0x360048 + (sidx) * 0x10000 + (pid) * 8)
+#define SMCCC_SOC_ID_T241		0x036b0241
+static void __iomem *t241_scratch_regs[T241_CHIPS_MAX];
+
 /*
  * mpam_list_lock protects the SRCU lists when writing. Once the
  * mpam_enabled key is enabled these lists are read-only,
@@ -630,7 +640,45 @@ static struct mpam_msc_ris *mpam_get_or_create_ris(struct mpam_msc *msc,
 	return ERR_PTR(-ENOENT);
 }
 
+static int mpam_enable_quirk_nvidia_t241_1(struct mpam_msc *msc,
+					  const struct mpam_quirk *quirk)
+{
+	s32 soc_id = arm_smccc_get_soc_id_version();
+	struct resource *r;
+	phys_addr_t phys;
+
+	/*
+	 * A mapping to a device other than the MSC is needed, check
+	 * SOC_ID is  NVIDIA T241 chip (036b:0241)
+	 */
+	if (soc_id < 0 || soc_id != SMCCC_SOC_ID_T241)
+		return -EINVAL;
+
+	r = platform_get_resource(msc->pdev, IORESOURCE_MEM, 0);
+	if (!r)
+		return -EINVAL;
+
+	/* Find the internal registers base addr from the CHIP ID */
+	msc->t241_id = T241_CHIP_ID(r->start);
+	phys = FIELD_PREP(GENMASK_ULL(45, 44), msc->t241_id) | 0x19000000ULL;
+
+	t241_scratch_regs[msc->t241_id] = ioremap(phys, SZ_8M);
+	if (WARN_ON_ONCE(!t241_scratch_regs[msc->t241_id]))
+		return -EINVAL;
+
+	pr_info_once("Enabled workaround for NVIDIA T241 erratum T241-MPAM-1\n");
+
+	return 0;
+}
+
 static const struct mpam_quirk mpam_quirks[] = {
+	{
+	/* NVIDIA t241 erratum T241-MPAM-1 */
+	.init       = mpam_enable_quirk_nvidia_t241_1,
+	.iidr       = MPAM_IIDR_NVIDIA_T241,
+	.iidr_mask  = MPAM_IIDR_MATCH_ONE,
+	.workaround = T241_SCRUB_SHADOW_REGS,
+	},
 	{ NULL } /* Sentinel */
 };
 
@@ -1378,6 +1426,44 @@ static void mpam_reset_msc_bitmap(struct mpam_msc *msc, u16 reg, u16 wd)
 	__mpam_write_reg(msc, reg, bm);
 }
 
+static void mpam_apply_t241_erratum(struct mpam_msc_ris *ris, u16 partid)
+{
+	int sidx, i, lcount = 1000;
+	void __iomem *regs;
+	u64 val0, val;
+
+	regs = t241_scratch_regs[ris->vmsc->msc->t241_id];
+
+	for (i = 0; i < lcount; i++) {
+		/* Read the shadow register at index 0 */
+		val0 = readq_relaxed(regs + T241_SHADOW_REG_OFF(0, partid));
+
+		/* Check if all the shadow registers have the same value */
+		for (sidx = 1; sidx < T241_CHIP_NSLICES; sidx++) {
+			val = readq_relaxed(regs +
+					    T241_SHADOW_REG_OFF(sidx, partid));
+			if (val != val0)
+				break;
+		}
+		if (sidx == T241_CHIP_NSLICES)
+			break;
+	}
+
+	if (i == lcount)
+		pr_warn_once("t241: inconsistent values in shadow regs");
+
+	/* Write a value zero to spare registers to take effect of MBW conf */
+	writeq_relaxed(0, regs + T241_SPARE_REG0_OFF);
+	writeq_relaxed(0, regs + T241_SPARE_REG1_OFF);
+}
+
+static void mpam_quirk_post_config_change(struct mpam_msc_ris *ris, u16 partid,
+					  struct mpam_config *cfg)
+{
+	if (mpam_has_quirk(T241_SCRUB_SHADOW_REGS, ris->vmsc->msc))
+		mpam_apply_t241_erratum(ris, partid);
+}
+
 /* Called via IPI. Call while holding an SRCU reference */
 static void mpam_reprogram_ris_partid(struct mpam_msc_ris *ris, u16 partid,
 				      struct mpam_config *cfg)
@@ -1465,6 +1551,8 @@ static void mpam_reprogram_ris_partid(struct mpam_msc_ris *ris, u16 partid,
 		mpam_write_partsel_reg(msc, PRI, pri_val);
 	}
 
+	mpam_quirk_post_config_change(ris, partid, cfg);
+
 	mutex_unlock(&msc->part_sel_lock);
 }
 
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index 5989f3670af3..871ca2169173 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -130,6 +130,9 @@ struct mpam_msc {
 	void __iomem		*mapped_hwpage;
 	size_t			mapped_hwpage_sz;
 
+	/* Values only used on some platforms for quirks */
+	u32			t241_id;
+
 	struct mpam_garbage	garbage;
 };
 
@@ -216,6 +219,7 @@ struct mpam_props {
 
 /* Workaround bits for msc->quirks */
 enum mpam_device_quirks {
+	T241_SCRUB_SHADOW_REGS,
 	MPAM_QUIRK_LAST
 };
 
@@ -236,6 +240,11 @@ struct mpam_quirk {
 				FIELD_PREP_CONST(MPAMF_IIDR_REVISION,    0xf)	| \
 				FIELD_PREP_CONST(MPAMF_IIDR_IMPLEMENTER, 0xfff)
 
+#define MPAM_IIDR_NVIDIA_T241	FIELD_PREP_CONST(MPAMF_IIDR_PRODUCTID,   0x241)	| \
+				FIELD_PREP_CONST(MPAMF_IIDR_VARIANT,     0)	| \
+				FIELD_PREP_CONST(MPAMF_IIDR_REVISION,    0)	| \
+				FIELD_PREP_CONST(MPAMF_IIDR_IMPLEMENTER, 0x36b)
+
 /* The values for MSMON_CFG_MBWU_FLT.RWBW */
 enum mon_filter_options {
 	COUNT_BOTH	= 0,
-- 
2.43.0

[PATCH v2 43/45] arm_mpam: Add workaround for T241-MPAM-4

[Ben Horgan]

From: Shanker Donthineni <sdonthineni@nvidia.com>

In the T241 implementation of memory-bandwidth partitioning, in the absence
of contention for bandwidth, the minimum bandwidth setting can affect the
amount of achieved bandwidth. Specifically, the achieved bandwidth in the
absence of contention can settle to any value between the values of
MPAMCFG_MBW_MIN and MPAMCFG_MBW_MAX.  Also, if MPAMCFG_MBW_MIN is set
zero (below 0.78125%), once a core enters a throttled state, it will never
leave that state.

The first issue is not a cocern if the MPAM software allows to program
MPAMCFG_MBW_MIN through the sysfs interface. This patch ensures program
MBW_MIN=1 (0.78125%) whenever MPAMCFG_MBW_MIN=0 is programmed.

In the scenario where the resctrl doesn't support the MBW_MIN interface via
sysfs, to achieve bandwidth closer to MW_MAX in the absence of contention,
software should configure a relatively narrow gap between MBW_MIN and
MBW_MAX. The recommendation is to use a 5% gap to mitigate the problem.

[ morse: Added as second quirk, adapted to use the new intermediate values
in mpam_extend_config() ]

Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Changes since rfc:
MPAM_IIDR_NVIDIA_T421 -> MPAM_IIDR_NVIDIA_T241
Handling when reset_mbw_min is set
---
 Documentation/arch/arm64/silicon-errata.rst |  2 +
 drivers/resctrl/mpam_devices.c              | 59 +++++++++++++++------
 drivers/resctrl/mpam_internal.h             |  1 +
 3 files changed, 46 insertions(+), 16 deletions(-)

diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst
index 4e86b85fe3d6..b18bc704d4a1 100644
--- a/Documentation/arch/arm64/silicon-errata.rst
+++ b/Documentation/arch/arm64/silicon-errata.rst
@@ -248,6 +248,8 @@ stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | NVIDIA         | T241 MPAM       | T241-MPAM-1     | N/A                         |
 +----------------+-----------------+-----------------+-----------------------------+
+| NVIDIA         | T241 MPAM       | T241-MPAM-4     | N/A                         |
++----------------+-----------------+-----------------+-----------------------------+
 +----------------+-----------------+-----------------+-----------------------------+
 | Freescale/NXP  | LS2080A/LS1043A | A-008585        | FSL_ERRATUM_A008585         |
 +----------------+-----------------+-----------------+-----------------------------+
diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 1b923a44f304..76aa8654fc74 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -679,6 +679,12 @@ static const struct mpam_quirk mpam_quirks[] = {
 	.iidr_mask  = MPAM_IIDR_MATCH_ONE,
 	.workaround = T241_SCRUB_SHADOW_REGS,
 	},
+	{
+	/* NVIDIA t241 erratum T241-MPAM-4 */
+	.iidr       = MPAM_IIDR_NVIDIA_T241,
+	.iidr_mask  = MPAM_IIDR_MATCH_ONE,
+	.workaround = T241_FORCE_MBW_MIN_TO_ONE,
+	},
 	{ NULL } /* Sentinel */
 };
 
@@ -1464,6 +1470,17 @@ static void mpam_quirk_post_config_change(struct mpam_msc_ris *ris, u16 partid,
 		mpam_apply_t241_erratum(ris, partid);
 }
 
+static u16 mpam_wa_t241_force_mbw_min_to_one(struct mpam_props *props)
+{
+	u16 max_hw_value, min_hw_granule, res0_bits;
+
+	res0_bits = 16 - props->bwa_wd;
+	max_hw_value = ((1 << props->bwa_wd) - 1) << res0_bits;
+	min_hw_granule = ~max_hw_value;
+
+	return min_hw_granule + 1;
+}
+
 /* Called via IPI. Call while holding an SRCU reference */
 static void mpam_reprogram_ris_partid(struct mpam_msc_ris *ris, u16 partid,
 				      struct mpam_config *cfg)
@@ -1508,10 +1525,15 @@ static void mpam_reprogram_ris_partid(struct mpam_msc_ris *ris, u16 partid,
 
 	if (mpam_has_feature(mpam_feat_mbw_min, rprops) &&
 	    mpam_has_feature(mpam_feat_mbw_min, cfg)) {
-		if (cfg->reset_mbw_min)
-			mpam_write_partsel_reg(msc, MBW_MIN, 0);
-		else
+		if (cfg->reset_mbw_min) {
+			u16 reset = 0;
+
+			if (mpam_has_quirk(T241_FORCE_MBW_MIN_TO_ONE, msc))
+				reset = mpam_wa_t241_force_mbw_min_to_one(rprops);
+			mpam_write_partsel_reg(msc, MBW_MIN, reset);
+		} else {
 			mpam_write_partsel_reg(msc, MBW_MIN, cfg->mbw_min);
+		}
 	}
 
 	if (mpam_has_feature(mpam_feat_mbw_max, rprops) &&
@@ -2539,6 +2561,18 @@ static void mpam_extend_config(struct mpam_class *class, struct mpam_config *cfg
 	u16 min, min_hw_granule, delta;
 	u16 max_hw_value, res0_bits;
 
+	/*
+	 * Calculate the values the 'min' control can hold.
+	 * e.g. on a platform with bwa_wd = 8, min_hw_granule is 0x00ff because
+	 * those bits are RES0. Configurations of this value are effectively
+	 * zero. But configurations need to saturate at min_hw_granule on
+	 * systems with mismatched bwa_wd, where the 'less than 0' values are
+	 * implemented on some MSC, but not others.
+	 */
+	res0_bits = 16 - cprops->bwa_wd;
+	max_hw_value = ((1 << cprops->bwa_wd) - 1) << res0_bits;
+	min_hw_granule = ~max_hw_value;
+
 	/*
 	 * MAX and MIN should be set together. If only one is provided,
 	 * generate a configuration for the other. If only one control
@@ -2548,19 +2582,6 @@ static void mpam_extend_config(struct mpam_class *class, struct mpam_config *cfg
 	 */
 	if (mpam_has_feature(mpam_feat_mbw_max, cfg) &&
 	    !mpam_has_feature(mpam_feat_mbw_min, cfg)) {
-		/*
-		 * Calculate the values the 'min' control can hold.
-		 * e.g. on a platform with bwa_wd = 8, min_hw_granule is 0x00ff
-		 * because those bits are RES0. Configurations of this value
-		 * are effectively zero. But configurations need to saturate
-		 * at min_hw_granule on systems with mismatched bwa_wd, where
-		 * the 'less than 0' values are implemented on some MSC, but
-		 * not others.
-		 */
-		res0_bits = 16 - cprops->bwa_wd;
-		max_hw_value = ((1 << cprops->bwa_wd) - 1) << res0_bits;
-		min_hw_granule = ~max_hw_value;
-
 		delta = ((5 * MPAMCFG_MBW_MAX_MAX) / 100) - 1;
 		if (cfg->mbw_max > delta)
 			min = cfg->mbw_max - delta;
@@ -2570,6 +2591,12 @@ static void mpam_extend_config(struct mpam_class *class, struct mpam_config *cfg
 		cfg->mbw_min = max(min, min_hw_granule);
 		mpam_set_feature(mpam_feat_mbw_min, cfg);
 	}
+
+	if (mpam_has_quirk(T241_FORCE_MBW_MIN_TO_ONE, class) &&
+	    cfg->mbw_min <= min_hw_granule) {
+		cfg->mbw_min = min_hw_granule + 1;
+		mpam_set_feature(mpam_feat_mbw_min, cfg);
+	}
 }
 
 static void mpam_reset_component_cfg(struct mpam_component *comp)
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index 871ca2169173..b4f2505519b2 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -220,6 +220,7 @@ struct mpam_props {
 /* Workaround bits for msc->quirks */
 enum mpam_device_quirks {
 	T241_SCRUB_SHADOW_REGS,
+	T241_FORCE_MBW_MIN_TO_ONE,
 	MPAM_QUIRK_LAST
 };
 
-- 
2.43.0

Re: [PATCH v2 43/45] arm_mpam: Add workaround for T241-MPAM-4

[Jonathan Cameron]

On Fri, 19 Dec 2025 18:11:45 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: Shanker Donthineni <sdonthineni@nvidia.com>
> 
> In the T241 implementation of memory-bandwidth partitioning, in the absence
> of contention for bandwidth, the minimum bandwidth setting can affect the
> amount of achieved bandwidth. Specifically, the achieved bandwidth in the
> absence of contention can settle to any value between the values of
> MPAMCFG_MBW_MIN and MPAMCFG_MBW_MAX.  Also, if MPAMCFG_MBW_MIN is set
> zero (below 0.78125%), once a core enters a throttled state, it will never
> leave that state.
> 
> The first issue is not a cocern if the MPAM software allows to program
concern

> MPAMCFG_MBW_MIN through the sysfs interface. This patch ensures program
> MBW_MIN=1 (0.78125%) whenever MPAMCFG_MBW_MIN=0 is programmed.
> 
> In the scenario where the resctrl doesn't support the MBW_MIN interface via
> sysfs, to achieve bandwidth closer to MW_MAX in the absence of contention,
MBW_MAX

> software should configure a relatively narrow gap between MBW_MIN and
> MBW_MAX. The recommendation is to use a 5% gap to mitigate the problem.
> 
> [ morse: Added as second quirk, adapted to use the new intermediate values
> in mpam_extend_config() ]
> 
> Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> ---
> Changes since rfc:
> MPAM_IIDR_NVIDIA_T421 -> MPAM_IIDR_NVIDIA_T241
> Handling when reset_mbw_min is set
> ---
>  Documentation/arch/arm64/silicon-errata.rst |  2 +
>  drivers/resctrl/mpam_devices.c              | 59 +++++++++++++++------
>  drivers/resctrl/mpam_internal.h             |  1 +
>  3 files changed, 46 insertions(+), 16 deletions(-)
> 
> diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst
> index 4e86b85fe3d6..b18bc704d4a1 100644
> --- a/Documentation/arch/arm64/silicon-errata.rst
> +++ b/Documentation/arch/arm64/silicon-errata.rst
> @@ -248,6 +248,8 @@ stable kernels.
>  +----------------+-----------------+-----------------+-----------------------------+
>  | NVIDIA         | T241 MPAM       | T241-MPAM-1     | N/A                         |
>  +----------------+-----------------+-----------------+-----------------------------+
> +| NVIDIA         | T241 MPAM       | T241-MPAM-4     | N/A                         |
> ++----------------+-----------------+-----------------+-----------------------------+
>  +----------------+-----------------+-----------------+-----------------------------+
>  | Freescale/NXP  | LS2080A/LS1043A | A-008585        | FSL_ERRATUM_A008585         |
>  +----------------+-----------------+-----------------+-----------------------------+

[PATCH v2 44/45] arm_mpam: Add workaround for T241-MPAM-6

[Ben Horgan]

From: Shanker Donthineni <sdonthineni@nvidia.com>

The registers MSMON_MBWU_L and MSMON_MBWU return the number of requests
rather than the number of bytes transferred.

Bandwidth resource monitoring is performed at the last level cache, where
each request arrive in 64Byte granularity. The current implementation
returns the number of transactions received at the last level cache but
does not provide the value in bytes. Scaling by 64 gives an accurate byte
count to match the MPAM specification for the MSMON_MBWU and MSMON_MBWU_L
registers. This patch fixes the issue by reporting the actual number of
bytes instead of the number of transactions from __ris_msmon_read().

Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Changes since rfc:
MPAM_IIDR_NVIDIA_T421 -> MPAM_IIDR_NVIDIA_T241
Don't apply workaround to MSMON_MBWU_LWD
---
 Documentation/arch/arm64/silicon-errata.rst |  2 ++
 drivers/resctrl/mpam_devices.c              | 26 +++++++++++++++++++--
 drivers/resctrl/mpam_internal.h             |  1 +
 3 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst
index b18bc704d4a1..e810b2a8f40e 100644
--- a/Documentation/arch/arm64/silicon-errata.rst
+++ b/Documentation/arch/arm64/silicon-errata.rst
@@ -250,6 +250,8 @@ stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | NVIDIA         | T241 MPAM       | T241-MPAM-4     | N/A                         |
 +----------------+-----------------+-----------------+-----------------------------+
+| NVIDIA         | T241 MPAM       | T241-MPAM-6     | N/A                         |
++----------------+-----------------+-----------------+-----------------------------+
 +----------------+-----------------+-----------------+-----------------------------+
 | Freescale/NXP  | LS2080A/LS1043A | A-008585        | FSL_ERRATUM_A008585         |
 +----------------+-----------------+-----------------+-----------------------------+
diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 76aa8654fc74..912736cd86b6 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -685,6 +685,12 @@ static const struct mpam_quirk mpam_quirks[] = {
 	.iidr_mask  = MPAM_IIDR_MATCH_ONE,
 	.workaround = T241_FORCE_MBW_MIN_TO_ONE,
 	},
+	{
+	/* NVIDIA t241 erratum T241-MPAM-6 */
+	.iidr       = MPAM_IIDR_NVIDIA_T241,
+	.iidr_mask  = MPAM_IIDR_MATCH_ONE,
+	.workaround = T241_MBW_COUNTER_SCALE_64,
+	},
 	{ NULL } /* Sentinel */
 };
 
@@ -1146,7 +1152,7 @@ static void write_msmon_ctl_flt_vals(struct mon_read *m, u32 ctl_val,
 	}
 }
 
-static u64 mpam_msmon_overflow_val(enum mpam_device_features type)
+static u64 __mpam_msmon_overflow_val(enum mpam_device_features type)
 {
 	/* TODO: implement scaling counters */
 	switch (type) {
@@ -1161,6 +1167,18 @@ static u64 mpam_msmon_overflow_val(enum mpam_device_features type)
 	}
 }
 
+static u64 mpam_msmon_overflow_val(enum mpam_device_features type,
+				   struct mpam_msc *msc)
+{
+	u64 overflow_val = __mpam_msmon_overflow_val(type);
+
+	if (mpam_has_quirk(T241_MBW_COUNTER_SCALE_64, msc) &&
+	    type != mpam_feat_msmon_mbwu_63counter)
+		overflow_val *= 64;
+
+	return overflow_val;
+}
+
 static void __ris_msmon_read(void *arg)
 {
 	u64 now;
@@ -1251,13 +1269,17 @@ static void __ris_msmon_read(void *arg)
 			now = FIELD_GET(MSMON___VALUE, now);
 		}
 
+		if (mpam_has_quirk(T241_MBW_COUNTER_SCALE_64, msc) &&
+		    m->type != mpam_feat_msmon_mbwu_63counter)
+			now *= 64;
+
 		if (nrdy)
 			break;
 
 		mbwu_state = &ris->mbwu_state[ctx->mon];
 
 		if (overflow)
-			mbwu_state->correction += mpam_msmon_overflow_val(m->type);
+			mbwu_state->correction += mpam_msmon_overflow_val(m->type, msc);
 
 		/*
 		 * Include bandwidth consumed before the last hardware reset and
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index b4f2505519b2..1e7574a9d244 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -221,6 +221,7 @@ struct mpam_props {
 enum mpam_device_quirks {
 	T241_SCRUB_SHADOW_REGS,
 	T241_FORCE_MBW_MIN_TO_ONE,
+	T241_MBW_COUNTER_SCALE_64,
 	MPAM_QUIRK_LAST
 };
 
-- 
2.43.0

[PATCH v2 45/45] arm_mpam: Quirk CMN-650's CSU NRDY behaviour

[Ben Horgan]

From: James Morse <james.morse@arm.com>

CMN-650 is afflicted with an erratum where the CSU NRDY bit never clears.
This tells us the monitor never finishes scanning the cache. The erratum
document says to wait the maximum time, then ignore the field.

Add a flag to indicate whether this is the final attempt to read the
counter, and when this quirk is applied, ignore the NRDY field.

This means accesses to this counter will always retry, even if the counter
was previously programmed to the same values.

The counter value is not expected to be stable, it drifts up and down with
each allocation and eviction. The CSU register provides the value for a
point in time.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
 Documentation/arch/arm64/silicon-errata.rst |  3 +++
 drivers/resctrl/mpam_devices.c              | 12 ++++++++++++
 drivers/resctrl/mpam_internal.h             |  6 ++++++
 3 files changed, 21 insertions(+)

diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst
index e810b2a8f40e..3667650036fb 100644
--- a/Documentation/arch/arm64/silicon-errata.rst
+++ b/Documentation/arch/arm64/silicon-errata.rst
@@ -213,6 +213,9 @@ stable kernels.
 | ARM            | GIC-700         | #2941627        | ARM64_ERRATUM_2941627       |
 +----------------+-----------------+-----------------+-----------------------------+
 +----------------+-----------------+-----------------+-----------------------------+
+| ARM            | CMN-650         | #3642720        | N/A                         |
++----------------+-----------------+-----------------+-----------------------------+
++----------------+-----------------+-----------------+-----------------------------+
 | Broadcom       | Brahma-B53      | N/A             | ARM64_ERRATUM_845719        |
 +----------------+-----------------+-----------------+-----------------------------+
 | Broadcom       | Brahma-B53      | N/A             | ARM64_ERRATUM_843419        |
diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 912736cd86b6..e0b27eb77fa7 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -691,6 +691,12 @@ static const struct mpam_quirk mpam_quirks[] = {
 	.iidr_mask  = MPAM_IIDR_MATCH_ONE,
 	.workaround = T241_MBW_COUNTER_SCALE_64,
 	},
+	{
+	/* ARM CMN-650 CSU erratum 3642720 */
+	.iidr       = MPAM_IIDR_ARM_CMN_650,
+	.iidr_mask  = MPAM_IIDR_MATCH_ONE,
+	.workaround = IGNORE_CSU_NRDY,
+	},
 	{ NULL } /* Sentinel */
 };
 
@@ -1003,6 +1009,7 @@ struct mon_read {
 	enum mpam_device_features	type;
 	u64				*val;
 	int				err;
+	bool				waited_timeout;
 };
 
 static bool mpam_ris_has_mbwu_long_counter(struct mpam_msc_ris *ris)
@@ -1249,6 +1256,10 @@ static void __ris_msmon_read(void *arg)
 		if (mpam_has_feature(mpam_feat_msmon_csu_hw_nrdy, rprops))
 			nrdy = now & MSMON___NRDY;
 		now = FIELD_GET(MSMON___VALUE, now);
+
+		if (mpam_has_quirk(IGNORE_CSU_NRDY, msc) && m->waited_timeout)
+			nrdy = false;
+
 		break;
 	case mpam_feat_msmon_mbwu_31counter:
 	case mpam_feat_msmon_mbwu_44counter:
@@ -1386,6 +1397,7 @@ int mpam_msmon_read(struct mpam_component *comp, struct mon_cfg *ctx,
 			.ctx = ctx,
 			.type = type,
 			.val = val,
+			.waited_timeout = true,
 		};
 		*val = 0;
 
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index 1e7574a9d244..e206decd3048 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -222,6 +222,7 @@ enum mpam_device_quirks {
 	T241_SCRUB_SHADOW_REGS,
 	T241_FORCE_MBW_MIN_TO_ONE,
 	T241_MBW_COUNTER_SCALE_64,
+	IGNORE_CSU_NRDY,
 	MPAM_QUIRK_LAST
 };
 
@@ -247,6 +248,11 @@ struct mpam_quirk {
 				FIELD_PREP_CONST(MPAMF_IIDR_REVISION,    0)	| \
 				FIELD_PREP_CONST(MPAMF_IIDR_IMPLEMENTER, 0x36b)
 
+#define MPAM_IIDR_ARM_CMN_650	FIELD_PREP_CONST(MPAMF_IIDR_PRODUCTID,   0)	| \
+				FIELD_PREP_CONST(MPAMF_IIDR_VARIANT,     0)	| \
+				FIELD_PREP_CONST(MPAMF_IIDR_REVISION,    0)	| \
+				FIELD_PREP_CONST(MPAMF_IIDR_IMPLEMENTER, 0x43b)
+
 /* The values for MSMON_CFG_MBWU_FLT.RWBW */
 enum mon_filter_options {
 	COUNT_BOTH	= 0,
-- 
2.43.0