Does my graphics card ROM support EFI?

If you're wanting to try legacy-free OVMF-based GPU assignment, it might be a good idea to start by testing whether your graphics card has EFI support in the PCI option ROM.  I've written a small program to parse the ROM and report some basic info about the contents.  Here's example output:

$ ./rom-parser GT635.rom 
Valid ROM signature found @0h, PCIR offset 190h
 PCIR: type 0, vendor: 10de, device: 1280, class: 030000
 PCIR: revision 0, vendor revision: 1
Valid ROM signature found @f400h, PCIR offset 1ch
 PCIR: type 3, vendor: 10de, device: 1280, class: 030000
 PCIR: revision 3, vendor revision: 0
  EFI: Signature Valid
 Last image

This is what we typically expect to see, there are two headers, the first is type 0, which is a standard PC BIOS ROM, the second is type 3, an EFI ROM. If you don't have EFI support in the ROM, the OVMF solution will not work for you.  Newer graphics card will hopefully all have EFI support.

To get this program:

$ git clone https://github.com/awilliam/rom-parser
$ cd rom-parser
$ make

You'll need to copy the ROM to a file first, the program does not have support for enabling the ROM through pci-sysfs. To do this from the host:

# cd /sys/bus/pci/devices/0000:01:00.0/
# echo 1 > rom
# cat rom > /tmp/image.rom
# echo 0 > rom

If you get a zero-sized file, look for an error in dmesg. The ROM may only be readable initially after boot, before any drivers have bound to it. Use the pci-stub.ids= boot option to attempt to keep the device in a pristine, unused state.