vdpa: Enable a user to add and delete a vdpa device

Add the ability to add and delete a vdpa device.

Examples:
Create a vdpa device of type network named "foo2" from
the management device vdpasim:

$ vdpa dev add mgmtdev vdpasim_net name foo2

Delete the vdpa device after its use:
$ vdpa dev del foo2

Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Eli Cohen <elic@nvidia.com>
Reviewed-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20210105103203.82508-5-parav@nvidia.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/vdpa.c

@@ -136,6 +136,37 @@ static int vdpa_name_match(struct device *dev, const void *data)
 	return (strcmp(dev_name(&vdev->dev), data) == 0);
 }
 
+static int __vdpa_register_device(struct vdpa_device *vdev)
+{
+	struct device *dev;
+
+	lockdep_assert_held(&vdpa_dev_mutex);
+	dev = bus_find_device(&vdpa_bus, NULL, dev_name(&vdev->dev), vdpa_name_match);
+	if (dev) {
+		put_device(dev);
+		return -EEXIST;
+	}
+	return device_add(&vdev->dev);
+}
+
+/**
+ * _vdpa_register_device - register a vDPA device with vdpa lock held
+ * Caller must have a succeed call of vdpa_alloc_device() before.
+ * Caller must invoke this routine in the management device dev_add()
+ * callback after setting up valid mgmtdev for this vdpa device.
+ * @vdev: the vdpa device to be registered to vDPA bus
+ *
+ * Returns an error when fail to add device to vDPA bus
+ */
+int _vdpa_register_device(struct vdpa_device *vdev)
+{
+	if (!vdev->mdev)
+		return -EINVAL;
+
+	return __vdpa_register_device(vdev);
+}
+EXPORT_SYMBOL_GPL(_vdpa_register_device);
+
 /**
  * vdpa_register_device - register a vDPA device
  * Callers must have a succeed call of vdpa_alloc_device() before.
@@ -145,24 +176,29 @@ static int vdpa_name_match(struct device *dev, const void *data)
  */
 int vdpa_register_device(struct vdpa_device *vdev)
 {
-	struct device *dev;
 	int err;
 
 	mutex_lock(&vdpa_dev_mutex);
-	dev = bus_find_device(&vdpa_bus, NULL, dev_name(&vdev->dev), vdpa_name_match);
+	err = __vdpa_register_device(vdev);
-	if (dev) {
-		put_device(dev);
-		err = -EEXIST;
-		goto name_err;
-	}
-
-	err = device_add(&vdev->dev);
-name_err:
 	mutex_unlock(&vdpa_dev_mutex);
 	return err;
 }
 EXPORT_SYMBOL_GPL(vdpa_register_device);
 
+/**
+ * _vdpa_unregister_device - unregister a vDPA device
+ * Caller must invoke this routine as part of management device dev_del()
+ * callback.
+ * @vdev: the vdpa device to be unregisted from vDPA bus
+ */
+void _vdpa_unregister_device(struct vdpa_device *vdev)
+{
+	lockdep_assert_held(&vdpa_dev_mutex);
+	WARN_ON(!vdev->mdev);
+	device_unregister(&vdev->dev);
+}
+EXPORT_SYMBOL_GPL(_vdpa_unregister_device);
+
 /**
  * vdpa_unregister_device - unregister a vDPA device
  * @vdev: the vdpa device to be unregisted from vDPA bus
@@ -221,10 +257,25 @@ int vdpa_mgmtdev_register(struct vdpa_mgmt_dev *mdev)
 }
 EXPORT_SYMBOL_GPL(vdpa_mgmtdev_register);
 
+static int vdpa_match_remove(struct device *dev, void *data)
+{
+	struct vdpa_device *vdev = container_of(dev, struct vdpa_device, dev);
+	struct vdpa_mgmt_dev *mdev = vdev->mdev;
+
+	if (mdev == data)
+		mdev->ops->dev_del(mdev, vdev);
+	return 0;
+}
+
 void vdpa_mgmtdev_unregister(struct vdpa_mgmt_dev *mdev)
 {
 	mutex_lock(&vdpa_dev_mutex);
+
 	list_del(&mdev->list);
+
+	/* Filter out all the entries belong to this management device and delete it. */
+	bus_for_each_dev(&vdpa_bus, NULL, mdev, vdpa_match_remove);
+
 	mutex_unlock(&vdpa_dev_mutex);
 }
 EXPORT_SYMBOL_GPL(vdpa_mgmtdev_unregister);
@@ -368,9 +419,69 @@ out:
 	return msg->len;
 }
 
+static int vdpa_nl_cmd_dev_add_set_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct vdpa_mgmt_dev *mdev;
+	const char *name;
+	int err = 0;
+
+	if (!info->attrs[VDPA_ATTR_DEV_NAME])
+		return -EINVAL;
+
+	name = nla_data(info->attrs[VDPA_ATTR_DEV_NAME]);
+
+	mutex_lock(&vdpa_dev_mutex);
+	mdev = vdpa_mgmtdev_get_from_attr(info->attrs);
+	if (IS_ERR(mdev)) {
+		NL_SET_ERR_MSG_MOD(info->extack, "Fail to find the specified management device");
+		err = PTR_ERR(mdev);
+		goto err;
+	}
+
+	err = mdev->ops->dev_add(mdev, name);
+err:
+	mutex_unlock(&vdpa_dev_mutex);
+	return err;
+}
+
+static int vdpa_nl_cmd_dev_del_set_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct vdpa_mgmt_dev *mdev;
+	struct vdpa_device *vdev;
+	struct device *dev;
+	const char *name;
+	int err = 0;
+
+	if (!info->attrs[VDPA_ATTR_DEV_NAME])
+		return -EINVAL;
+	name = nla_data(info->attrs[VDPA_ATTR_DEV_NAME]);
+
+	mutex_lock(&vdpa_dev_mutex);
+	dev = bus_find_device(&vdpa_bus, NULL, name, vdpa_name_match);
+	if (!dev) {
+		NL_SET_ERR_MSG_MOD(info->extack, "device not found");
+		err = -ENODEV;
+		goto dev_err;
+	}
+	vdev = container_of(dev, struct vdpa_device, dev);
+	if (!vdev->mdev) {
+		NL_SET_ERR_MSG_MOD(info->extack, "Only user created device can be deleted by user");
+		err = -EINVAL;
+		goto mdev_err;
+	}
+	mdev = vdev->mdev;
+	mdev->ops->dev_del(mdev, vdev);
+mdev_err:
+	put_device(dev);
+dev_err:
+	mutex_unlock(&vdpa_dev_mutex);
+	return err;
+}
+
 static const struct nla_policy vdpa_nl_policy[VDPA_ATTR_MAX + 1] = {
 	[VDPA_ATTR_MGMTDEV_BUS_NAME] = { .type = NLA_NUL_STRING },
 	[VDPA_ATTR_MGMTDEV_DEV_NAME] = { .type = NLA_STRING },
+	[VDPA_ATTR_DEV_NAME] = { .type = NLA_STRING },
 };
 
 static const struct genl_ops vdpa_nl_ops[] = {
@@ -380,6 +491,18 @@ static const struct genl_ops vdpa_nl_ops[] = {
 		.doit = vdpa_nl_cmd_mgmtdev_get_doit,
 		.dumpit = vdpa_nl_cmd_mgmtdev_get_dumpit,
 	},
+	{
+		.cmd = VDPA_CMD_DEV_NEW,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit = vdpa_nl_cmd_dev_add_set_doit,
+		.flags = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd = VDPA_CMD_DEV_DEL,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit = vdpa_nl_cmd_dev_del_set_doit,
+		.flags = GENL_ADMIN_PERM,
+	},
 };
 
 static struct genl_family vdpa_nl_family __ro_after_init = {

include/linux/vdpa.h

@@ -45,6 +45,8 @@ struct vdpa_mgmt_dev;
  * @index: device index
  * @features_valid: were features initialized? for legacy guests
  * @nvqs: maximum number of supported virtqueues
+ * @mdev: management device pointer; caller must setup when registering device as part
+ *	  of dev_add() mgmtdev ops callback before invoking _vdpa_register_device().
  */
 struct vdpa_device {
 	struct device dev;
@@ -53,6 +55,7 @@ struct vdpa_device {
 	unsigned int index;
 	bool features_valid;
 	int nvqs;
+	struct vdpa_mgmt_dev *mdev;
 };
 
 /**
@@ -260,6 +263,9 @@ struct vdpa_device *__vdpa_alloc_device(struct device *parent,
 int vdpa_register_device(struct vdpa_device *vdev);
 void vdpa_unregister_device(struct vdpa_device *vdev);
 
+int _vdpa_register_device(struct vdpa_device *vdev);
+void _vdpa_unregister_device(struct vdpa_device *vdev);
+
 /**
  * vdpa_driver - operations for a vDPA driver
  * @driver: underlying device driver

include/uapi/linux/vdpa.h

@@ -14,6 +14,8 @@ enum vdpa_command {
 	VDPA_CMD_UNSPEC,
 	VDPA_CMD_MGMTDEV_NEW,
 	VDPA_CMD_MGMTDEV_GET,		/* can dump */
+	VDPA_CMD_DEV_NEW,
+	VDPA_CMD_DEV_DEL,
 };
 
 enum vdpa_attr {
@@ -24,6 +26,8 @@ enum vdpa_attr {
 	VDPA_ATTR_MGMTDEV_DEV_NAME,		/* string */
 	VDPA_ATTR_MGMTDEV_SUPPORTED_CLASSES,	/* u64 */
 
+	VDPA_ATTR_DEV_NAME,			/* string */
+
 	/* new attributes must be added above here */
 	VDPA_ATTR_MAX,
 };