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Subject[PATCH] KVM: LAPIC: Accurately guarantee busy wait for timer to expire when using hv_timer
Date
From: Wanpeng Li <wanpengli@tencent.com>

Commit ee66e453db13d (KVM: lapic: Busy wait for timer to expire when
using hv_timer) tries to set ktime->expired_tscdeadline by checking
ktime->hv_timer_in_use since lapic timer oneshot/periodic modes which
are emulated by vmx preemption timer also get advanced, they leverage
the same vmx preemption timer logic with tsc-deadline mode. However,
ktime->hv_timer_in_use is cleared before apic_timer_expired() handling,
let's delay this clearing in preemption-disabled region.

Fixes: ee66e453db13d (KVM: lapic: Busy wait for timer to expire when using hv_timer)
Cc: Sean Christopherson <seanjc@google.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
arch/x86/kvm/lapic.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 152591f..c0ebef5 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1913,8 +1913,8 @@ void kvm_lapic_expired_hv_timer(struct kvm_vcpu *vcpu)
if (!apic->lapic_timer.hv_timer_in_use)
goto out;
WARN_ON(rcuwait_active(&vcpu->wait));
- cancel_hv_timer(apic);
apic_timer_expired(apic, false);
+ cancel_hv_timer(apic);

if (apic_lvtt_period(apic) && apic->lapic_timer.period) {
advance_periodic_target_expiration(apic);
--
2.7.4
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