KVM: arm64: vgic-v2: Add helper for legacy dist/cpuif base address setting

We carry a legacy interface to set the base addresses for GICv2.
As this is currently plumbed into the same handling code as
the modern interface, it limits the evolution we can make there.

Add a helper dedicated to this handling, with a view of maybe
removing this in the future.
Signed-off-by: Marc Zyngier <maz@kernel.org>

arch/arm64/kvm/arm.c

@@ -1414,18 +1414,11 @@ void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm,
 static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
 					struct kvm_arm_device_addr *dev_addr)
 {
-	unsigned long dev_id, type;
-
-	dev_id = (dev_addr->id & KVM_ARM_DEVICE_ID_MASK) >>
-		KVM_ARM_DEVICE_ID_SHIFT;
-	type = (dev_addr->id & KVM_ARM_DEVICE_TYPE_MASK) >>
-		KVM_ARM_DEVICE_TYPE_SHIFT;
-
-	switch (dev_id) {
+	switch (FIELD_GET(KVM_ARM_DEVICE_ID_MASK, dev_addr->id)) {
 	case KVM_ARM_DEVICE_VGIC_V2:
 		if (!vgic_present)
 			return -ENXIO;
-		return kvm_vgic_addr(kvm, type, &dev_addr->addr, true);
+		return kvm_set_legacy_vgic_v2_addr(kvm, dev_addr);
 	default:
 		return -ENODEV;
 	}

arch/arm64/kvm/vgic/vgic-kvm-device.c

@@ -41,6 +41,38 @@ static int vgic_check_type(struct kvm *kvm, int type_needed)
 		return 0;
 }
 
+int kvm_set_legacy_vgic_v2_addr(struct kvm *kvm, struct kvm_arm_device_addr *dev_addr)
+{
+	struct vgic_dist *vgic = &kvm->arch.vgic;
+	int r;
+
+	mutex_lock(&kvm->lock);
+	switch (FIELD_GET(KVM_ARM_DEVICE_TYPE_MASK, dev_addr->id)) {
+	case KVM_VGIC_V2_ADDR_TYPE_DIST:
+		r = vgic_check_type(kvm, KVM_DEV_TYPE_ARM_VGIC_V2);
+		if (!r)
+			r = vgic_check_iorange(kvm, vgic->vgic_dist_base, dev_addr->addr,
+					       SZ_4K, KVM_VGIC_V2_DIST_SIZE);
+		if (!r)
+			vgic->vgic_dist_base = dev_addr->addr;
+		break;
+	case KVM_VGIC_V2_ADDR_TYPE_CPU:
+		r = vgic_check_type(kvm, KVM_DEV_TYPE_ARM_VGIC_V2);
+		if (!r)
+			r = vgic_check_iorange(kvm, vgic->vgic_cpu_base, dev_addr->addr,
+					       SZ_4K, KVM_VGIC_V2_CPU_SIZE);
+		if (!r)
+			vgic->vgic_cpu_base = dev_addr->addr;
+		break;
+	default:
+		r = -ENODEV;
+	}
+
+	mutex_unlock(&kvm->lock);
+
+	return r;
+}
+
 /**
  * kvm_vgic_addr - set or get vgic VM base addresses
  * @kvm:   pointer to the vm struct

include/kvm/arm_vgic.h

@@ -365,6 +365,7 @@ extern struct static_key_false vgic_v2_cpuif_trap;
 extern struct static_key_false vgic_v3_cpuif_trap;
 
 int kvm_vgic_addr(struct kvm *kvm, unsigned long type, u64 *addr, bool write);
+int kvm_set_legacy_vgic_v2_addr(struct kvm *kvm, struct kvm_arm_device_addr *dev_addr);
 void kvm_vgic_early_init(struct kvm *kvm);
 int kvm_vgic_vcpu_init(struct kvm_vcpu *vcpu);
 int kvm_vgic_create(struct kvm *kvm, u32 type);