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SubjectRe: [PATCH v3 7/7] kvm: x86/cpuid: Fix CPUID leaf 0xA
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On 26/4/2022 9:05 pm, Sandipan Das 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

So, why not:

if (!static_cpu_has(X86_FEATURE_ARCH_PERFMON))
break;
?

> 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 | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 4b62d80bb22f..d27d6a8f601a 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -872,6 +872,12 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
> union cpuid10_eax eax;
> union cpuid10_edx edx;
>
> + if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
> + boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
> + entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
> + break;
> + }
> +
> perf_get_x86_pmu_capability(&cap);
>
> /*

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