[mrpippy]

Although if GVT-d gives the GPU fully over to the VM, which GPU will OS X itself be using? In the high-end 15" MBP, I suppose OS X could switch to the discrete GPU and let the VM use Iris Pro, but it's not a great solution and would only work on (the fairly small number of) dual-GPU Macs.

[veertu]

Actually gpu virtualization works quite similar to cpu. You don't pass a cpu core exclusively to a VM rather the cpu itself maintains independent contexts: for the host and each VM. When a CPU runs a VM it just switches the context. So is the GPU. You don't need two GPUs to make it work.

[jbssm]

I believe it doesn't have too, it can work in a way similar to optimus + prime on the Linux using the GPU.