Ping On 3/20/19 3:12 PM, Suthikulpanit, Suravee wrote: > This reverts commit bb218fbcfaaa3b115d4cd7a43c0ca164f3a96e57. > > As Oren Twaig pointed out the old discussion: > > https://patchwork.kernel.org/patch/8292231/ > > that the change coud potentially cause an extra IPI to be sent to > the destination vcpu because the AVIC hardware already set the IRR bit > before the incomplete IPI #VMEXIT with id=1 (target vcpu is not running). > Since writting to ICR and ICR2 will also set the IRR. If something triggers > the destination vcpu to get scheduled before the emulation finishes, then > this could result in an additional IPI. > > Also, the issue mentioned in the commit bb218fbcfaaa was misdiagnosed. > > Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx> > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> > Reported-by: Oren Twaig <oren@xxxxxxxxxxx> > Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx> > --- > arch/x86/kvm/svm.c | 19 +++++++++++++++---- > 1 file changed, 15 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > index f13a3a24d360..47c4993448c7 100644 > --- a/arch/x86/kvm/svm.c > +++ b/arch/x86/kvm/svm.c > @@ -4512,14 +4512,25 @@ static int avic_incomplete_ipi_interception(struct vcpu_svm *svm) > kvm_lapic_reg_write(apic, APIC_ICR, icrl); > break; > case AVIC_IPI_FAILURE_TARGET_NOT_RUNNING: { > + int i; > + struct kvm_vcpu *vcpu; > + struct kvm *kvm = svm->vcpu.kvm; > struct kvm_lapic *apic = svm->vcpu.arch.apic; > > /* > - * Update ICR high and low, then emulate sending IPI, > - * which is handled when writing APIC_ICR. > + * At this point, we expect that the AVIC HW has already > + * set the appropriate IRR bits on the valid target > + * vcpus. So, we just need to kick the appropriate vcpu. > */ > - kvm_lapic_reg_write(apic, APIC_ICR2, icrh); > - kvm_lapic_reg_write(apic, APIC_ICR, icrl); > + kvm_for_each_vcpu(i, vcpu, kvm) { > + bool m = kvm_apic_match_dest(vcpu, apic, > + icrl & KVM_APIC_SHORT_MASK, > + GET_APIC_DEST_FIELD(icrh), > + icrl & KVM_APIC_DEST_MASK); > + > + if (m && !avic_vcpu_is_running(vcpu)) > + kvm_vcpu_wake_up(vcpu); > + } > break; > } > case AVIC_IPI_FAILURE_INVALID_TARGET: >
