From: Ladi Prosek <lprosek@redhat.com>
Date: Wed, 26 Jul 2017 13:32:59 +0200
Subject: KVM: hyperv: support HV_X64_MSR_TSC_FREQUENCY and
HV_X64_MSR_APIC_FREQUENCY
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Patch-mainline: v4.14-rc1
Git-commit: 72c139bacfa386145d7bbb68c47c8824716153b6
References: bsc#1077761
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>
Acked-by: Alexander Graf <agraf@suse.de>
---
arch/x86/kvm/hyperv.c | 6 ++++++
arch/x86/kvm/lapic.c | 2 --
arch/x86/kvm/lapic.h | 3 +++
arch/x86/kvm/x86.c | 1 +
4 files changed, 10 insertions(+), 2 deletions(-)
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1160,6 +1160,12 @@
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;
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -54,8 +54,6 @@
#define PRIu64 "u"
#define PRIo64 "o"
-#define APIC_BUS_CYCLE_NS 1
-
/* #define apic_debug(fmt,arg...) printk(KERN_WARNING fmt,##arg) */
#define apic_debug(fmt, arg...)
--- 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 */
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -994,6 +994,7 @@
MSR_KVM_SYSTEM_TIME_NEW, MSR_KVM_WALL_CLOCK_NEW,
HV_X64_MSR_GUEST_OS_ID, HV_X64_MSR_HYPERCALL,
HV_X64_MSR_TIME_REF_COUNT, HV_X64_MSR_REFERENCE_TSC,
+ HV_X64_MSR_TSC_FREQUENCY, HV_X64_MSR_APIC_FREQUENCY,
HV_X64_MSR_CRASH_P0, HV_X64_MSR_CRASH_P1, HV_X64_MSR_CRASH_P2,
HV_X64_MSR_CRASH_P3, HV_X64_MSR_CRASH_P4, HV_X64_MSR_CRASH_CTL,
HV_X64_MSR_RESET,