This is a note to let you know that I've just added the patch titled perf/x86/kvm: Fix Broadwell Xeon stepping in isolation_ucodes[] to the 5.11-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: perf-x86-kvm-fix-broadwell-xeon-stepping-in-isolatio.patch and it can be found in the queue-5.11 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 320b04a3d7292be2fbfe9865089c9a84261bee92 Author: Jim Mattson <jmattson@xxxxxxxxxx> Date: Wed Apr 21 17:18:34 2021 -0700 perf/x86/kvm: Fix Broadwell Xeon stepping in isolation_ucodes[] [ Upstream commit 4b2f1e59229b9da319d358828cdfa4ddbc140769 ] 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@xxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Peter Shier <pshier@xxxxxxxxxx> Acked-by: Andi Kleen <ak@xxxxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20210422001834.1748319-1-jmattson@xxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c index bfd42e0853ed..6c88f245b33a 100644 --- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -4400,7 +4400,7 @@ 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),