Re: [RFC PATCH net-next v2 2/2] virtio_net: Extend virtio to use VF datapath when available

["Samudrala, Sridhar" <sridhar.samudrala@intel.com>]

On 1/26/2018 8:58 AM, Michael S. Tsirkin wrote:
> On Thu, Jan 11, 2018 at 09:58:39PM -0800, Sridhar Samudrala wrote:
> > @@ -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