vfio: Refactor vfio_device open and close

This refactor makes the vfio_device_open() to accept device, iommufd_ctx
pointer and kvm pointer. These parameters are generic items in today's
group path and future device cdev path. Caller of vfio_device_open()
should take care the necessary protections. e.g. the current group path
need to hold the group_lock to ensure the iommufd_ctx and kvm pointer are
valid.

This refactor also wraps the group spefcific codes in the device open and
close paths to be paired helpers like:

- vfio_device_group_open/close(): call vfio_device_open/close()
- vfio_device_group_use/unuse_iommu(): this pair is container specific.
				       iommufd vs. container is selected
				       in vfio_device_first_open().

Such helpers are supposed to be moved to group.c. While iommufd related
codes will be kept in the generic helpers since future device cdev path
also need to handle iommufd.

Link: https://lore.kernel.org/r/20221201145535.589687-8-yi.l.liu@intel.comReviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Tested-by: Lixiao Yang <lixiao.yang@intel.com>
Tested-by: Yu He <yu.he@intel.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/vfio/vfio_main.c

@@ -783,7 +783,38 @@ static bool vfio_assert_device_open(struct vfio_device *device)
 	return !WARN_ON_ONCE(!READ_ONCE(device->open_count));
 }
 
-static int vfio_device_first_open(struct vfio_device *device)
+static int vfio_device_group_use_iommu(struct vfio_device *device)
+{
+	struct vfio_group *group = device->group;
+	int ret = 0;
+
+	lockdep_assert_held(&group->group_lock);
+
+	if (WARN_ON(!group->container))
+		return -EINVAL;
+
+	ret = vfio_group_use_container(group);
+	if (ret)
+		return ret;
+	vfio_device_container_register(device);
+	return 0;
+}
+
+static void vfio_device_group_unuse_iommu(struct vfio_device *device)
+{
+	struct vfio_group *group = device->group;
+
+	lockdep_assert_held(&group->group_lock);
+
+	if (WARN_ON(!group->container))
+		return;
+
+	vfio_device_container_unregister(device);
+	vfio_group_unuse_container(group);
+}
+
+static int vfio_device_first_open(struct vfio_device *device,
+				  struct iommufd_ctx *iommufd, struct kvm *kvm)
 {
 	int ret;
 
@@ -792,77 +823,56 @@ static int vfio_device_first_open(struct vfio_device *device)
 	if (!try_module_get(device->dev->driver->owner))
 		return -ENODEV;
 
-	/*
-	 * Here we pass the KVM pointer with the group under the lock.  If the
-	 * device driver will use it, it must obtain a reference and release it
-	 * during close_device.
-	 */
-	mutex_lock(&device->group->group_lock);
-	if (!vfio_group_has_iommu(device->group)) {
-		ret = -EINVAL;
+	if (iommufd)
+		ret = vfio_iommufd_bind(device, iommufd);
+	else
+		ret = vfio_device_group_use_iommu(device);
+	if (ret)
 		goto err_module_put;
-	}
 
-	if (device->group->container) {
-		ret = vfio_group_use_container(device->group);
-		if (ret)
-			goto err_module_put;
-		vfio_device_container_register(device);
-	} else if (device->group->iommufd) {
-		ret = vfio_iommufd_bind(device, device->group->iommufd);
-		if (ret)
-			goto err_module_put;
-	}
-
-	device->kvm = device->group->kvm;
+	device->kvm = kvm;
 	if (device->ops->open_device) {
 		ret = device->ops->open_device(device);
 		if (ret)
-			goto err_container;
+			goto err_unuse_iommu;
 	}
-	mutex_unlock(&device->group->group_lock);
 	return 0;
 
-err_container:
+err_unuse_iommu:
 	device->kvm = NULL;
-	if (device->group->container) {
-		vfio_device_container_unregister(device);
-		vfio_group_unuse_container(device->group);
-	} else if (device->group->iommufd) {
+	if (iommufd)
 		vfio_iommufd_unbind(device);
-	}
+	else
+		vfio_device_group_unuse_iommu(device);
 err_module_put:
-	mutex_unlock(&device->group->group_lock);
 	module_put(device->dev->driver->owner);
 	return ret;
 }
 
-static void vfio_device_last_close(struct vfio_device *device)
+static void vfio_device_last_close(struct vfio_device *device,
+				   struct iommufd_ctx *iommufd)
 {
 	lockdep_assert_held(&device->dev_set->lock);
 
-	mutex_lock(&device->group->group_lock);
 	if (device->ops->close_device)
 		device->ops->close_device(device);
 	device->kvm = NULL;
-	if (device->group->container) {
-		vfio_device_container_unregister(device);
-		vfio_group_unuse_container(device->group);
-	} else if (device->group->iommufd) {
+	if (iommufd)
 		vfio_iommufd_unbind(device);
-	}
-	mutex_unlock(&device->group->group_lock);
+	else
+		vfio_device_group_unuse_iommu(device);
 	module_put(device->dev->driver->owner);
 }
 
-static int vfio_device_open(struct vfio_device *device)
+static int vfio_device_open(struct vfio_device *device,
+			    struct iommufd_ctx *iommufd, struct kvm *kvm)
 {
 	int ret = 0;
 
 	mutex_lock(&device->dev_set->lock);
 	device->open_count++;
 	if (device->open_count == 1) {
-		ret = vfio_device_first_open(device);
+		ret = vfio_device_first_open(device, iommufd, kvm);
 		if (ret)
 			device->open_count--;
 	}
@@ -871,22 +881,53 @@ static int vfio_device_open(struct vfio_device *device)
 	return ret;
 }
 
-static void vfio_device_close(struct vfio_device *device)
+static void vfio_device_close(struct vfio_device *device,
+			      struct iommufd_ctx *iommufd)
 {
 	mutex_lock(&device->dev_set->lock);
 	vfio_assert_device_open(device);
 	if (device->open_count == 1)
-		vfio_device_last_close(device);
+		vfio_device_last_close(device, iommufd);
 	device->open_count--;
 	mutex_unlock(&device->dev_set->lock);
 }
 
+static int vfio_device_group_open(struct vfio_device *device)
+{
+	int ret;
+
+	mutex_lock(&device->group->group_lock);
+	if (!vfio_group_has_iommu(device->group)) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	/*
+	 * Here we pass the KVM pointer with the group under the lock.  If the
+	 * device driver will use it, it must obtain a reference and release it
+	 * during close_device.
+	 */
+	ret = vfio_device_open(device, device->group->iommufd,
+			       device->group->kvm);
+
+out_unlock:
+	mutex_unlock(&device->group->group_lock);
+	return ret;
+}
+
+static void vfio_device_group_close(struct vfio_device *device)
+{
+	mutex_lock(&device->group->group_lock);
+	vfio_device_close(device, device->group->iommufd);
+	mutex_unlock(&device->group->group_lock);
+}
+
 static struct file *vfio_device_open_file(struct vfio_device *device)
 {
 	struct file *filep;
 	int ret;
 
-	ret = vfio_device_open(device);
+	ret = vfio_device_group_open(device);
 	if (ret)
 		goto err_out;
 
@@ -918,7 +959,7 @@ static struct file *vfio_device_open_file(struct vfio_device *device)
 	return filep;
 
 err_close_device:
-	vfio_device_close(device);
+	vfio_device_group_close(device);
 err_out:
 	return ERR_PTR(ret);
 }
@@ -1130,7 +1171,7 @@ static int vfio_device_fops_release(struct inode *inode, struct file *filep)
 {
 	struct vfio_device *device = filep->private_data;
 
-	vfio_device_close(device);
+	vfio_device_group_close(device);
 
 	vfio_device_put_registration(device);