I missed this patch last week, sorry. 2017-07-17 15:28+0200, Ladi Prosek: > It has been experimentally confirmed that supporting these two MSRs is one > of the necessary conditions for nested Hyper-V to use the TSC page. Modern > Windows guests are noticeably slower when they fall back to reading > timestamps from the HV_X64_MSR_TIME_REF_COUNT MSR instead of using the TSC > page. > > The newly supported MSRs are advertised with the AccessFrequencyRegs > partition privilege flag and CPUID.40000003H:EDX[8] "Support for > determining timer frequencies is available" (both outside of the scope of > this KVM patch). Do Windows ignore the AccessFrequencyMsrs (CPUID.40000003H:EAX[11]) bit? > Hypervisor Top Level Functional Specification version 5.0b does not > explicitly mark these MSRs as partition wide. This is, however, implied by > the way Windows uses them (one read on Hyper-V startup regardless of the > number of VCPUs) as well as our implementation. > > Signed-off-by: Ladi Prosek <lprosek@xxxxxxxxxx> > --- > diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c > @@ -1065,6 +1067,12 @@ static int kvm_hv_get_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata) > case HV_X64_MSR_REFERENCE_TSC: > data = hv->hv_tsc_page; > break; > + case HV_X64_MSR_TSC_FREQUENCY: > + data = (u64)tsc_khz * 1000; > + break; This should be based on vcpu->arch.virtual_tsc_khz, because KVM can use guest TSC scaling, thanks. > + case HV_X64_MSR_APIC_FREQUENCY: > + data = APIC_BUS_FREQUENCY; > + break; > case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4: > return kvm_hv_msr_get_crash_data(vcpu, > msr - HV_X64_MSR_CRASH_P0,
