* [PATCH] perf/x86/kvm: Fix Broadwell Xeon stepping in isolation_ucodes[]
@ 2021-04-22 0:18 Jim Mattson
2021-04-22 2:05 ` Andi Kleen
2021-04-23 6:53 ` [tip: perf/urgent] " tip-bot2 for Jim Mattson
0 siblings, 2 replies; 3+ messages in thread
From: Jim Mattson @ 2021-04-22 0:18 UTC (permalink / raw)
To: Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Mark Rutland, Alexander Shishkin, Jiri Olsa, Namhyung Kim,
Thomas Gleixner, Borislav Petkov, x86, H. Peter Anvin, Kan Liang,
Andi Kleen, linux-kernel, kvm-list
Cc: Jim Mattson, Peter Shier
The only stepping of Broadwell Xeon parts is stepping 1. Fix the
relevant isolation_ucodes[] entry, which previously enumerated
stepping 2.
Although the original commit was characterized as an optimization, it
is also a workaround for a correctness issue.
If a PMI arrives between kvm's call to perf_guest_get_msrs() and the
subsequent VM-entry, a stale value for the IA32_PEBS_ENABLE MSR may be
restored at the next VM-exit. This is because, unbeknownst to kvm, PMI
throttling may clear bits in the IA32_PEBS_ENABLE MSR. CPUs with "PEBS
isolation" don't suffer from this issue, because perf_guest_get_msrs()
doesn't report the IA32_PEBS_ENABLE value.
Fixes: 9b545c04abd4f ("perf/x86/kvm: Avoid unnecessary work in guest filtering")
Cc: Andi Kleen <ak@linux.intel.com>
Reported-by: Peter Shier <pshier@google.com>
Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
---
arch/x86/events/intel/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 37ce38403cb8..c57ec8e27907 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -4516,7 +4516,7 @@ static const struct x86_cpu_desc isolation_ucodes[] = {
INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_D, 3, 0x07000009),
INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_D, 4, 0x0f000009),
INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_D, 5, 0x0e000002),
- INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_X, 2, 0x0b000014),
+ INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_X, 1, 0x0b000014),
INTEL_CPU_DESC(INTEL_FAM6_SKYLAKE_X, 3, 0x00000021),
INTEL_CPU_DESC(INTEL_FAM6_SKYLAKE_X, 4, 0x00000000),
INTEL_CPU_DESC(INTEL_FAM6_SKYLAKE_X, 5, 0x00000000),
--
2.31.1.368.gbe11c130af-goog
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] perf/x86/kvm: Fix Broadwell Xeon stepping in isolation_ucodes[]
2021-04-22 0:18 [PATCH] perf/x86/kvm: Fix Broadwell Xeon stepping in isolation_ucodes[] Jim Mattson
@ 2021-04-22 2:05 ` Andi Kleen
2021-04-23 6:53 ` [tip: perf/urgent] " tip-bot2 for Jim Mattson
1 sibling, 0 replies; 3+ messages in thread
From: Andi Kleen @ 2021-04-22 2:05 UTC (permalink / raw)
To: Jim Mattson
Cc: Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Mark Rutland, Alexander Shishkin, Jiri Olsa, Namhyung Kim,
Thomas Gleixner, Borislav Petkov, x86, H. Peter Anvin, Kan Liang,
linux-kernel, kvm-list, Peter Shier
On Wed, Apr 21, 2021 at 05:18:34PM -0700, Jim Mattson wrote:
> The only stepping of Broadwell Xeon parts is stepping 1. Fix the
> relevant isolation_ucodes[] entry, which previously enumerated
> stepping 2.
>
> Although the original commit was characterized as an optimization, it
> is also a workaround for a correctness issue.
>
> If a PMI arrives between kvm's call to perf_guest_get_msrs() and the
> subsequent VM-entry, a stale value for the IA32_PEBS_ENABLE MSR may be
> restored at the next VM-exit. This is because, unbeknownst to kvm, PMI
> throttling may clear bits in the IA32_PEBS_ENABLE MSR. CPUs with "PEBS
> isolation" don't suffer from this issue, because perf_guest_get_msrs()
> doesn't report the IA32_PEBS_ENABLE value.
Acked-by: Andi Kleen <ak@linux.intel.com>
-Andi
^ permalink raw reply [flat|nested] 3+ messages in thread
* [tip: perf/urgent] perf/x86/kvm: Fix Broadwell Xeon stepping in isolation_ucodes[]
2021-04-22 0:18 [PATCH] perf/x86/kvm: Fix Broadwell Xeon stepping in isolation_ucodes[] Jim Mattson
2021-04-22 2:05 ` Andi Kleen
@ 2021-04-23 6:53 ` tip-bot2 for Jim Mattson
1 sibling, 0 replies; 3+ messages in thread
From: tip-bot2 for Jim Mattson @ 2021-04-23 6:53 UTC (permalink / raw)
To: linux-tip-commits
Cc: Jim Mattson, Peter Zijlstra (Intel),
Peter Shier, Andi Kleen, x86, linux-kernel
The following commit has been merged into the perf/urgent branch of tip:
Commit-ID: 4b2f1e59229b9da319d358828cdfa4ddbc140769
Gitweb: https://git.kernel.org/tip/4b2f1e59229b9da319d358828cdfa4ddbc140769
Author: Jim Mattson <jmattson@google.com>
AuthorDate: Wed, 21 Apr 2021 17:18:34 -07:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Thu, 22 Apr 2021 14:36:01 +02:00
perf/x86/kvm: Fix Broadwell Xeon stepping in isolation_ucodes[]
The only stepping of Broadwell Xeon parts is stepping 1. Fix the
relevant isolation_ucodes[] entry, which previously enumerated
stepping 2.
Although the original commit was characterized as an optimization, it
is also a workaround for a correctness issue.
If a PMI arrives between kvm's call to perf_guest_get_msrs() and the
subsequent VM-entry, a stale value for the IA32_PEBS_ENABLE MSR may be
restored at the next VM-exit. This is because, unbeknownst to kvm, PMI
throttling may clear bits in the IA32_PEBS_ENABLE MSR. CPUs with "PEBS
isolation" don't suffer from this issue, because perf_guest_get_msrs()
doesn't report the IA32_PEBS_ENABLE value.
Fixes: 9b545c04abd4f ("perf/x86/kvm: Avoid unnecessary work in guest filtering")
Signed-off-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Peter Shier <pshier@google.com>
Acked-by: Andi Kleen <ak@linux.intel.com>
Link: https://lkml.kernel.org/r/20210422001834.1748319-1-jmattson@google.com
---
arch/x86/events/intel/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 37ce384..c57ec8e 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -4516,7 +4516,7 @@ static const struct x86_cpu_desc isolation_ucodes[] = {
INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_D, 3, 0x07000009),
INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_D, 4, 0x0f000009),
INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_D, 5, 0x0e000002),
- INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_X, 2, 0x0b000014),
+ INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_X, 1, 0x0b000014),
INTEL_CPU_DESC(INTEL_FAM6_SKYLAKE_X, 3, 0x00000021),
INTEL_CPU_DESC(INTEL_FAM6_SKYLAKE_X, 4, 0x00000000),
INTEL_CPU_DESC(INTEL_FAM6_SKYLAKE_X, 5, 0x00000000),
^ permalink raw reply related [flat|nested] 3+ messages in thread
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2021-04-22 0:18 [PATCH] perf/x86/kvm: Fix Broadwell Xeon stepping in isolation_ucodes[] Jim Mattson
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2021-04-23 6:53 ` [tip: perf/urgent] " tip-bot2 for Jim Mattson
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