| Message ID | 1619608082-4187-1-git-send-email-wanpengli@tencent.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: LAPIC: Accurately guarantee busy wait for timer to expire when using hv_timer | expand |
On Wed, Apr 28, 2021, Wanpeng Li wrote: > 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) 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@google.com> > Signed-off-by: Wanpeng Li <wanpengli@tencent.com> Reviewed-by: Sean Christopherson <seanjc@google.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 >
On 29/04/21 00:56, Sean Christopherson wrote: > On Wed, Apr 28, 2021, Wanpeng Li wrote: >> 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) > > 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@google.com> >> Signed-off-by: Wanpeng Li <wanpengli@tencent.com> > > Reviewed-by: Sean Christopherson <seanjc@google.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 >> > Queued, thanks. Paolo
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);