From 31f251d4ddfa464c6dd92ee873b9b223e992a085 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 8 Dec 2021 01:52:20 +0000 Subject: KVM: SVM: Signal AVIC doorbell iff vCPU is in guest mode Signal the AVIC doorbell iff the vCPU is running in the guest. If the vCPU is not IN_GUEST_MODE, it's guaranteed to pick up any pending IRQs on the next VMRUN, which unconditionally processes the vIRR. Add comments to document the logic. Signed-off-by: Sean Christopherson Message-Id: <20211208015236.1616697-11-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm/avic.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c index 0e5b49294086..40039477bebb 100644 --- a/arch/x86/kvm/svm/avic.c +++ b/arch/x86/kvm/svm/avic.c @@ -672,9 +672,22 @@ int svm_deliver_avic_intr(struct kvm_vcpu *vcpu, int vec) return -1; kvm_lapic_set_irr(vec, vcpu->arch.apic); + + /* + * Pairs with the smp_mb_*() after setting vcpu->guest_mode in + * vcpu_enter_guest() to ensure the write to the vIRR is ordered before + * the read of guest_mode, which guarantees that either VMRUN will see + * and process the new vIRR entry, or that the below code will signal + * the doorbell if the vCPU is already running in the guest. + */ smp_mb__after_atomic(); - if (avic_vcpu_is_running(vcpu)) { + /* + * Signal the doorbell to tell hardware to inject the IRQ if the vCPU + * is in the guest. If the vCPU is not in the guest, hardware will + * automatically process AVIC interrupts at VMRUN. + */ + if (vcpu->mode == IN_GUEST_MODE) { int cpu = READ_ONCE(vcpu->cpu); /* @@ -688,8 +701,13 @@ int svm_deliver_avic_intr(struct kvm_vcpu *vcpu, int vec) if (cpu != get_cpu()) wrmsrl(SVM_AVIC_DOORBELL, kvm_cpu_get_apicid(cpu)); put_cpu(); - } else + } else { + /* + * Wake the vCPU if it was blocking. KVM will then detect the + * pending IRQ when checking if the vCPU has a wake event. + */ kvm_vcpu_wake_up(vcpu); + } return 0; } -- cgit v1.2.3