KVM: arm-vgic: Support KVM_CREATE_DEVICE for VGIC

Support creating the ARM VGIC device through the KVM_CREATE_DEVICE
ioctl, which can then later be leveraged to use the
KVM_{GET/SET}_DEVICE_ATTR, which is useful both for setting addresses in
a more generic API than the ARM-specific one and is useful for
save/restore of VGIC state.

Adds KVM_CAP_DEVICE_CTRL to ARM capabilities.

Note that we change the check for creating a VGIC from bailing out if
any VCPUs were created, to bailing out if any VCPUs were ever run.  This
is an important distinction that shouldn't break anything, but allows
creating the VGIC after the VCPUs have been created.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

Documentation/virtual/kvm/devices/arm-vgic.txt

@@ -0,0 +1,10 @@
+ARM Virtual Generic Interrupt Controller (VGIC)
+===============================================
+
+Device types supported:
+  KVM_DEV_TYPE_ARM_VGIC_V2     ARM Generic Interrupt Controller v2.0
+
+Only one VGIC instance may be instantiated through either this API or the
+legacy KVM_CREATE_IRQCHIP api.  The created VGIC will act as the VM interrupt
+controller, requiring emulated user-space devices to inject interrupts to the
+VGIC instead of directly to CPUs.

arch/arm/kvm/arm.c

@@ -190,6 +190,7 @@ int kvm_dev_ioctl_check_extension(long ext)
 	case KVM_CAP_IRQCHIP:
 		r = vgic_present;
 		break;
+	case KVM_CAP_DEVICE_CTRL:
 	case KVM_CAP_USER_MEMORY:
 	case KVM_CAP_SYNC_MMU:
 	case KVM_CAP_DESTROY_MEMORY_REGION_WORKS:

include/linux/kvm_host.h

@@ -1075,6 +1075,7 @@ struct kvm_device *kvm_device_from_filp(struct file *filp);
 extern struct kvm_device_ops kvm_mpic_ops;
 extern struct kvm_device_ops kvm_xics_ops;
 extern struct kvm_device_ops kvm_vfio_ops;
+extern struct kvm_device_ops kvm_arm_vgic_v2_ops;
 
 #ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
 

include/uapi/linux/kvm.h

@@ -853,6 +853,7 @@ struct kvm_device_attr {
 #define  KVM_DEV_VFIO_GROUP			1
 #define   KVM_DEV_VFIO_GROUP_ADD			1
 #define   KVM_DEV_VFIO_GROUP_DEL			2
+#define KVM_DEV_TYPE_ARM_VGIC_V2	5
 
 /*
  * ioctls for VM fds

virt/kvm/arm/vgic.c

@@ -1433,20 +1433,45 @@ out:
 
 int kvm_vgic_create(struct kvm *kvm)
 {
-	int ret = 0;
+	int i, vcpu_lock_idx = -1, ret = 0;
+	struct kvm_vcpu *vcpu;
 
 	mutex_lock(&kvm->lock);
 
-	if (atomic_read(&kvm->online_vcpus) || kvm->arch.vgic.vctrl_base) {
+	if (kvm->arch.vgic.vctrl_base) {
 		ret = -EEXIST;
 		goto out;
 	}
 
+	/*
+	 * Any time a vcpu is run, vcpu_load is called which tries to grab the
+	 * vcpu->mutex.  By grabbing the vcpu->mutex of all VCPUs we ensure
+	 * that no other VCPUs are run while we create the vgic.
+	 */
+	kvm_for_each_vcpu(i, vcpu, kvm) {
+		if (!mutex_trylock(&vcpu->mutex))
+			goto out_unlock;
+		vcpu_lock_idx = i;
+	}
+
+	kvm_for_each_vcpu(i, vcpu, kvm) {
+		if (vcpu->arch.has_run_once) {
+			ret = -EBUSY;
+			goto out_unlock;
+		}
+	}
+
 	spin_lock_init(&kvm->arch.vgic.lock);
 	kvm->arch.vgic.vctrl_base = vgic_vctrl_base;
 	kvm->arch.vgic.vgic_dist_base = VGIC_ADDR_UNDEF;
 	kvm->arch.vgic.vgic_cpu_base = VGIC_ADDR_UNDEF;
 
+out_unlock:
+	for (; vcpu_lock_idx >= 0; vcpu_lock_idx--) {
+		vcpu = kvm_get_vcpu(kvm, vcpu_lock_idx);
+		mutex_unlock(&vcpu->mutex);
+	}
+
 out:
 	mutex_unlock(&kvm->lock);
 	return ret;
@@ -1510,3 +1535,37 @@ int kvm_vgic_set_addr(struct kvm *kvm, unsigned long type, u64 addr)
 	mutex_unlock(&kvm->lock);
 	return r;
 }
+
+static int vgic_set_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
+{
+	return -ENXIO;
+}
+
+static int vgic_get_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
+{
+	return -ENXIO;
+}
+
+static int vgic_has_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
+{
+	return -ENXIO;
+}
+
+static void vgic_destroy(struct kvm_device *dev)
+{
+	kfree(dev);
+}
+
+static int vgic_create(struct kvm_device *dev, u32 type)
+{
+	return kvm_vgic_create(dev->kvm);
+}
+
+struct kvm_device_ops kvm_arm_vgic_v2_ops = {
+	.name = "kvm-arm-vgic",
+	.create = vgic_create,
+	.destroy = vgic_destroy,
+	.set_attr = vgic_set_attr,
+	.get_attr = vgic_get_attr,
+	.has_attr = vgic_has_attr,
+};

virt/kvm/kvm_main.c

@@ -2272,6 +2272,11 @@ static int kvm_ioctl_create_device(struct kvm *kvm,
 	case KVM_DEV_TYPE_VFIO:
 		ops = &kvm_vfio_ops;
 		break;
+#endif
+#ifdef CONFIG_KVM_ARM_VGIC
+	case KVM_DEV_TYPE_ARM_VGIC_V2:
+		ops = &kvm_arm_vgic_v2_ops;
+		break;
 #endif
 	default:
 		return -ENODEV;