Replace the full "kick" with just the "wake" in the fallback path when triggering a virtual interrupt via a posted interrupt fails because the guest is not IN_GUEST_MODE. If the guest transitions into guest mode between the check and the kick, then it's guaranteed to see the pending interrupt as KVM syncs the PIR to IRR (and onto GUEST_RVI) after setting IN_GUEST_MODE. Kicking the guest in this case is nothing more than an unnecessary VM-Exit (and host IRQ). Opportunistically update comments to explain the various ordering rules and barriers at play. Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> --- arch/x86/kvm/vmx/vmx.c | 4 ++-- arch/x86/kvm/x86.c | 9 +++++---- 2 files changed, 7 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 1b8804d93776..fa90eacbf7e2 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -3956,7 +3956,7 @@ static int vmx_deliver_nested_posted_interrupt(struct kvm_vcpu *vcpu, /* the PIR and ON have been set by L1. */ if (!kvm_vcpu_trigger_posted_interrupt(vcpu, true)) - kvm_vcpu_kick(vcpu); + kvm_vcpu_wake_up(vcpu); return 0; } return -1; @@ -3995,7 +3995,7 @@ static int vmx_deliver_posted_interrupt(struct kvm_vcpu *vcpu, int vector) */ if (vcpu != kvm_get_running_vcpu() && !kvm_vcpu_trigger_posted_interrupt(vcpu, false)) - kvm_vcpu_kick(vcpu); + kvm_vcpu_wake_up(vcpu); return 0; } diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 4a2341e4ff30..abf99b77883e 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9887,10 +9887,11 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) smp_mb__after_srcu_read_unlock(); /* - * This handles the case where a posted interrupt was - * notified with kvm_vcpu_kick. Assigned devices can - * use the POSTED_INTR_VECTOR even if APICv is disabled, - * so do it even if !kvm_vcpu_apicv_active(vcpu). + * Process pending posted interrupts to handle the case where the + * notification IRQ arrived in the host, or was never sent (because the + * target vCPU wasn't running). Do this regardless of the vCPU's APICv + * status, KVM doesn't update assigned devices when APICv is inhibited, + * i.e. they can post interrupts even if APICv is temporarily disabled. */ if (kvm_lapic_enabled(vcpu)) static_call_cond(kvm_x86_sync_pir_to_irr)(vcpu); -- 2.34.1.400.ga245620fadb-goog
