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Date: Tue, 3 May 2022 14:01:18 +0200 From: Paolo Bonzini <pbonzini@...hat.com> To: Jim Mattson <jmattson@...gle.com>, Sandipan Das <sandipan.das@....com> Cc: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org, x86@...nel.org, peterz@...radead.org, bp@...en8.de, dave.hansen@...ux.intel.com, acme@...nel.org, mark.rutland@....com, alexander.shishkin@...ux.intel.com, namhyung@...nel.org, jolsa@...nel.org, tglx@...utronix.de, mingo@...hat.com, like.xu.linux@...il.com, eranian@...gle.com, puwen@...on.cn, ananth.narayan@....com, ravi.bangoria@....com, santosh.shukla@....com Subject: Re: [PATCH v4 7/7] kvm: x86/cpuid: Fix CPUID leaf 0xA On 5/3/22 01:50, Jim Mattson wrote: > On Wed, Apr 27, 2022 at 4:34 AM Sandipan Das <sandipan.das@....com> wrote: >> >> On some x86 processors, CPUID leaf 0xA provides information >> on Architectural Performance Monitoring features. It >> advertises a PMU version which Qemu uses to determine the >> availability of additional MSRs to manage the PMCs. >> >> Upon receiving a KVM_GET_SUPPORTED_CPUID ioctl request for >> the same, the kernel constructs return values based on the >> x86_pmu_capability irrespective of the vendor. >> >> This leaf and the additional MSRs are not supported on AMD >> and Hygon processors. If AMD PerfMonV2 is detected, the PMU >> version is set to 2 and guest startup breaks because of an >> attempt to access a non-existent MSR. Return zeros to avoid >> this. >> >> Fixes: a6c06ed1a60a ("KVM: Expose the architectural performance monitoring CPUID leaf") >> Reported-by: Vasant Hegde <vasant.hegde@....com> >> Signed-off-by: Sandipan Das <sandipan.das@....com> >> --- >> arch/x86/kvm/cpuid.c | 5 +++++ >> 1 file changed, 5 insertions(+) >> >> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c >> index 4b62d80bb22f..e66ebb747084 100644 >> --- a/arch/x86/kvm/cpuid.c >> +++ b/arch/x86/kvm/cpuid.c >> @@ -872,6 +872,11 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) >> union cpuid10_eax eax; >> union cpuid10_edx edx; >> >> + if (!static_cpu_has(X86_FEATURE_ARCH_PERFMON)) { > > Should this be checking kvm_cpu_cap_has(X86_FEATURE_ARCH_PERFMON) instead? Yes, it should. I have queued this patch for 5.18. Paolo
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