| Message ID | 20210305021808.3769732-1-seanjc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86: Ensure deadline timer has truly expired before posting its IRQ | expand |
On 05/03/21 03:18, Sean Christopherson 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); > kvm_apic_inject_pending_timer_irqs(apic); > return; > } > Queued, thanks. Paolo
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
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); kvm_apic_inject_pending_timer_irqs(apic); return; }
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(-)