Not necessarily. I managed to get it working with a single GPU, by unbinding it from the host and binding it to the VM. Unfortunately it does mean that you have to stop X11 and all programs, and going back doesn't work (the GPU freezes the machine when the proprietary NVIDIA driver loads), but it's still better than dual-booting because background services continue to run. It certainly is easier with separate GPUs, though.
You can always have multiple VM's with gpu passthrough, so it's almost like dual boot kind of setup, but you can still run other things on the host. It works pretty well for me, only downside being that you're limited to single VM running at the time.
