From 72c139bacfa386145d7bbb68c47c8824716153b6 Mon Sep 17 00:00:00 2001 From: Ladi Prosek Date: Wed, 26 Jul 2017 13:32:59 +0200 Subject: KVM: hyperv: support HV_X64_MSR_TSC_FREQUENCY and HV_X64_MSR_APIC_FREQUENCY MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Ladi Prosek Signed-off-by: Paolo Bonzini --- arch/x86/kvm/hyperv.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'arch/x86/kvm/hyperv.c') 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; -- cgit v1.2.3