[PATCH v2 11/15] svm: Temporary deactivate AVIC during ExtINT handling

["Suthikulpanit, Suravee" <Suravee.Suthikulpanit@xxxxxxx>]

AMD AVIC does not support ExtINT. Therefore, AVIC must be temporary
deactivated and fall back to using legacy interrupt injection via vINTR
and interrupt window.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
---
 arch/x86/kvm/svm.c | 49 +++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 45 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index cfa4b13..4690351 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -384,6 +384,7 @@ struct amd_svm_iommu_ir {
 static void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);
 static void svm_flush_tlb(struct kvm_vcpu *vcpu, bool invalidate_gpa);
 static void svm_complete_interrupts(struct vcpu_svm *svm);
+static void svm_request_activate_avic(struct kvm_vcpu *vcpu);
 static bool svm_get_enable_apicv(struct kvm *kvm);
 static inline void avic_post_state_restore(struct kvm_vcpu *vcpu);
 
@@ -4494,6 +4495,15 @@ static int interrupt_window_interception(struct vcpu_svm *svm)
 {
 	kvm_make_request(KVM_REQ_EVENT, &svm->vcpu);
 	svm_clear_vintr(svm);
+
+	/*
+	 * For AVIC, the only reason to end up here is ExtINTs.
+	 * In this case AVIC was temporarily disabled for
+	 * requesting the IRQ window and we have to re-enable it.
+	 */
+	if (svm_get_enable_apicv(svm->vcpu.kvm))
+		svm_request_activate_avic(&svm->vcpu);
+
 	svm->vmcb->control.int_ctl &= ~V_IRQ_MASK;
 	mark_dirty(svm->vmcb, VMCB_INTR);
 	++svm->vcpu.stat.irq_window_exits;
@@ -5181,7 +5191,33 @@ static void svm_hwapic_isr_update(struct kvm_vcpu *vcpu, int max_isr)
 {
 }
 
-/* Note: Currently only used by Hyper-V. */
+static bool is_avic_active(struct vcpu_svm *svm)
+{
+	return (svm_get_enable_apicv(svm->vcpu.kvm) &&
+		svm->vmcb->control.int_ctl & AVIC_ENABLE_MASK);
+}
+
+static void svm_request_activate_avic(struct kvm_vcpu *vcpu)
+{
+	struct vcpu_svm *svm = to_svm(vcpu);
+
+	if (!lapic_in_kernel(vcpu) || is_avic_active(svm))
+		return;
+
+	kvm_make_apicv_activate_request(vcpu);
+}
+
+static void svm_request_deactivate_avic(struct kvm_vcpu *vcpu)
+{
+	struct vcpu_svm *svm = to_svm(vcpu);
+
+	if (!lapic_in_kernel(vcpu) || !is_avic_active(svm))
+		return;
+
+	/* Request temporary deactivate apicv */
+	kvm_make_apicv_deactivate_request(vcpu, false);
+}
+
 static void svm_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
@@ -5522,9 +5558,6 @@ static void enable_irq_window(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 
-	if (kvm_vcpu_apicv_active(vcpu))
-		return;
-
 	/*
 	 * In case GIF=0 we can't rely on the CPU to tell us when GIF becomes
 	 * 1, because that's a separate STGI/VMRUN intercept.  The next time we
@@ -5534,6 +5567,14 @@ static void enable_irq_window(struct kvm_vcpu *vcpu)
 	 * window under the assumption that the hardware will set the GIF.
 	 */
 	if ((vgif_enabled(svm) || gif_set(svm)) && nested_svm_intr(svm)) {
+		/*
+		 * IRQ window is not needed when AVIC is enabled,
+		 * unless we have pending ExtINT since it cannot be injected
+		 * via AVIC. In such case, we need to temporarily disable AVIC,
+		 * and fallback to injecting IRQ via V_IRQ.
+		 */
+		if (kvm_vcpu_apicv_active(vcpu))
+			svm_request_deactivate_avic(&svm->vcpu);
 		svm_set_vintr(svm);
 		svm_inject_irq(svm, 0x0);
 	}
-- 
1.8.3.1