KVM: SVM: Consolidate IRTE update when toggling AVIC on/off

Fold the IRTE modification logic in avic_refresh_apicv_exec_ctrl() into
__avic_vcpu_{load,put}(), and add a param to the helpers to communicate
whether or not AVIC is being toggled, i.e. if IRTE needs a "full" update,
or just a quick update to set the CPU and IsRun.

Link: https://lore.kernel.org/r/20250611224604.313496-61-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

arch/x86/kvm/svm/avic.c

@@ -811,7 +811,28 @@ int avic_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm,
 	return irq_set_vcpu_affinity(host_irq, NULL);
 }
 
-static void avic_update_iommu_vcpu_affinity(struct kvm_vcpu *vcpu, int cpu)
+enum avic_vcpu_action {
+	/*
+	 * There is no need to differentiate between activate and deactivate,
+	 * as KVM only refreshes AVIC state when the vCPU is scheduled in and
+	 * isn't blocking, i.e. the pCPU must always be (in)valid when AVIC is
+	 * being (de)activated.
+	 */
+	AVIC_TOGGLE_ON_OFF	= BIT(0),
+	AVIC_ACTIVATE		= AVIC_TOGGLE_ON_OFF,
+	AVIC_DEACTIVATE		= AVIC_TOGGLE_ON_OFF,
+
+	/*
+	 * No unique action is required to deal with a vCPU that stops/starts
+	 * running, as IRTEs are configured to generate GALog interrupts at all
+	 * times.
+	 */
+	AVIC_START_RUNNING	= 0,
+	AVIC_STOP_RUNNING	= 0,
+};
+
+static void avic_update_iommu_vcpu_affinity(struct kvm_vcpu *vcpu, int cpu,
+					    enum avic_vcpu_action action)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 	struct kvm_kernel_irqfd *irqfd;
@@ -825,11 +846,20 @@ static void avic_update_iommu_vcpu_affinity(struct kvm_vcpu *vcpu, int cpu)
 	if (list_empty(&svm->ir_list))
 		return;
 
-	list_for_each_entry(irqfd, &svm->ir_list, vcpu_list)
-		WARN_ON_ONCE(amd_iommu_update_ga(cpu, irqfd->irq_bypass_data));
+	list_for_each_entry(irqfd, &svm->ir_list, vcpu_list) {
+		void *data = irqfd->irq_bypass_data;
+
+		if (!(action & AVIC_TOGGLE_ON_OFF))
+			WARN_ON_ONCE(amd_iommu_update_ga(cpu, data));
+		else if (cpu >= 0)
+			WARN_ON_ONCE(amd_iommu_activate_guest_mode(data, cpu));
+		else
+			WARN_ON_ONCE(amd_iommu_deactivate_guest_mode(data));
+	}
 }
 
-static void __avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
+static void __avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu,
+			     enum avic_vcpu_action action)
 {
 	struct kvm_svm *kvm_svm = to_kvm_svm(vcpu->kvm);
 	int h_physical_id = kvm_cpu_get_apicid(cpu);
@@ -874,7 +904,7 @@ static void __avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 
 	WRITE_ONCE(kvm_svm->avic_physical_id_table[vcpu->vcpu_id], entry);
 
-	avic_update_iommu_vcpu_affinity(vcpu, h_physical_id);
+	avic_update_iommu_vcpu_affinity(vcpu, h_physical_id, action);
 
 	spin_unlock_irqrestore(&svm->ir_list_lock, flags);
 }
@@ -891,10 +921,10 @@ void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 	if (kvm_vcpu_is_blocking(vcpu))
 		return;
 
-	__avic_vcpu_load(vcpu, cpu);
+	__avic_vcpu_load(vcpu, cpu, AVIC_START_RUNNING);
 }
 
-static void __avic_vcpu_put(struct kvm_vcpu *vcpu)
+static void __avic_vcpu_put(struct kvm_vcpu *vcpu, enum avic_vcpu_action action)
 {
 	struct kvm_svm *kvm_svm = to_kvm_svm(vcpu->kvm);
 	struct vcpu_svm *svm = to_svm(vcpu);
@@ -916,7 +946,7 @@ static void __avic_vcpu_put(struct kvm_vcpu *vcpu)
 	 */
 	spin_lock_irqsave(&svm->ir_list_lock, flags);
 
-	avic_update_iommu_vcpu_affinity(vcpu, -1);
+	avic_update_iommu_vcpu_affinity(vcpu, -1, action);
 
 	entry &= ~AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;
 	svm->avic_physical_id_entry = entry;
@@ -942,7 +972,7 @@ void avic_vcpu_put(struct kvm_vcpu *vcpu)
 	if (!(entry & AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK))
 		return;
 
-	__avic_vcpu_put(vcpu);
+	__avic_vcpu_put(vcpu, AVIC_STOP_RUNNING);
 }
 
 void avic_refresh_virtual_apic_mode(struct kvm_vcpu *vcpu)
@@ -971,41 +1001,18 @@ void avic_refresh_virtual_apic_mode(struct kvm_vcpu *vcpu)
 
 void avic_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu)
 {
-	bool activated = kvm_vcpu_apicv_active(vcpu);
-	int apic_id = kvm_cpu_get_apicid(vcpu->cpu);
-	struct vcpu_svm *svm = to_svm(vcpu);
-	struct kvm_kernel_irqfd *irqfd;
-	unsigned long flags;
-
 	if (!enable_apicv)
 		return;
 
+	/* APICv should only be toggled on/off while the vCPU is running. */
+	WARN_ON_ONCE(kvm_vcpu_is_blocking(vcpu));
+
 	avic_refresh_virtual_apic_mode(vcpu);
 
-	if (activated)
-		__avic_vcpu_load(vcpu, vcpu->cpu);
+	if (kvm_vcpu_apicv_active(vcpu))
+		__avic_vcpu_load(vcpu, vcpu->cpu, AVIC_ACTIVATE);
 	else
-		__avic_vcpu_put(vcpu);
-
-	/*
-	 * Here, we go through the per-vcpu ir_list to update all existing
-	 * interrupt remapping table entry targeting this vcpu.
-	 */
-	spin_lock_irqsave(&svm->ir_list_lock, flags);
-
-	if (list_empty(&svm->ir_list))
-		goto out;
-
-	list_for_each_entry(irqfd, &svm->ir_list, vcpu_list) {
-		void *data = irqfd->irq_bypass_data;
-
-		if (activated)
-			WARN_ON_ONCE(amd_iommu_activate_guest_mode(data, apic_id));
-		else
-			WARN_ON_ONCE(amd_iommu_deactivate_guest_mode(data));
-	}
-out:
-	spin_unlock_irqrestore(&svm->ir_list_lock, flags);
+		__avic_vcpu_put(vcpu, AVIC_DEACTIVATE);
 }
 
 void avic_vcpu_blocking(struct kvm_vcpu *vcpu)
@@ -1031,7 +1038,7 @@ void avic_vcpu_blocking(struct kvm_vcpu *vcpu)
 	 * CPU and cause noisy neighbor problems if the VM is sending interrupts
 	 * to the vCPU while it's scheduled out.
 	 */
-	avic_vcpu_put(vcpu);
+	__avic_vcpu_put(vcpu, AVIC_STOP_RUNNING);
 }
 
 void avic_vcpu_unblocking(struct kvm_vcpu *vcpu)