[virtio-dev] Re: [Qemu-devel] [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net

Michael S. Tsirkin
Thu, 21 Jun 2018 18:20:13 -0000

On Thu, Jun 21, 2018 at 04:59:13PM +0200, Cornelia Huck
wrote:
> On Wed, 20 Jun 2018 22:48:58 +0300
> "Michael S. Tsirkin" <mst at 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.

True. I'm a bit unhappy that it's virtio net specific though
since down the road I expect we'll have a very similar feature
for scsi (and maybe others).

But we do not have a way to have fields that are portable
both across devices and transports, and I think it would
be a useful addition. How would this work though? Any idea?

--
MST