On 29/04/21 00:56, Sean Christopherson wrote:
On Wed, Apr 28, 2021, Wanpeng Li wrote:
From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
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)
Well that's embarassing. I suspect/hope I tested the case where start_hv_timer()
detects the timer already expired. On the plus side, start_hv_timer() calls
cancel_hv_timer() after apic_timer_expired(), so there are unlikely to be hidden
side effects (and cancel_hv_timer() is tiny).
Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
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
Queued, thanks.
Paolo
