Same problem here with RX 470. The happens both on rmmod'ing amdgpu or
attempting to unbind, even when using the drm-next-4.9-wip branch.

It would be great if this worked to be able to switch to GPU passthrough
without a reboot. The windows driver seems to be already behaving well, I can
start/shutdown the vm multiple times and then hand over the card to amdgpu
without problems, only taking it away from amdgpu locks up the machine.