KVM: arm/arm64: Register ITS iodev when setting base address

We have to register the ITS iodevice before running the VM, because in
migration scenarios, we may be restoring a live device that wishes to
inject MSIs before the VCPUs have started.

All we need to register the ITS io device is the base address of the
ITS, so we can simply register that when the base address of the ITS is
set.

  [ Code to fix concurrency issues when setting the ITS base address and
    to fix the undef base address check written by Marc Zyngier ]
Signed-off-by: Christoffer Dall <cdall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

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

@@ -1540,14 +1540,19 @@ void vgic_enable_lpis(struct kvm_vcpu *vcpu)
 		its_sync_lpi_pending_table(vcpu);
 }
 
-static int vgic_register_its_iodev(struct kvm *kvm, struct vgic_its *its)
+static int vgic_register_its_iodev(struct kvm *kvm, struct vgic_its *its,
+				   u64 addr)
 {
 	struct vgic_io_device *iodev = &its->iodev;
 	int ret;
 
-	if (IS_VGIC_ADDR_UNDEF(its->vgic_its_base))
-		return -ENXIO;
+	mutex_lock(&kvm->slots_lock);
+	if (!IS_VGIC_ADDR_UNDEF(its->vgic_its_base)) {
+		ret = -EBUSY;
+		goto out;
+	}
 
+	its->vgic_its_base = addr;
 	iodev->regions = its_registers;
 	iodev->nr_regions = ARRAY_SIZE(its_registers);
 	kvm_iodevice_init(&iodev->dev, &kvm_io_gic_ops);
@@ -1555,9 +1560,9 @@ static int vgic_register_its_iodev(struct kvm *kvm, struct vgic_its *its)
 	iodev->base_addr = its->vgic_its_base;
 	iodev->iodev_type = IODEV_ITS;
 	iodev->its = its;
-	mutex_lock(&kvm->slots_lock);
 	ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, iodev->base_addr,
 				      KVM_VGIC_V3_ITS_SIZE, &iodev->dev);
+out:
 	mutex_unlock(&kvm->slots_lock);
 
 	return ret;
@@ -2384,9 +2389,7 @@ static int vgic_its_set_attr(struct kvm_device *dev,
 		if (ret)
 			return ret;
 
-		its->vgic_its_base = addr;
-
-		return 0;
+		return vgic_register_its_iodev(dev->kvm, its, addr);
 	}
 	case KVM_DEV_ARM_VGIC_GRP_CTRL: {
 		const struct vgic_its_abi *abi = vgic_its_get_abi(its);
@@ -2462,30 +2465,3 @@ int kvm_vgic_register_its_device(void)
 	return kvm_register_device_ops(&kvm_arm_vgic_its_ops,
 				       KVM_DEV_TYPE_ARM_VGIC_ITS);
 }
-
-/*
- * Registers all ITSes with the kvm_io_bus framework.
- * To follow the existing VGIC initialization sequence, this has to be
- * done as late as possible, just before the first VCPU runs.
- */
-int vgic_register_its_iodevs(struct kvm *kvm)
-{
-	struct kvm_device *dev;
-	int ret = 0;
-
-	list_for_each_entry(dev, &kvm->devices, vm_node) {
-		if (dev->ops != &kvm_arm_vgic_its_ops)
-			continue;
-
-		ret = vgic_register_its_iodev(kvm, dev->private);
-		if (ret)
-			return ret;
-		/*
-		 * We don't need to care about tearing down previously
-		 * registered ITSes, as the kvm_io_bus framework removes
-		 * them for us if the VM gets destroyed.
-		 */
-	}
-
-	return ret;
-}

virt/kvm/arm/vgic/vgic-v3.c

@@ -397,14 +397,6 @@ int vgic_v3_map_resources(struct kvm *kvm)
 		goto out;
 	}
 
-	if (vgic_has_its(kvm)) {
-		ret = vgic_register_its_iodevs(kvm);
-		if (ret) {
-			kvm_err("Unable to register VGIC ITS MMIO regions\n");
-			goto out;
-		}
-	}
-
 	dist->ready = true;
 
 out:

virt/kvm/arm/vgic/vgic.h

@@ -181,7 +181,6 @@ bool vgic_v3_check_base(struct kvm *kvm);
 void vgic_v3_load(struct kvm_vcpu *vcpu);
 void vgic_v3_put(struct kvm_vcpu *vcpu);
 
-int vgic_register_its_iodevs(struct kvm *kvm);
 bool vgic_has_its(struct kvm *kvm);
 int kvm_vgic_register_its_device(void);
 void vgic_enable_lpis(struct kvm_vcpu *vcpu);