Setting the TSC deadline MSR that are initiated by the host (using ioctl's) may
cause superfluous interrupt. This occurs in the following case:
1. A TSC deadline timer interrupt is pending.
2. TSC deadline was still not cleared (which happens during vcpu_run).
3. Userspace uses KVM_GET_MSRS/KVM_SET_MSRS to load the same deadline msr.
To solve this situation, ignore host initiated TSC deadline writes that do not
change the deadline value.
Signed-off-by: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/lapic.c | 7 ++++++-
arch/x86/kvm/lapic.h | 3 ++-
arch/x86/kvm/x86.c | 2 +-
3 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index b8345dd..0bcf2e1 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1346,14 +1346,19 @@ u64 kvm_get_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu)
return apic->lapic_timer.tscdeadline;
}
-void kvm_set_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu, u64 data)
+void kvm_set_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu,
+ struct msr_data *msr_info)
{
struct kvm_lapic *apic = vcpu->arch.apic;
+ u64 data = msr_info->data;
if (!kvm_vcpu_has_lapic(vcpu) || apic_lvtt_oneshot(apic) ||
apic_lvtt_period(apic))
return;
+ if (msr_info->host_initiated && apic->lapic_timer.tscdeadline == data)
+ return;
+
hrtimer_cancel(&apic->lapic_timer.timer);
/* Inject here so clearing tscdeadline won't override new value */
if (apic_has_pending_timer(vcpu))
diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
index 6a11845..5bfa3db 100644
--- a/arch/x86/kvm/lapic.h
+++ b/arch/x86/kvm/lapic.h
@@ -71,7 +71,8 @@ void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu,
int kvm_lapic_find_highest_irr(struct kvm_vcpu *vcpu);
u64 kvm_get_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu);
-void kvm_set_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu, u64 data);
+void kvm_set_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu,
+ struct msr_data *msr_info);
void kvm_apic_write_nodecode(struct kvm_vcpu *vcpu, u32 offset);
void kvm_apic_set_eoi_accelerated(struct kvm_vcpu *vcpu, int vector);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e903167..8c2745c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2093,7 +2093,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
case APIC_BASE_MSR ... APIC_BASE_MSR + 0x3ff:
return kvm_x2apic_msr_write(vcpu, msr, data);
case MSR_IA32_TSCDEADLINE:
- kvm_set_lapic_tscdeadline_msr(vcpu, data);
+ kvm_set_lapic_tscdeadline_msr(vcpu, msr_info);
break;
case MSR_IA32_TSC_ADJUST:
if (guest_cpuid_has_tsc_adjust(vcpu)) {
--
1.9.1
--
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