https://bugs.freedesktop.org/show_bug.cgi?id=100399
--- Comment #6 from jimijames.bove@gmail.com --- (In reply to Michel Dänzer from comment #5)
(In reply to jimijames.bove from comment #4)
Before I switched to AMD, I was passing an NVidia GPU (GTX 660) into my virtual machine, and I could unbind and rebind it between nouveau and vfio-pci as much as I wanted. No trouble at all. Even while X was running, once DRI3 support came.
You can still do that with DRI3, you just have to prevent Xorg from using the secondary GPU, e.g. via
Section "ServerFlags" Option "AutoAddGPU" "off" EndSection
in /etc/X11/xorg.conf.
Well, sort of. That option is what allows me to bind the card to amdgpu without X crashing (even though I've been told in the past that I shouldn't need that option for that functionality), but this bug--not being able to UNbind it from amdgpu--does not go away with that option.