Comment 3 for bug 1835400

Based on a chat with Dan Berrangé (thank you), there are two problems
here:

(1) Nova's validation of network models is incomplete, i.e. the method
    is_vif_model_valid_for_virt() has an incomplete list of hardware
    models

(2) The "model names returned by libosinfo are *NOT* required to be
    valid libvirt network model names". I.e. there is no such
    "virtio-1.0-net" model name in libvirt, if we see here:
    https://libvirt.org/git/?p=libvirt.git;a=blob;f=src/conf/domain_conf.c#l515

And libosinfo is just telling us that the guest supports
'virio-1.0-net'. There are two ways to provide that: the
"virtio-transitional" vs. "virtio-non-transitional" devices.

Where "virtio-transitional" provides a device that will auto-negotiate
virtio 1.0 support; while "virtio-non-transitional" provoides a device
that is fixed to always use virtio 1.0 support.

    - - -

The recomendation for all CentOS 7.0 devices is to go with 'virtio'.

    - - -

Documentation on "virtio-transitional" vs. "virtio-non-transitional":

    https://libvirt.org/formatdomain.html#elementsVirtioTransitional)