diff options
| author | Ladi Prosek <lprosek@redhat.com> | 2017-07-26 13:32:59 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2017-08-07 15:26:06 +0200 |
| commit | 72c139bacfa386145d7bbb68c47c8824716153b6 (patch) | |
| tree | 2661bf0f4153e7e302c78f1a849049db1b15a6e5 /arch/x86/kvm/lapic.h | |
| parent | aae4e7a8bc44722fe70d58920a36916b1043195e (diff) | |
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/lapic.h')
| -rw-r--r-- | arch/x86/kvm/lapic.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h index 29caa2c3dff9..215721e1426a 100644 --- a/arch/x86/kvm/lapic.h +++ b/arch/x86/kvm/lapic.h @@ -12,6 +12,9 @@ #define KVM_APIC_SHORT_MASK 0xc0000 #define KVM_APIC_DEST_MASK 0x800 +#define APIC_BUS_CYCLE_NS 1 +#define APIC_BUS_FREQUENCY (1000000000ULL / APIC_BUS_CYCLE_NS) + struct kvm_timer { struct hrtimer timer; s64 period; /* unit: ns */ |