From: Greg Kroah-Hartman gregkh@linuxfoundation.org
From: Sean Christopherson seanjc@google.com
commit beda430177f56656e7980dcce93456ffaa35676b upstream.
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 Message-Id: 20210305021808.3769732-1-seanjc@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/lapic.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)
--- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -1641,7 +1641,16 @@ static void apic_timer_expired(struct kv }
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; }