Re: [PATCH] KVM: VMX: Always treat MSR_IA32_PERF_CAPABILITIES as a valid PMU MSR

[Xu, Like]

On 2020/6/4 4:33, Sean Christopherson wrote:
Unconditionally return true when querying the validity of
MSR_IA32_PERF_CAPABILITIES so as to defer the validity check to
intel_pmu_{get,set}_msr(), which can properly give the MSR a pass when
the access is initiated from host userspace.
Regardless of  the MSR is emulated or not, is it a really good assumption that
the guest cpuids are not properly ready when we do initialization from host 
userspace
?
The MSR is emulated so
there is no underlying hardware dependency to worry about.
Fixes: 27461da31089a ("KVM: x86/pmu: Support full width counting")
Cc: Like Xu <like...@linux.intel.com>
Signed-off-by: Sean Christopherson <sean.j.christopher...@intel.com>
---

KVM selftests are completely hosed for me, everything fails on KVM_GET_MSRS.
At least I tried "make --silent -C tools/testing/selftests/kvm run_tests"
and how do I reproduce the "everything fails" for this issue ?

Thanks,
Like Xu

  arch/x86/kvm/vmx/pmu_intel.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index d33d890b605f..bdcce65c7a1d 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -181,7 +181,7 @@ static bool intel_is_valid_msr(struct kvm_vcpu *vcpu, u32 
msr)
                ret = pmu->version > 1;
                break;
        case MSR_IA32_PERF_CAPABILITIES:
-               ret = guest_cpuid_has(vcpu, X86_FEATURE_PDCM);
+               ret = 1;
                break;
        default:
                ret = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0) ||