Re: [libvirt] [PATCH 0/6] RFC: qemu: virtio-{non-}transitional support

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.

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

* 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'

* 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.