Messages in this thread | | | Date | Thu, 17 Mar 2022 13:07:47 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 7/7] kvm: x86/cpuid: Fix Architectural Performance Monitoring support |
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On Thu, Mar 17, 2022 at 11:58:36AM +0530, Sandipan Das wrote: > CPUID 0xA provides information on Architectural Performance > Monitoring features on some x86 processors. 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 CPUID function and additional MSRs are not supported on > AMD processors. If 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 b8f8d268d058..1d9ca5726167 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -865,6 +865,11 @@ 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) { > + entry->eax = entry->ebx = entry->ecx = entry->edx = 0; > + break; > + } > +
Because actually implementing perfmon-v2 would've been too convenient, right? IIRC you're very close to actually supporing perfmon-v2 capability wise here.
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