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Date: Thu, 21 Jun 2018 16:59:13 +0200
From: Cornelia Huck <cohuck@redhat.com>
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Subject: Re: [Qemu-devel] [virtio-dev] Re: [PATCH] qemu: Introduce
 VIRTIO_NET_F_STANDBY feature bit to virtio_net
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Siwei Liu <loseweigh@gmail.com>, "Samudrala, Sridhar" <sridhar.samudrala@intel.com>, Alexander Duyck <alexander.h.duyck@intel.com>, virtio-dev@lists.oasis-open.org, aaron.f.brown@intel.com, Jiri Pirko <jiri@resnulli.us>, Jakub Kicinski <kubakici@wp.pl>, Netdev <netdev@vger.kernel.org>, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com, Joao Martins <joao.m.martins@oracle.com>, Venu Busireddy <venu.busireddy@oracle.com>, vijay.balakrishna@oracle.com

On Wed, 20 Jun 2018 22:48:58 +0300
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Wed, Jun 20, 2018 at 06:06:19PM +0200, Cornelia Huck wrote:
> > In any case, I'm not sure anymore why we'd want the extra uuid.  
> 
> It's mostly so we can have e.g. multiple devices with same MAC
> (which some people seem to want in order to then use
> then with different containers).
> 
> But it is also handy for when you assign a PF, since then you
> can't set the MAC.
> 

OK, so what about the following:

- introduce a new feature bit, VIRTIO_NET_F_STANDBY_UUID that indicates
  that we have a new uuid field in the virtio-net config space
- in QEMU, add a property for virtio-net that allows to specify a uuid,
  offer VIRTIO_NET_F_STANDBY_UUID if set
- when configuring, set the property to the group UUID of the vfio-pci
  device
- in the guest, use the uuid from the virtio-net device's config space
  if applicable; else, fall back to matching by MAC as done today

That should work for all virtio transports.