Messages in this thread | | | From | Wanpeng Li <> | Date | Fri, 12 Mar 2021 09:05:34 +0800 | Subject | Re: [PATCH] KVM: x86: Ensure deadline timer has truly expired before posting its IRQ |
| |
On Fri, 5 Mar 2021 at 10:19, Sean Christopherson <seanjc@google.com> wrote: > > When posting a deadline timer interrupt, open code the checks guarding > __kvm_wait_lapic_expire() in order to skip the lapic_timer_int_injected() > check in kvm_wait_lapic_expire(). The injection check will always fail > since the interrupt has not yet be injected. Moving the call after > injection would also be wrong as that wouldn't actually delay delivery > of the IRQ if it is indeed sent via posted interrupt. > > Fixes: 010fd37fddf6 ("KVM: LAPIC: Reduce world switch latency caused by timer_advance_ns") > Cc: stable@vger.kernel.org > Signed-off-by: Sean Christopherson <seanjc@google.com> > --- > arch/x86/kvm/lapic.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index 45d40bfacb7c..cb8ebfaccfb6 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -1642,7 +1642,16 @@ static void apic_timer_expired(struct kvm_lapic *apic, bool from_timer_fn) > } > > if (kvm_use_posted_timer_interrupt(apic->vcpu)) { > - kvm_wait_lapic_expire(vcpu); > + /* > + * Ensure the guest's timer has truly expired before posting an > + * interrupt. Open code the relevant checks to avoid querying > + * lapic_timer_int_injected(), which will be false since the > + * interrupt isn't yet injected. Waiting until after injecting > + * is not an option since that won't help a posted interrupt. > + */ > + if (vcpu->arch.apic->lapic_timer.expired_tscdeadline && > + vcpu->arch.apic->lapic_timer.timer_advance_ns) > + __kvm_wait_lapic_expire(vcpu);
Thanks for the fixing.
Wanpeng
| |