Specifically, using network I/O as an example, I should directly assign the NIC to one guest VM (using pci-assign option),  after that all other guest VMs should perform network I/O through that VM rather than the host OS.

Is there currently any viable approach to do this? 

If not, I want to implement one. Currently I'm thinking of combining nahanni shared memory and vhost architecture to implement it, is there any other suggestions?

Thanks for any help.