[lvc-project] [PATCH 5.10 2/3] KVM: LAPIC: Write 0 to TMICT should also cancel vmx-preemption timer

[Roman Demidov]

From: Wanpeng Li <wanpengli at tencent.com>

commit e898da784aed0ea65f7672d941c01dc9b79e6299 upstream.

According to the SDM 10.5.4.1:

  A write of 0 to the initial-count register effectively stops the local
  APIC timer, in both one-shot and periodic mode.

However, the lapic timer oneshot/periodic mode which is emulated by vmx-preemption
timer doesn't stop by writing 0 to TMICT since vmx->hv_deadline_tsc is still
programmed and the guest will receive the spurious timer interrupt later. This
patch fixes it by also cancelling the vmx-preemption timer when writing 0 to
the initial-count register.

Reviewed-by: Sean Christopherson <seanjc at google.com>
Signed-off-by: Wanpeng Li <wanpengli at tencent.com>
Message-Id: <1623050385-100988-1-git-send-email-wanpengli at tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
Stable-dep-of: 54b3439c8e70 ("KVM: LAPIC: Also cancel preemption timer during SET_LAPIC")
Signed-off-by: Roman Demidov <roman.demidov.nn at gmail.com>
---
 arch/x86/kvm/lapic.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 8f41a5ecea22..c17628c30c8c 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1491,6 +1491,15 @@ static void limit_periodic_timer_frequency(struct kvm_lapic *apic)
 
 static void cancel_hv_timer(struct kvm_lapic *apic);
 
+static void cancel_apic_timer(struct kvm_lapic *apic)
+{
+	hrtimer_cancel(&apic->lapic_timer.timer);
+	preempt_disable();
+	if (apic->lapic_timer.hv_timer_in_use)
+		cancel_hv_timer(apic);
+	preempt_enable();
+}
+
 static void apic_update_lvtt(struct kvm_lapic *apic)
 {
 	u32 timer_mode = kvm_lapic_get_reg(apic, APIC_LVTT) &
@@ -1499,11 +1508,7 @@ static void apic_update_lvtt(struct kvm_lapic *apic)
 	if (apic->lapic_timer.timer_mode != timer_mode) {
 		if (apic_lvtt_tscdeadline(apic) != (timer_mode ==
 				APIC_LVT_TIMER_TSCDEADLINE)) {
-			hrtimer_cancel(&apic->lapic_timer.timer);
-			preempt_disable();
-			if (apic->lapic_timer.hv_timer_in_use)
-				cancel_hv_timer(apic);
-			preempt_enable();
+			cancel_apic_timer(apic);
 			kvm_lapic_set_reg(apic, APIC_TMICT, 0);
 			apic->lapic_timer.period = 0;
 			apic->lapic_timer.tscdeadline = 0;
@@ -2099,7 +2104,7 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
 		if (apic_lvtt_tscdeadline(apic))
 			break;
 
-		hrtimer_cancel(&apic->lapic_timer.timer);
+		cancel_apic_timer(apic);
 		kvm_lapic_set_reg(apic, APIC_TMICT, val);
 		start_apic_timer(apic);
 		break;
-- 
2.53.0