KVM: arm/arm64: vgic: Implement early VGIC init functionality

Implement early initialization for both the distributor and the CPU
interfaces.  The basic idea is that even though the VGIC is not
functional or not requested from user space, the critical path of the
run loop can still call VGIC functions that just won't do anything,
without them having to check additional initialization flags to ensure
they don't look at uninitialized data structures.
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <cdall@linaro.org>

virt/kvm/arm/vgic/vgic-init.c

@@ -24,7 +24,12 @@
 
 /*
  * Initialization rules: there are multiple stages to the vgic
- * initialization, both for the distributor and the CPU interfaces.
+ * initialization, both for the distributor and the CPU interfaces.  The basic
+ * idea is that even though the VGIC is not functional or not requested from
+ * user space, the critical path of the run loop can still call VGIC functions
+ * that just won't do anything, without them having to check additional
+ * initialization flags to ensure they don't look at uninitialized data
+ * structures.
  *
  * Distributor:
  *
@@ -39,23 +44,67 @@
  *
  * CPU Interface:
  *
- * - kvm_vgic_cpu_early_init(): initialization of static data that
+ * - kvm_vgic_vcpu_early_init(): initialization of static data that
  *   doesn't depend on any sizing information or emulation type. No
  *   allocation is allowed there.
  */
 
 /* EARLY INIT */
 
-/*
- * Those 2 functions should not be needed anymore but they
- * still are called from arm.c
+/**
+ * kvm_vgic_early_init() - Initialize static VGIC VCPU data structures
+ * @kvm: The VM whose VGIC districutor should be initialized
+ *
+ * Only do initialization of static structures that don't require any
+ * allocation or sizing information from userspace.  vgic_init() called
+ * kvm_vgic_dist_init() which takes care of the rest.
  */
 void kvm_vgic_early_init(struct kvm *kvm)
 {
+	struct vgic_dist *dist = &kvm->arch.vgic;
+
+	INIT_LIST_HEAD(&dist->lpi_list_head);
+	spin_lock_init(&dist->lpi_list_lock);
 }
 
+/**
+ * kvm_vgic_vcpu_early_init() - Initialize static VGIC VCPU data structures
+ * @vcpu: The VCPU whose VGIC data structures whould be initialized
+ *
+ * Only do initialization, but do not actually enable the VGIC CPU interface
+ * yet.
+ */
 void kvm_vgic_vcpu_early_init(struct kvm_vcpu *vcpu)
 {
+	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
+	int i;
+
+	INIT_LIST_HEAD(&vgic_cpu->ap_list_head);
+	spin_lock_init(&vgic_cpu->ap_list_lock);
+
+	/*
+	 * Enable and configure all SGIs to be edge-triggered and
+	 * configure all PPIs as level-triggered.
+	 */
+	for (i = 0; i < VGIC_NR_PRIVATE_IRQS; i++) {
+		struct vgic_irq *irq = &vgic_cpu->private_irqs[i];
+
+		INIT_LIST_HEAD(&irq->ap_list);
+		spin_lock_init(&irq->irq_lock);
+		irq->intid = i;
+		irq->vcpu = NULL;
+		irq->target_vcpu = vcpu;
+		irq->targets = 1U << vcpu->vcpu_id;
+		kref_init(&irq->refcount);
+		if (vgic_irq_is_sgi(i)) {
+			/* SGIs */
+			irq->enabled = 1;
+			irq->config = VGIC_CONFIG_EDGE;
+		} else {
+			/* PPIs */
+			irq->config = VGIC_CONFIG_LEVEL;
+		}
+	}
 }
 
 /* CREATION */
@@ -148,9 +197,6 @@ static int kvm_vgic_dist_init(struct kvm *kvm, unsigned int nr_spis)
 	struct kvm_vcpu *vcpu0 = kvm_get_vcpu(kvm, 0);
 	int i;
 
-	INIT_LIST_HEAD(&dist->lpi_list_head);
-	spin_lock_init(&dist->lpi_list_lock);
-
 	dist->spis = kcalloc(nr_spis, sizeof(struct vgic_irq), GFP_KERNEL);
 	if (!dist->spis)
 		return  -ENOMEM;
@@ -181,41 +227,11 @@ static int kvm_vgic_dist_init(struct kvm *kvm, unsigned int nr_spis)
 }
 
 /**
- * kvm_vgic_vcpu_init: initialize the vcpu data structures and
- * enable the VCPU interface
- * @vcpu: the VCPU which's VGIC should be initialized
+ * kvm_vgic_vcpu_init() - Enable the VCPU interface
+ * @vcpu: the VCPU which's VGIC should be enabled
  */
 static void kvm_vgic_vcpu_init(struct kvm_vcpu *vcpu)
 {
-	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
-	int i;
-
-	INIT_LIST_HEAD(&vgic_cpu->ap_list_head);
-	spin_lock_init(&vgic_cpu->ap_list_lock);
-
-	/*
-	 * Enable and configure all SGIs to be edge-triggered and
-	 * configure all PPIs as level-triggered.
-	 */
-	for (i = 0; i < VGIC_NR_PRIVATE_IRQS; i++) {
-		struct vgic_irq *irq = &vgic_cpu->private_irqs[i];
-
-		INIT_LIST_HEAD(&irq->ap_list);
-		spin_lock_init(&irq->irq_lock);
-		irq->intid = i;
-		irq->vcpu = NULL;
-		irq->target_vcpu = vcpu;
-		irq->targets = 1U << vcpu->vcpu_id;
-		kref_init(&irq->refcount);
-		if (vgic_irq_is_sgi(i)) {
-			/* SGIs */
-			irq->enabled = 1;
-			irq->config = VGIC_CONFIG_EDGE;
-		} else {
-			/* PPIs */
-			irq->config = VGIC_CONFIG_LEVEL;
-		}
-	}
 	if (kvm_vgic_global_state.type == VGIC_V2)
 		vgic_v2_enable(vcpu);
 	else