Re: [virtio-dev] [RFC PATCH net-next v2 1/2] virtio_net: Introduce VIRTIO_NET_F_BACKUP feature bit

On Tue, 23 Jan 2018 03:23:57 +0200, Michael S. Tsirkin wrote:

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b. next-gen silicon may be able to disguise as virtio device, and the
   loop check in virtio driver will prevent the legitimate bond it such
   case.  AFAIU that's one of the goals of next-gen virtio spec as well.    

In fact we have a virtio feature bit for the fallback.
So this part does not depend on how software in guest works
and does not need software solutions.  

You mean in the new spec?  Nice.  Still I think people will try to
implement the old one too given sufficiently capable HW.  

Existing HW won't have the BACKUP feature so the new functionality
won't be activated. So no problem I think.

I meant code that compares of netdev_ops, e.g.:

+	/* Skip our own events */
+	if (event_dev->netdev_ops == &virtnet_netdev)
+		return NOTIFY_DONE;

Would be an obstacle to bonding virtio_nets.  But that's just one of
the thoughts, perhaps of disputable value.  Anyway, separate netdev and
netdev_ops will solve this, and I think we agree that's preferable :)