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SubjectRe: [PATCH v4 7/7] kvm: x86/cpuid: Fix CPUID leaf 0xA
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On 5/3/22 01:50, Jim Mattson wrote:
> On Wed, Apr 27, 2022 at 4:34 AM Sandipan Das <sandipan.das@amd.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@amd.com>
>> Signed-off-by: Sandipan Das <sandipan.das@amd.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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