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| author | Ladi Prosek <lprosek@redhat.com> | 2017-07-26 14:32:59 +0300 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2017-08-07 16:26:06 +0300 |
| commit | 72c139bacfa386145d7bbb68c47c8824716153b6 (patch) | |
| tree | 2661bf0f4153e7e302c78f1a849049db1b15a6e5 /arch/x86/kvm/hyperv.c | |
| parent | aae4e7a8bc44722fe70d58920a36916b1043195e (diff) | |
| download | linux-72c139bacfa386145d7bbb68c47c8824716153b6.tar.xz | |
KVM: hyperv: support HV_X64_MSR_TSC_FREQUENCY and HV_X64_MSR_APIC_FREQUENCY
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).
Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Ladi Prosek <lprosek@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/hyperv.c')
| -rw-r--r-- | arch/x86/kvm/hyperv.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index 337b6d2730fa..bf9992300efa 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -1160,6 +1160,12 @@ static int kvm_hv_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata) return stimer_get_count(vcpu_to_stimer(vcpu, timer_index), pdata); } + case HV_X64_MSR_TSC_FREQUENCY: + data = (u64)vcpu->arch.virtual_tsc_khz * 1000; + break; + case HV_X64_MSR_APIC_FREQUENCY: + data = APIC_BUS_FREQUENCY; + break; default: vcpu_unimpl(vcpu, "Hyper-V unhandled rdmsr: 0x%x\n", msr); return 1; |