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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, 2021-10-08 at 19:12 -0700, Sean Christopherson wrote: > 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 > --- > arch/x86/kvm/svm/avic.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c > index 208c5c71e827..cbf02e7e20d0 100644 > --- a/arch/x86/kvm/svm/avic.c > +++ b/arch/x86/kvm/svm/avic.c > @@ -674,7 +674,12 @@ int svm_deliver_avic_intr(struct kvm_vcpu *vcpu, int vec) > kvm_lapic_set_irr(vec, vcpu->arch.apic); > 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); > > /* > @@ -687,8 +692,13 @@ 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; > } It makes sense indeed to avoid ringing the doorbell when the vCPU is not in the guest mode. I do wonder if we want to call kvm_vcpu_wake_up always otherwise, as the vCPU might be just outside of the guest mode and not scheduled out. I don't know how expensive is kvm_vcpu_wake_up in this case. Before this patch, the avic_vcpu_is_running would only be false when the vCPU is scheduled out (e.g when vcpu_put was done on it) Best regards, Maxim Levitsky _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel