On 1/26/2018 8:58 AM, Michael S. Tsirkin wrote:

On Thu, Jan 11, 2018 at 09:58:39PM -0800, Sridhar Samudrala wrote:

quoted

@@ -2859,6 +3123,42 @@ static struct virtio_driver virtio_net_driver = {
  #endif
  };
  
+static int virtio_netdev_event(struct notifier_block *this,
+			       unsigned long event, void *ptr)
+{
+	struct net_device *event_dev = netdev_notifier_info_to_dev(ptr);
+
+	/* Skip our own events */
+	if (event_dev->netdev_ops == &virtnet_netdev)
+		return NOTIFY_DONE;
+
+	/* Avoid non-Ethernet type devices */
+	if (event_dev->type != ARPHRD_ETHER)
+		return NOTIFY_DONE;
+
+	/* Avoid Vlan dev with same MAC registering as VF */
+	if (is_vlan_dev(event_dev))
+		return NOTIFY_DONE;
+
+	/* Avoid Bonding master dev with same MAC registering as VF */
+	if ((event_dev->priv_flags & IFF_BONDING) &&
+	    (event_dev->flags & IFF_MASTER))
+		return NOTIFY_DONE;
+
+	switch (event) {
+	case NETDEV_REGISTER:
+		return virtnet_register_vf(event_dev);
+	case NETDEV_UNREGISTER:
+		return virtnet_unregister_vf(event_dev);
+	default:
+		return NOTIFY_DONE;
+	}
+}
+
+static struct notifier_block virtio_netdev_notifier = {
+	.notifier_call = virtio_netdev_event,
+};
+
  static __init int virtio_net_driver_init(void)
  {
  	int ret;

@@ -2877,6 +3177,8 @@ static __init int virtio_net_driver_init(void)
          ret = register_virtio_driver(&virtio_net_driver);
  	if (ret)
  		goto err_virtio;
+
+	register_netdevice_notifier(&virtio_netdev_notifier);
  	return 0;
  err_virtio:
  	cpuhp_remove_multi_state(CPUHP_VIRT_NET_DEAD);

@@ -2889,6 +3191,7 @@ module_init(virtio_net_driver_init);
  
  static __exit void virtio_net_driver_exit(void)
  {
+	unregister_netdevice_notifier(&virtio_netdev_notifier);
  	unregister_virtio_driver(&virtio_net_driver);
  	cpuhp_remove_multi_state(CPUHP_VIRT_NET_DEAD);
  	cpuhp_remove_multi_state(virtionet_online);

I have a question here: what if PT device driver module loads
and creates a device before virtio?

Initially i also had this question if we get NETDEV_REGISTER events for 
netdevs
that are already present. But it looks like 
register_netdevice_notifier() will cause
replay of all the registration and up events of existing devices.

/**
  * register_netdevice_notifier - register a network notifier block
  * @nb: notifier
  *
  * Register a notifier to be called when network device events occur.
  * The notifier passed is linked into the kernel structures and must
  * not be reused until it has been unregistered. A negative errno code
  * is returned on a failure.
  *
  * When registered all registration and up events are replayed
  * to the new notifier to allow device to have a race free
  * view of the network device list.
  */

Thanks
Sridhar
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