[RFC PATCH 6/8] svm: Temporary deactivate AVIC during ExtINT handling

["Suthikulpanit, Suravee" <Suravee.Suthikulpanit@amd.com>]

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.

Introduce svm_request_activate/deactivate_avic() helper functions,
which handle steps required to activate/deactivate AVIC.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
---
 arch/x86/kvm/svm.c | 57 +++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 54 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index a23b1e77acb6..580ab40ba207 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -383,6 +383,8 @@ static u8 rsm_ins_bytes[] = "\x0f\xaa";
 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_vcpu *vcpu);
 
 static int nested_svm_exit_handled(struct vcpu_svm *svm);
 static int nested_svm_intercept(struct vcpu_svm *svm);
@@ -2085,6 +2087,9 @@ static void avic_set_running(struct kvm_vcpu *vcpu, bool is_run)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 
+	if (!kvm_vcpu_apicv_active(vcpu))
+		return;
+
 	svm->avic_is_running = is_run;
 	if (is_run)
 		avic_vcpu_load(vcpu, vcpu->cpu);
@@ -2319,6 +2324,10 @@ static void svm_vcpu_blocking(struct kvm_vcpu *vcpu)
 
 static void svm_vcpu_unblocking(struct kvm_vcpu *vcpu)
 {
+	if (kvm_check_request(KVM_REQ_APICV_ACTIVATE, vcpu))
+		kvm_vcpu_activate_apicv(vcpu);
+	if (kvm_check_request(KVM_REQ_APICV_DEACTIVATE, vcpu))
+		kvm_vcpu_deactivate_apicv(vcpu);
 	avic_set_running(vcpu, true);
 }
 
@@ -4460,6 +4469,15 @@ 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))
+		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;
@@ -5150,6 +5168,34 @@ static void svm_hwapic_isr_update(struct kvm_vcpu *vcpu, int max_isr)
 {
 }
 
+static bool is_avic_active(struct vcpu_svm *svm)
+{
+	return (svm_get_enable_apicv(&svm->vcpu) &&
+		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;
+
+	avic_setup_access_page(vcpu, false);
+	kvm_make_apicv_activate_request(vcpu->kvm);
+}
+
+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;
+
+	avic_destroy_access_page(vcpu);
+	kvm_make_apicv_deactivate_request(vcpu->kvm);
+}
+
 /* Note: Currently only used by Hyper-V. */
 static void svm_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu)
 {
@@ -5437,9 +5483,6 @@ 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
@@ -5449,6 +5492,14 @@ 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);
 	}
-- 
2.17.1