2017-07-26 13:32+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). > Signed-off-by: Ladi Prosek <lprosek@xxxxxxxxxx> > --- > > v1->v2: > * HV_X64_MSR_TSC_FREQUENCY now based on vcpu->arch.virtual_tsc_khz (Radim) > * Removed both MSRs from the partition-wide list as the implementation is > no longer vcpu agnostic I like that we don't have to add a capability to expose this feature to the userspace, Reviewed-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
