Re: [PATCH v14 12/22] vfio: Add notifier callback to parent's ops structure of mdev

[Kirti Wankhede]

Add a notifier calback to parent's ops structure of mdev device so that per
device notifer for vfio module is registered through vfio_mdev module.

Signed-off-by: Kirti Wankhede <kwankhede@xxxxxxxxxx>
Signed-off-by: Neo Jia <cjia@xxxxxxxxxx>
Change-Id: Iafa6f1721aecdd6e50eb93b153b5621e6d29b637
---
 drivers/vfio/mdev/vfio_mdev.c | 32 +++++++++++++++++++++++++++++++-
 include/linux/mdev.h          |  9 +++++++++
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/mdev/vfio_mdev.c b/drivers/vfio/mdev/vfio_mdev.c
index ffc36758cb84..7ffdc317319d 100644
--- a/drivers/vfio/mdev/vfio_mdev.c
+++ b/drivers/vfio/mdev/vfio_mdev.c
@@ -24,6 +24,15 @@
 #define DRIVER_AUTHOR   "NVIDIA Corporation"
 #define DRIVER_DESC     "VFIO based driver for Mediated device"
 
+static int vfio_mdev_notifier(struct notifier_block *nb, unsigned long action,
+			      void *data)
+{
+	struct mdev_device *mdev = container_of(nb, struct mdev_device, nb);
+	struct parent_device *parent = mdev->parent;
+
+	return parent->ops->notifier(mdev, action, data);
+}
+
 static int vfio_mdev_open(void *device_data)
 {
 	struct mdev_device *mdev = device_data;
@@ -36,9 +45,27 @@ static int vfio_mdev_open(void *device_data)
 	if (!try_module_get(THIS_MODULE))
 		return -ENODEV;
 
+	if (likely(parent->ops->notifier)) {
+		mdev->nb.notifier_call = vfio_mdev_notifier;
+		ret = vfio_register_notifier(&mdev->dev, &mdev->nb);
+
+		/*
+		 * This should not fail if backend iommu module doesn't support
+		 * register_notifier.
+		 */
+		if (ret && (ret != -ENOTTY)) {
+			pr_err("Failed to register notifier for mdev\n");
+			module_put(THIS_MODULE);
+			return ret;
+		}
+	}
+
 	ret = parent->ops->open(mdev);
-	if (ret)
+	if (ret) {
+		if (likely(parent->ops->notifier))
+			vfio_unregister_notifier(&mdev->dev, &mdev->nb);
 		module_put(THIS_MODULE);
+	}
 
 	return ret;
 }
@@ -51,6 +78,9 @@ static void vfio_mdev_release(void *device_data)
 	if (likely(parent->ops->release))
 		parent->ops->release(mdev);
 
+	if (likely(parent->ops->notifier))
+		vfio_unregister_notifier(&mdev->dev, &mdev->nb);
+
 	module_put(THIS_MODULE);
 }
 
diff --git a/include/linux/mdev.h b/include/linux/mdev.h
index ec819e9a115a..94c43034c297 100644
--- a/include/linux/mdev.h
+++ b/include/linux/mdev.h
@@ -37,6 +37,7 @@ struct mdev_device {
 	struct kref		ref;
 	struct list_head	next;
 	struct kobject		*type_kobj;
+	struct notifier_block	nb;
 };
 
 /**
@@ -85,6 +86,12 @@ struct mdev_device {
  * @mmap:		mmap callback
  *			@mdev: mediated device structure
  *			@vma: vma structure
+ * @notifer:		Notifier callback, currently only for
+ *			VFIO_IOMMU_NOTIFY_DMA_UNMAP action notified duing
+ *			DMA_UNMAP call on mapped iova range.
+ *			@mdev: mediated device structure
+ *			@action: Action for which notifier is called
+ *			@data: Data associated with the notifier
  * Parent device that support mediated device should be registered with mdev
  * module with parent_ops structure.
  **/
@@ -106,6 +113,8 @@ struct parent_ops {
 	ssize_t (*ioctl)(struct mdev_device *mdev, unsigned int cmd,
 			 unsigned long arg);
 	int	(*mmap)(struct mdev_device *mdev, struct vm_area_struct *vma);
+	int	(*notifier)(struct mdev_device *mdev, unsigned long action,
+			    void *data);
 };
 
 /* interface for exporting mdev supported type attributes */
-- 
2.7.0