* [PATCH v3 1/3] KVM: PPC: Book3S PR: Disable SCV when AIL could be disabled
2022-02-21 7:23 [PATCH v3 0/3] KVM: PPC: Book3S PR: Fixes for AIL and SCV Nicholas Piggin
@ 2022-02-21 7:23 ` Nicholas Piggin
2022-02-21 7:23 ` [PATCH v3 2/3] KVM: PPC: Book3S PR: Disallow AIL != 0 Nicholas Piggin
2022-02-21 7:23 ` [PATCH v3 3/3] KVM: PPC: Add KVM_CAP_PPC_AIL_MODE_3 Nicholas Piggin
2 siblings, 0 replies; 6+ messages in thread
From: Nicholas Piggin @ 2022-02-21 7:23 UTC (permalink / raw)
To: linuxppc-dev; +Cc: Nicholas Piggin, Fabiano Rosas
PR KVM does not support running with AIL enabled, and SCV does is not
supported with AIL disabled. Fix this by ensuring the SCV facility is
disabled with FSCR while a CPU could be running with AIL=0.
The PowerNV host supports disabling AIL on a per-CPU basis, so SCV just
needs to be disabled when a vCPU is being run.
The pSeries machine can only switch AIL on a system-wide basis, so it
must disable SCV support at boot if the configuration can potentially
run a PR KVM guest.
Also ensure a the FSCR[SCV] bit can not be enabled when emulating
mtFSCR for the guest.
SCV is not emulated for the PR guest at the moment, this just fixes the
host crashes.
Alternatives considered and rejected:
- SCV support can not be disabled by PR KVM after boot, because it is
advertised to userspace with HWCAP.
- AIL can not be disabled on a per-CPU basis. At least when running on
pseries it is a per-LPAR setting.
- Support for real-mode SCV vectors will not be added because they are
at 0x17000 so making such a large fixed head space causes immediate
value limits to be exceeded, requiring a lot rework and more code.
- Disabling SCV for any PR KVM possible kernel will cause a slowdown
when not using PR KVM.
- A boot time option to disable SCV to use PR KVM is user-hostile.
- System call instruction emulation for SCV facility unavailable
instructions is too complex and old emulation code was subtly broken
and removed.
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
arch/powerpc/kernel/exceptions-64s.S | 4 ++++
arch/powerpc/kernel/setup_64.c | 28 ++++++++++++++++++++++++++++
arch/powerpc/kvm/Kconfig | 9 +++++++++
arch/powerpc/kvm/book3s_pr.c | 26 +++++++++++++++++---------
4 files changed, 58 insertions(+), 9 deletions(-)
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 55caeee37c08..b66dd6f775a4 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -809,6 +809,10 @@ __start_interrupts:
* - MSR_EE|MSR_RI is clear (no reentrant exceptions)
* - Standard kernel environment is set up (stack, paca, etc)
*
+ * KVM:
+ * These interrupts do not elevate HV 0->1, so HV is not involved. PR KVM
+ * ensures that FSCR[SCV] is disabled whenever it has to force AIL off.
+ *
* Call convention:
*
* syscall register convention is in Documentation/powerpc/syscall64-abi.rst
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index be8577ac9397..d973ae7558e3 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -197,6 +197,34 @@ static void __init configure_exceptions(void)
/* Under a PAPR hypervisor, we need hypercalls */
if (firmware_has_feature(FW_FEATURE_SET_MODE)) {
+ /*
+ * - PR KVM does not support AIL mode interrupts in the host
+ * while a PR guest is running.
+ *
+ * - SCV system call interrupt vectors are only implemented for
+ * AIL mode interrupts.
+ *
+ * - On pseries, AIL mode can only be enabled and disabled
+ * system-wide so when a PR VM is created on a pseries host,
+ * all CPUs of the host are set to AIL=0 mode.
+ *
+ * - Therefore host CPUs must not execute scv while a PR VM
+ * exists.
+ *
+ * - SCV support can not be disabled dynamically because the
+ * feature is advertised to host userspace. Disabling the
+ * facility and emulating it would be possible but is not
+ * implemented.
+ *
+ * - So SCV support is blanket disabled if PR KVM could possibly
+ * run. That is, PR support compiled in, booting on pseries
+ * with hash MMU.
+ */
+ if (IS_ENABLED(CONFIG_KVM_BOOK3S_PR_POSSIBLE) && !radix_enabled()) {
+ init_task.thread.fscr &= ~FSCR_SCV;
+ cur_cpu_spec->cpu_user_features2 &= ~PPC_FEATURE2_SCV;
+ }
+
/* Enable AIL if possible */
if (!pseries_enable_reloc_on_exc()) {
init_task.thread.fscr &= ~FSCR_SCV;
diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
index 18e58085447c..ddd88179110a 100644
--- a/arch/powerpc/kvm/Kconfig
+++ b/arch/powerpc/kvm/Kconfig
@@ -112,12 +112,21 @@ config KVM_BOOK3S_64_PR
guest in user mode (problem state) and emulating all
privileged instructions and registers.
+ This is only available for hash MMU mode and only supports
+ guests that use hash MMU mode.
+
This is not as fast as using hypervisor mode, but works on
machines where hypervisor mode is not available or not usable,
and can emulate processors that are different from the host
processor, including emulating 32-bit processors on a 64-bit
host.
+ Selecting this option will cause the SCV facility to be
+ disabled when the kernel is booted on the pseries platform in
+ hash MMU mode (regardless of PR VMs running). When any PR VMs
+ are running, "AIL" mode is disabled which may slow interrupts
+ and system calls on the host.
+
config KVM_BOOK3S_HV_EXIT_TIMING
bool "Detailed timing for hypervisor real-mode code"
depends on KVM_BOOK3S_HV_POSSIBLE && DEBUG_FS
diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index 34a801c3604a..7bf9e6ca5c2d 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -137,12 +137,15 @@ static void kvmppc_core_vcpu_load_pr(struct kvm_vcpu *vcpu, int cpu)
svcpu->slb_max = to_book3s(vcpu)->slb_shadow_max;
svcpu->in_use = 0;
svcpu_put(svcpu);
-#endif
/* Disable AIL if supported */
- if (cpu_has_feature(CPU_FTR_HVMODE) &&
- cpu_has_feature(CPU_FTR_ARCH_207S))
- mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) & ~LPCR_AIL);
+ if (cpu_has_feature(CPU_FTR_HVMODE)) {
+ if (cpu_has_feature(CPU_FTR_ARCH_207S))
+ mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) & ~LPCR_AIL);
+ if (cpu_has_feature(CPU_FTR_ARCH_300) && (current->thread.fscr & FSCR_SCV))
+ mtspr(SPRN_FSCR, mfspr(SPRN_FSCR) & ~FSCR_SCV);
+ }
+#endif
vcpu->cpu = smp_processor_id();
#ifdef CONFIG_PPC_BOOK3S_32
@@ -165,6 +168,14 @@ static void kvmppc_core_vcpu_put_pr(struct kvm_vcpu *vcpu)
memcpy(to_book3s(vcpu)->slb_shadow, svcpu->slb, sizeof(svcpu->slb));
to_book3s(vcpu)->slb_shadow_max = svcpu->slb_max;
svcpu_put(svcpu);
+
+ /* Enable AIL if supported */
+ if (cpu_has_feature(CPU_FTR_HVMODE)) {
+ if (cpu_has_feature(CPU_FTR_ARCH_207S))
+ mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) | LPCR_AIL_3);
+ if (cpu_has_feature(CPU_FTR_ARCH_300) && (current->thread.fscr & FSCR_SCV))
+ mtspr(SPRN_FSCR, mfspr(SPRN_FSCR) | FSCR_SCV);
+ }
#endif
if (kvmppc_is_split_real(vcpu))
@@ -174,11 +185,6 @@ static void kvmppc_core_vcpu_put_pr(struct kvm_vcpu *vcpu)
kvmppc_giveup_fac(vcpu, FSCR_TAR_LG);
kvmppc_save_tm_pr(vcpu);
- /* Enable AIL if supported */
- if (cpu_has_feature(CPU_FTR_HVMODE) &&
- cpu_has_feature(CPU_FTR_ARCH_207S))
- mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) | LPCR_AIL_3);
-
vcpu->cpu = -1;
}
@@ -1037,6 +1043,8 @@ static int kvmppc_handle_fac(struct kvm_vcpu *vcpu, ulong fac)
void kvmppc_set_fscr(struct kvm_vcpu *vcpu, u64 fscr)
{
+ if (fscr & FSCR_SCV)
+ fscr &= ~FSCR_SCV; /* SCV must not be enabled */
if ((vcpu->arch.fscr & FSCR_TAR) && !(fscr & FSCR_TAR)) {
/* TAR got dropped, drop it in shadow too */
kvmppc_giveup_fac(vcpu, FSCR_TAR_LG);
--
2.23.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v3 2/3] KVM: PPC: Book3S PR: Disallow AIL != 0
2022-02-21 7:23 [PATCH v3 0/3] KVM: PPC: Book3S PR: Fixes for AIL and SCV Nicholas Piggin
2022-02-21 7:23 ` [PATCH v3 1/3] KVM: PPC: Book3S PR: Disable SCV when AIL could be disabled Nicholas Piggin
@ 2022-02-21 7:23 ` Nicholas Piggin
2022-02-21 7:23 ` [PATCH v3 3/3] KVM: PPC: Add KVM_CAP_PPC_AIL_MODE_3 Nicholas Piggin
2 siblings, 0 replies; 6+ messages in thread
From: Nicholas Piggin @ 2022-02-21 7:23 UTC (permalink / raw)
To: linuxppc-dev; +Cc: Nicholas Piggin, Fabiano Rosas
KVM PR does not implement address translation modes on interrupt, so it
must not allow H_SET_MODE to succeed. The behaviour change caused by
this mode is architected and not advisory (interrupts *must* behave
differently).
QEMU does not deal with differences in AIL support in the host. The
solution to that is a spapr capability and corresponding KVM CAP, but
this patch does not break things more than before (the host behaviour
already differs, this change just disallows some modes that are not
implemented properly).
By happy coincidence, this allows PR Linux guests that are using the SCV
facility to boot and run, because Linux disables the use of SCV if AIL
can not be set to 3. This does not fix the underlying problem of missing
SCV support (an OS could implement real-mode SCV vectors and try to
enable the facility). The true fix for that is for KVM PR to emulate scv
interrupts from the facility unavailable interrupt.
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
arch/powerpc/kvm/book3s_pr_papr.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/arch/powerpc/kvm/book3s_pr_papr.c b/arch/powerpc/kvm/book3s_pr_papr.c
index 1f10e7dfcdd0..dc4f51ac84bc 100644
--- a/arch/powerpc/kvm/book3s_pr_papr.c
+++ b/arch/powerpc/kvm/book3s_pr_papr.c
@@ -281,6 +281,22 @@ static int kvmppc_h_pr_logical_ci_store(struct kvm_vcpu *vcpu)
return EMULATE_DONE;
}
+static int kvmppc_h_pr_set_mode(struct kvm_vcpu *vcpu)
+{
+ unsigned long mflags = kvmppc_get_gpr(vcpu, 4);
+ unsigned long resource = kvmppc_get_gpr(vcpu, 5);
+
+ if (resource == H_SET_MODE_RESOURCE_ADDR_TRANS_MODE) {
+ /* KVM PR does not provide AIL!=0 to guests */
+ if (mflags == 0)
+ kvmppc_set_gpr(vcpu, 3, H_SUCCESS);
+ else
+ kvmppc_set_gpr(vcpu, 3, H_UNSUPPORTED_FLAG_START - 63);
+ return EMULATE_DONE;
+ }
+ return EMULATE_FAIL;
+}
+
#ifdef CONFIG_SPAPR_TCE_IOMMU
static int kvmppc_h_pr_put_tce(struct kvm_vcpu *vcpu)
{
@@ -384,6 +400,8 @@ int kvmppc_h_pr(struct kvm_vcpu *vcpu, unsigned long cmd)
return kvmppc_h_pr_logical_ci_load(vcpu);
case H_LOGICAL_CI_STORE:
return kvmppc_h_pr_logical_ci_store(vcpu);
+ case H_SET_MODE:
+ return kvmppc_h_pr_set_mode(vcpu);
case H_XIRR:
case H_CPPR:
case H_EOI:
@@ -421,6 +439,7 @@ int kvmppc_hcall_impl_pr(unsigned long cmd)
case H_CEDE:
case H_LOGICAL_CI_LOAD:
case H_LOGICAL_CI_STORE:
+ case H_SET_MODE:
#ifdef CONFIG_KVM_XICS
case H_XIRR:
case H_CPPR:
@@ -447,6 +466,7 @@ static unsigned int default_hcall_list[] = {
H_BULK_REMOVE,
H_PUT_TCE,
H_CEDE,
+ H_SET_MODE,
#ifdef CONFIG_KVM_XICS
H_XIRR,
H_CPPR,
--
2.23.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v3 3/3] KVM: PPC: Add KVM_CAP_PPC_AIL_MODE_3
2022-02-21 7:23 [PATCH v3 0/3] KVM: PPC: Book3S PR: Fixes for AIL and SCV Nicholas Piggin
2022-02-21 7:23 ` [PATCH v3 1/3] KVM: PPC: Book3S PR: Disable SCV when AIL could be disabled Nicholas Piggin
2022-02-21 7:23 ` [PATCH v3 2/3] KVM: PPC: Book3S PR: Disallow AIL != 0 Nicholas Piggin
@ 2022-02-21 7:23 ` Nicholas Piggin
2022-02-21 12:59 ` Fabiano Rosas
2022-02-22 3:34 ` Michael Ellerman
2 siblings, 2 replies; 6+ messages in thread
From: Nicholas Piggin @ 2022-02-21 7:23 UTC (permalink / raw)
To: linuxppc-dev; +Cc: Nicholas Piggin
Add KVM_CAP_PPC_AIL_MODE_3 to advertise the capability to set the AIL
resource mode to 3 with the H_SET_MODE hypercall. This capability
differs between processor types and KVM types (PR, HV, Nested HV), and
affects guest-visible behaviour.
QEMU will implement a cap-ail-mode-3 to control this behaviour[1], and
use the KVM CAP if available to determine KVM support[2].
[1] https://lists.nongnu.org/archive/html/qemu-ppc/2022-02/msg00437.html
[2] https://lists.nongnu.org/archive/html/qemu-ppc/2022-02/msg00439.html
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
Documentation/virt/kvm/api.rst | 14 ++++++++++++++
arch/powerpc/include/asm/setup.h | 2 ++
arch/powerpc/kvm/powerpc.c | 20 ++++++++++++++++++++
arch/powerpc/platforms/pseries/setup.c | 12 +++++++++++-
include/uapi/linux/kvm.h | 1 +
tools/include/uapi/linux/kvm.h | 1 +
6 files changed, 49 insertions(+), 1 deletion(-)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index bb8cfddbb22d..404056a9a35a 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6995,6 +6995,20 @@ indicated by the fd to the VM this is called on.
This is intended to support intra-host migration of VMs between userspace VMMs,
upgrading the VMM process without interrupting the guest.
+7.30 KVM_CAP_PPC_AIL_MODE_3
+-------------------------------
+
+:Capability: KVM_CAP_PPC_AIL_MODE_3
+:Architectures: ppc
+:Type: vm
+
+This capability indicates that the kernel supports the mode 3 setting for the
+"Address Translation Mode on Interrupt" aka "Alternate Interrupt Location"
+resource that is controlled with the H_SET_MODE hypercall.
+
+This capability allows a guest kernel to use a better-performance mode for
+handling interrupts and system calls.
+
8. Other capabilities.
======================
diff --git a/arch/powerpc/include/asm/setup.h b/arch/powerpc/include/asm/setup.h
index d0d3dd531c7f..a555fb77258a 100644
--- a/arch/powerpc/include/asm/setup.h
+++ b/arch/powerpc/include/asm/setup.h
@@ -28,11 +28,13 @@ void setup_panic(void);
#define ARCH_PANIC_TIMEOUT 180
#ifdef CONFIG_PPC_PSERIES
+extern bool pseries_reloc_on_exception(void);
extern bool pseries_enable_reloc_on_exc(void);
extern void pseries_disable_reloc_on_exc(void);
extern void pseries_big_endian_exceptions(void);
void __init pseries_little_endian_exceptions(void);
#else
+static inline bool pseries_reloc_on_exception(void) { return false; }
static inline bool pseries_enable_reloc_on_exc(void) { return false; }
static inline void pseries_disable_reloc_on_exc(void) {}
static inline void pseries_big_endian_exceptions(void) {}
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 2ad0ccd202d5..7dc101ea778c 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -678,6 +678,26 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
r = 1;
break;
#endif
+ case KVM_CAP_PPC_AIL_MODE_3:
+ /*
+ * KVM PR, POWER7, and some POWER9s don't support AIL=3 mode.
+ * The POWER9s can support it if the guest runs in hash mode,
+ * but QEMU doesn't necessarily query the capability in time.
+ */
+ if (hv_enabled) {
+ if (kvmhv_on_pseries()) {
+ if (pseries_reloc_on_exception())
+ r = 1;
+ } else if (cpu_has_feature(CPU_FTR_ARCH_207S) &&
+ !cpu_has_feature(CPU_FTR_P9_RADIX_PREFETCH_BUG)) {
+ r = 1;
+ } else {
+ r = 0;
+ }
+ } else {
+ r = 0;
+ }
+ break;
default:
r = 0;
break;
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 83a04d967a59..182525c2abd5 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -353,6 +353,13 @@ static void pseries_lpar_idle(void)
pseries_idle_epilog();
}
+static bool pseries_reloc_on_exception_enabled;
+
+bool pseries_reloc_on_exception(void)
+{
+ return pseries_reloc_on_exception_enabled;
+}
+
/*
* Enable relocation on during exceptions. This has partition wide scope and
* may take a while to complete, if it takes longer than one second we will
@@ -377,6 +384,7 @@ bool pseries_enable_reloc_on_exc(void)
" on exceptions: %ld\n", rc);
return false;
}
+ pseries_reloc_on_exception_enabled = true;
return true;
}
@@ -404,7 +412,9 @@ void pseries_disable_reloc_on_exc(void)
break;
mdelay(get_longbusy_msecs(rc));
}
- if (rc != H_SUCCESS)
+ if (rc == H_SUCCESS)
+ pseries_reloc_on_exception_enabled = false;
+ else
pr_warn("Warning: Failed to disable relocation on exceptions: %ld\n",
rc);
}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 9563d294f181..65f231d048a8 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1133,6 +1133,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM 206
#define KVM_CAP_VM_GPA_BITS 207
#define KVM_CAP_XSAVE2 208
+#define KVM_CAP_PPC_AIL_MODE_3 209
#ifdef KVM_CAP_IRQ_ROUTING
diff --git a/tools/include/uapi/linux/kvm.h b/tools/include/uapi/linux/kvm.h
index 9563d294f181..65f231d048a8 100644
--- a/tools/include/uapi/linux/kvm.h
+++ b/tools/include/uapi/linux/kvm.h
@@ -1133,6 +1133,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM 206
#define KVM_CAP_VM_GPA_BITS 207
#define KVM_CAP_XSAVE2 208
+#define KVM_CAP_PPC_AIL_MODE_3 209
#ifdef KVM_CAP_IRQ_ROUTING
--
2.23.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH v3 3/3] KVM: PPC: Add KVM_CAP_PPC_AIL_MODE_3
2022-02-21 7:23 ` [PATCH v3 3/3] KVM: PPC: Add KVM_CAP_PPC_AIL_MODE_3 Nicholas Piggin
@ 2022-02-21 12:59 ` Fabiano Rosas
2022-02-22 3:34 ` Michael Ellerman
1 sibling, 0 replies; 6+ messages in thread
From: Fabiano Rosas @ 2022-02-21 12:59 UTC (permalink / raw)
To: Nicholas Piggin, linuxppc-dev; +Cc: Nicholas Piggin
Nicholas Piggin <npiggin@gmail.com> writes:
> Add KVM_CAP_PPC_AIL_MODE_3 to advertise the capability to set the AIL
> resource mode to 3 with the H_SET_MODE hypercall. This capability
> differs between processor types and KVM types (PR, HV, Nested HV), and
> affects guest-visible behaviour.
>
> QEMU will implement a cap-ail-mode-3 to control this behaviour[1], and
> use the KVM CAP if available to determine KVM support[2].
>
> [1] https://lists.nongnu.org/archive/html/qemu-ppc/2022-02/msg00437.html
> [2] https://lists.nongnu.org/archive/html/qemu-ppc/2022-02/msg00439.html
>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
> ---
> Documentation/virt/kvm/api.rst | 14 ++++++++++++++
> arch/powerpc/include/asm/setup.h | 2 ++
> arch/powerpc/kvm/powerpc.c | 20 ++++++++++++++++++++
> arch/powerpc/platforms/pseries/setup.c | 12 +++++++++++-
> include/uapi/linux/kvm.h | 1 +
> tools/include/uapi/linux/kvm.h | 1 +
> 6 files changed, 49 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index bb8cfddbb22d..404056a9a35a 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -6995,6 +6995,20 @@ indicated by the fd to the VM this is called on.
> This is intended to support intra-host migration of VMs between userspace VMMs,
> upgrading the VMM process without interrupting the guest.
>
> +7.30 KVM_CAP_PPC_AIL_MODE_3
> +-------------------------------
> +
> +:Capability: KVM_CAP_PPC_AIL_MODE_3
> +:Architectures: ppc
> +:Type: vm
> +
> +This capability indicates that the kernel supports the mode 3 setting for the
> +"Address Translation Mode on Interrupt" aka "Alternate Interrupt Location"
> +resource that is controlled with the H_SET_MODE hypercall.
> +
> +This capability allows a guest kernel to use a better-performance mode for
> +handling interrupts and system calls.
> +
> 8. Other capabilities.
> ======================
>
> diff --git a/arch/powerpc/include/asm/setup.h b/arch/powerpc/include/asm/setup.h
> index d0d3dd531c7f..a555fb77258a 100644
> --- a/arch/powerpc/include/asm/setup.h
> +++ b/arch/powerpc/include/asm/setup.h
> @@ -28,11 +28,13 @@ void setup_panic(void);
> #define ARCH_PANIC_TIMEOUT 180
>
> #ifdef CONFIG_PPC_PSERIES
> +extern bool pseries_reloc_on_exception(void);
> extern bool pseries_enable_reloc_on_exc(void);
> extern void pseries_disable_reloc_on_exc(void);
> extern void pseries_big_endian_exceptions(void);
> void __init pseries_little_endian_exceptions(void);
> #else
> +static inline bool pseries_reloc_on_exception(void) { return false; }
> static inline bool pseries_enable_reloc_on_exc(void) { return false; }
> static inline void pseries_disable_reloc_on_exc(void) {}
> static inline void pseries_big_endian_exceptions(void) {}
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 2ad0ccd202d5..7dc101ea778c 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -678,6 +678,26 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> r = 1;
> break;
> #endif
> + case KVM_CAP_PPC_AIL_MODE_3:
> + /*
> + * KVM PR, POWER7, and some POWER9s don't support AIL=3 mode.
> + * The POWER9s can support it if the guest runs in hash mode,
> + * but QEMU doesn't necessarily query the capability in time.
> + */
> + if (hv_enabled) {
> + if (kvmhv_on_pseries()) {
> + if (pseries_reloc_on_exception())
> + r = 1;
> + } else if (cpu_has_feature(CPU_FTR_ARCH_207S) &&
> + !cpu_has_feature(CPU_FTR_P9_RADIX_PREFETCH_BUG)) {
> + r = 1;
> + } else {
> + r = 0;
> + }
> + } else {
> + r = 0;
> + }
> + break;
> default:
> r = 0;
> break;
> diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
> index 83a04d967a59..182525c2abd5 100644
> --- a/arch/powerpc/platforms/pseries/setup.c
> +++ b/arch/powerpc/platforms/pseries/setup.c
> @@ -353,6 +353,13 @@ static void pseries_lpar_idle(void)
> pseries_idle_epilog();
> }
>
> +static bool pseries_reloc_on_exception_enabled;
> +
> +bool pseries_reloc_on_exception(void)
> +{
> + return pseries_reloc_on_exception_enabled;
> +}
> +
> /*
> * Enable relocation on during exceptions. This has partition wide scope and
> * may take a while to complete, if it takes longer than one second we will
> @@ -377,6 +384,7 @@ bool pseries_enable_reloc_on_exc(void)
> " on exceptions: %ld\n", rc);
> return false;
> }
> + pseries_reloc_on_exception_enabled = true;
> return true;
> }
>
> @@ -404,7 +412,9 @@ void pseries_disable_reloc_on_exc(void)
> break;
> mdelay(get_longbusy_msecs(rc));
> }
> - if (rc != H_SUCCESS)
> + if (rc == H_SUCCESS)
> + pseries_reloc_on_exception_enabled = false;
> + else
> pr_warn("Warning: Failed to disable relocation on exceptions: %ld\n",
> rc);
> }
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 9563d294f181..65f231d048a8 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1133,6 +1133,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM 206
> #define KVM_CAP_VM_GPA_BITS 207
> #define KVM_CAP_XSAVE2 208
> +#define KVM_CAP_PPC_AIL_MODE_3 209
>
> #ifdef KVM_CAP_IRQ_ROUTING
>
> diff --git a/tools/include/uapi/linux/kvm.h b/tools/include/uapi/linux/kvm.h
> index 9563d294f181..65f231d048a8 100644
> --- a/tools/include/uapi/linux/kvm.h
> +++ b/tools/include/uapi/linux/kvm.h
> @@ -1133,6 +1133,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM 206
> #define KVM_CAP_VM_GPA_BITS 207
> #define KVM_CAP_XSAVE2 208
> +#define KVM_CAP_PPC_AIL_MODE_3 209
>
> #ifdef KVM_CAP_IRQ_ROUTING
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH v3 3/3] KVM: PPC: Add KVM_CAP_PPC_AIL_MODE_3
2022-02-21 7:23 ` [PATCH v3 3/3] KVM: PPC: Add KVM_CAP_PPC_AIL_MODE_3 Nicholas Piggin
2022-02-21 12:59 ` Fabiano Rosas
@ 2022-02-22 3:34 ` Michael Ellerman
1 sibling, 0 replies; 6+ messages in thread
From: Michael Ellerman @ 2022-02-22 3:34 UTC (permalink / raw)
To: Nicholas Piggin, linuxppc-dev; +Cc: Nicholas Piggin
Nicholas Piggin <npiggin@gmail.com> writes:
> Add KVM_CAP_PPC_AIL_MODE_3 to advertise the capability to set the AIL
> resource mode to 3 with the H_SET_MODE hypercall. This capability
> differs between processor types and KVM types (PR, HV, Nested HV), and
> affects guest-visible behaviour.
>
> QEMU will implement a cap-ail-mode-3 to control this behaviour[1], and
> use the KVM CAP if available to determine KVM support[2].
>
> [1] https://lists.nongnu.org/archive/html/qemu-ppc/2022-02/msg00437.html
> [2] https://lists.nongnu.org/archive/html/qemu-ppc/2022-02/msg00439.html
>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
> Documentation/virt/kvm/api.rst | 14 ++++++++++++++
> arch/powerpc/include/asm/setup.h | 2 ++
> arch/powerpc/kvm/powerpc.c | 20 ++++++++++++++++++++
> arch/powerpc/platforms/pseries/setup.c | 12 +++++++++++-
> include/uapi/linux/kvm.h | 1 +
> tools/include/uapi/linux/kvm.h | 1 +
> 6 files changed, 49 insertions(+), 1 deletion(-)
This one especially, but may as well be the whole series, needs to be
Cc'ed to kvm@vger.kernel.org, so that the generic KVM folks are aware of
it.
Can you do a resend Cc'ing them please.
cheers
^ permalink raw reply [flat|nested] 6+ messages in thread