[libvirt] [PATCH 0/6] RFC: qemu: virtio-{non-}transitional support
Daniel P. Berrangé
berrange at redhat.com
Tue Jan 15 17:06:04 UTC 2019
On Sun, Jan 13, 2019 at 06:12:02PM -0500, Cole Robinson wrote:
> This series adds the beginnings of support for virtio-transitional
> and virtio-non-transitional qemu devices.
>
> qemu patches, queued for qemu 4.0.0:
> https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg00923.html
> Previous libvirt discussion around this:
> https://www.redhat.com/archives/libvir-list/2018-August/msg01073.html
>
> Long story short we need to expose these options so apps have a
> usable way to support rhel6 + virtio + q35.
>
> This series only covers exposing the associated device models
> for disk and rng devices to make sure I'm on the right track.
> serial, net, scsi, input-host, balloon 9p, vsock, vhost-scsi
> still need to be implemented. Those should follow the rng
> example, except vhost-scsi may need to be a different approach.
virDomainNetDef is a mess because it *still* doesn't use a enum
for the device model :-( We really must fix that rather than
blindly allowing arbitrary passthrough of hypervisor specific
names.
I recall Laine had patches for this some 4/5 years ago, but
can't remember why we never merged them.
> The main RFC bits here are:
>
> * The disk approach. danpb and I briefly discussed on IRC adding
> new bus= values vs a new model= attribute. We decided model=
> is the lesser of two evils, since bus= handling in apps is
> tied with target= generation, so adding new virtio-X bus=
> values will cause more work for apps. These patches add
> a <disk model=X/> attribute
Yes, using 'bus' will have a very painful ripple effect on
mgmt apps we should avoid at all costs.
> * The XML and naming. Previous discussions seemed to favor adding
> new model-style values rather than a 'transitional' attribute
> or similar. So these patches add model='virtio-transitional'
> and model='virtio-non-transitional'
Yep.
> * The PCI address handling. I just mapped virtio-non-transitional
> to imply plain PCI addressing. I think that's all we need but
> I'm not positive so I'd appreciate a review of that approach.
This was inverted, as Andrea already clarified
Regards,
Daniel
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