Here's a thought, could we improve network performance by creating a paravirtual network device which doesn't emulate ethernet? It shouldn't be too hard to just whack IP packets pretty much directly over a virtio link.
This should improve performance when using a "user" host connection and we could introduce a tun host connection instead of tap for this setup.
Does anyone have any thoughts on how worthwhile this would be? Would the performance improvement justify the effort involved?