Ancalagon

I was finally able to fix this macOS VM. I'm not sure exactly what combination of things it was that fixed it (some things I eventually undid before it worked). I had to boot into a new macOS VM installation rescue environment and scan the broken VM's disk for errors, which it found and fixed. That may have been the main problem, but it wasn't the only thing required because it still wasn't working afterwards.

I got this working! First, I was able to successfully pass through the GPU after switching to legacy CSM boot. I was then able to save my vbios rom. Then after adding the vbios rom to the VM XML and switching back to EFI boot, the GPU passthrough works! I can also confirm the GPU is properly reset when rebooting the VM as well.