Hmm, I'd suggest to move the whole thing into the virtio-gpu section.
There is no such thing as a "resource" in general virtio context ...
If this is moved into the virtio-gpu section, then any device type that imports resources will have to refer to something defined by the GPU device type. This would make the GPU device type a sort of special device type that isn't just a leaf node of the spec. I think it's better to define 'resource' as a top level concept for virtio devices, even if the specifics of what a 'resource' is are defined by individual device types.
-David