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authorLadi Prosek <lprosek@redhat.com>2017-07-26 14:32:59 +0300
committerPaolo Bonzini <pbonzini@redhat.com>2017-08-07 16:26:06 +0300
commit72c139bacfa386145d7bbb68c47c8824716153b6 (patch)
tree2661bf0f4153e7e302c78f1a849049db1b15a6e5 /arch/x86/kvm/lapic.h
parentaae4e7a8bc44722fe70d58920a36916b1043195e (diff)
downloadlinux-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/lapic.h')
-rw-r--r--arch/x86/kvm/lapic.h3
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 */