[PATCH v3 00/47] arm_mpam: Add KVM/arm64 and resctrl glue code

Ben Horgan
2026-01-12T16:59:50Z

This new version of the mpam missing pieces has no major rework from the
previous version. It's mainly small corrections and code tidying based on
review and things I spotted along the way. To be able to merge this we need
review from more people and people to start testing on their platforms and
giving some Tested-by tags.

Change list in patches.

As mentioned in the cover letter for v2, 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. There are pros
and cons of choosing this policy but I think it is the best thing to start
with as there are AMD plans for adding a resctrl feature to allow a
different closid/rmid configuration for user-space from kernel space. The
AMD feature is called PLZA and is mentioned in this lpc slide deck[1]. This
gives us a path forward to add support for having the EL1 and EL0 MPAM
partid/pmg configuration differ from each other.

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-rc5
This series can be retrieved from:
https://gitlab.arm.com/linux-arm/linux-bh.git mpam_resctrl_glue_v3

v2 can be found at:
https://lore.kernel.org/linux-arm-kernel/20251219181147.3404071-1-ben.horgan@arm.com/

rfc can be found at:
https://lore.kernel.org/linux-arm-kernel/20251205215901.17772-1-james.morse@arm.com/

[1] https://lpc.events/event/19/contributions/2093/attachments/1958/4172/resctrl%20Microconference%20LPC%202025%20Tokyo.pdf

Ben Horgan (10):
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
arm_mpam: resctrl: Add rmid index helpers
arm_mpam: resctrl: Add kunit test for rmid idx conversions
arm_mpam: resctrl: Wait for cacheinfo to be ready
arm_mpam: resctrl: Add kunit test for mbw min control generation

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 (30):
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 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 | 98 +
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 | 8 +
arch/arm64/kvm/hyp/vhe/sysreg-sr.c | 13 +
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 | 306 ++-
drivers/resctrl/mpam_internal.h | 131 +-
drivers/resctrl/mpam_resctrl.c | 1930 +++++++++++++++++++
drivers/resctrl/test_mpam_devices.c | 66 +
drivers/resctrl/test_mpam_resctrl.c | 426 ++++
include/linux/arm_mpam.h | 32 +
23 files changed, 3119 insertions(+), 33 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

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2.43.0