vfio: vfio_register_notifier: classify iommu notifier

Currently vfio_register_notifier assumes that there is only one
notifier chain, which is in vfio_iommu. However, the user might
also be interested in events other than vfio_iommu, for example,
vfio_group. Refactor vfio_{un}register_notifier implementation
to make it feasible.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Reviewed-by: Kirti Wankhede <kwankhede@nvidia.com>
Signed-off-by: Jike Song <jike.song@intel.com>
[aw: merge with commit 816ca69ea9c7 ("vfio: Fix handling of error returned by 'vfio_group_get_from_dev()'"), remove typedef]
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/vfio.c

@@ -2008,59 +2008,44 @@ err_unpin_pages:
 }
 EXPORT_SYMBOL(vfio_unpin_pages);
 
-int vfio_register_notifier(struct device *dev, struct notifier_block *nb)
+static int vfio_register_iommu_notifier(struct vfio_group *group,
+					unsigned long *events,
+					struct notifier_block *nb)
 {
 	struct vfio_container *container;
-	struct vfio_group *group;
 	struct vfio_iommu_driver *driver;
 	int ret;
 
-	if (!dev || !nb)
-		return -EINVAL;
-
-	group = vfio_group_get_from_dev(dev);
-	if (!group)
-		return -ENODEV;
-
 	ret = vfio_group_add_container_user(group);
 	if (ret)
-		goto err_register_nb;
+		return -EINVAL;
 
 	container = group->container;
 	down_read(&container->group_lock);
 
 	driver = container->iommu_driver;
 	if (likely(driver && driver->ops->register_notifier))
-		ret = driver->ops->register_notifier(container->iommu_data, nb);
+		ret = driver->ops->register_notifier(container->iommu_data,
+						     events, nb);
 	else
 		ret = -ENOTTY;
 
 	up_read(&container->group_lock);
 	vfio_group_try_dissolve_container(group);
 
-err_register_nb:
-	vfio_group_put(group);
 	return ret;
 }
-EXPORT_SYMBOL(vfio_register_notifier);
 
-int vfio_unregister_notifier(struct device *dev, struct notifier_block *nb)
+static int vfio_unregister_iommu_notifier(struct vfio_group *group,
+					  struct notifier_block *nb)
 {
 	struct vfio_container *container;
-	struct vfio_group *group;
 	struct vfio_iommu_driver *driver;
 	int ret;
 
-	if (!dev || !nb)
-		return -EINVAL;
-
-	group = vfio_group_get_from_dev(dev);
-	if (!group)
-		return -ENODEV;
-
 	ret = vfio_group_add_container_user(group);
 	if (ret)
-		goto err_unregister_nb;
+		return -EINVAL;
 
 	container = group->container;
 	down_read(&container->group_lock);
@@ -2075,7 +2060,56 @@ int vfio_unregister_notifier(struct device *dev, struct notifier_block *nb)
 	up_read(&container->group_lock);
 	vfio_group_try_dissolve_container(group);
 
-err_unregister_nb:
+	return ret;
+}
+
+int vfio_register_notifier(struct device *dev, enum vfio_notify_type type,
+			   unsigned long *events, struct notifier_block *nb)
+{
+	struct vfio_group *group;
+	int ret;
+
+	if (!dev || !nb || !events || (*events == 0))
+		return -EINVAL;
+
+	group = vfio_group_get_from_dev(dev);
+	if (!group)
+		return -ENODEV;
+
+	switch (type) {
+	case VFIO_IOMMU_NOTIFY:
+		ret = vfio_register_iommu_notifier(group, events, nb);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	vfio_group_put(group);
+	return ret;
+}
+EXPORT_SYMBOL(vfio_register_notifier);
+
+int vfio_unregister_notifier(struct device *dev, enum vfio_notify_type type,
+			     struct notifier_block *nb)
+{
+	struct vfio_group *group;
+	int ret;
+
+	if (!dev || !nb)
+		return -EINVAL;
+
+	group = vfio_group_get_from_dev(dev);
+	if (!group)
+		return -ENODEV;
+
+	switch (type) {
+	case VFIO_IOMMU_NOTIFY:
+		ret = vfio_unregister_iommu_notifier(group, nb);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
 	vfio_group_put(group);
 	return ret;
 }

drivers/vfio/vfio_iommu_type1.c

@@ -1584,10 +1584,18 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 }
 
 static int vfio_iommu_type1_register_notifier(void *iommu_data,
+					      unsigned long *events,
 					      struct notifier_block *nb)
 {
 	struct vfio_iommu *iommu = iommu_data;
 
+	/* clear known events */
+	*events &= ~VFIO_IOMMU_NOTIFY_DMA_UNMAP;
+
+	/* refuse to register if still events remaining */
+	if (*events)
+		return -EINVAL;
+
 	return blocking_notifier_chain_register(&iommu->notifier, nb);
 }
 

include/linux/vfio.h

@@ -81,6 +81,7 @@ struct vfio_iommu_driver_ops {
 	int		(*unpin_pages)(void *iommu_data,
 				       unsigned long *user_pfn, int npage);
 	int		(*register_notifier)(void *iommu_data,
+					     unsigned long *events,
 					     struct notifier_block *nb);
 	int		(*unregister_notifier)(void *iommu_data,
 					       struct notifier_block *nb);
@@ -107,12 +108,20 @@ extern int vfio_pin_pages(struct device *dev, unsigned long *user_pfn,
 extern int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn,
 			    int npage);
 
-#define VFIO_IOMMU_NOTIFY_DMA_UNMAP	(1)
+/* each type has independent events */
+enum vfio_notify_type {
+	VFIO_IOMMU_NOTIFY = 0,
+};
+
+/* events for VFIO_IOMMU_NOTIFY */
+#define VFIO_IOMMU_NOTIFY_DMA_UNMAP	BIT(0)
 
 extern int vfio_register_notifier(struct device *dev,
+				  enum vfio_notify_type type,
+				  unsigned long *required_events,
 				  struct notifier_block *nb);
-
 extern int vfio_unregister_notifier(struct device *dev,
+				    enum vfio_notify_type type,
 				    struct notifier_block *nb);
 
 /*