Messages in this thread | | | Date | Tue, 26 Apr 2022 14:10:43 +0530 | Subject | Re: [PATCH v2 7/7] kvm: x86/cpuid: Fix CPUID leaf 0xA | From | Sandipan Das <> |
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Hi Peter,
On 4/26/2022 1:45 PM, Peter Zijlstra wrote: > On Thu, Apr 21, 2022 at 11:16:59AM +0530, 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 >> 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 4b62d80bb22f..6bd65cad75ef 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 (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) { > > This is the obligatory question about HYGON; should they be included > here? > > x86 is getting a number of me-too patches from both sides, where > behaviour has diverged for no raisin and then needs to be fixed up > again. >
From what I understand, Hygon processors also do not support this leaf. Copying Pu Wen for confirmation.
- Sandipan
>> + entry->eax = entry->ebx = entry->ecx = entry->edx = 0; >> + break; >> + } >> + >> perf_get_x86_pmu_capability(&cap); >> >> /* >> -- >> 2.32.0 >>
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