From f7a14e06583456e470a4529c5ce849adb5051dbc Mon Sep 17 00:00:00 2001 From: "Suthikulpanit, Suravee" Date: Wed, 20 Mar 2019 08:12:28 +0000 Subject: [PATCH] Revert "svm: Fix AVIC incomplete IPI emulation" MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit This reverts commit c6f94dfcd9910e97e1bc79bd6bc48c715981795c. 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 c6f94dfcd991 was misdiagnosed. Cc: Radim Krčmář Cc: Paolo Bonzini Reported-by: Oren Twaig Signed-off-by: Suravee Suthikulpanit Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini --- 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 e0a791c3d4fcc..d7b14c9020526 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -4517,14 +4517,25 @@ 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: -- 2.39.5