I have been working on porting virtio devices too. Actually for now only networking driver complete The main difference between Stefen's version is virtio devices attaches directly to pci bus.
I don't think this is a good idea. There are other transports for virtio than pci, e.g. virtio-mmio. And virtio-mmio behaves differently enough from virtio-pci that supporting both in all virtio device drivers would be a PITA.
But I think your name of vio for the network devices is better than NetBSD's vioif. I think I will rename it, too.
