Sounds suspiciously like this hardware quirk[0] that was only supposed to affect Hawaii/Bonaire... Guess it's a little more widespread. Easily fixed, I guess[1].

Then again Nvidia cards have their own set of horrible problems too, although theirs are somewhat on the side of malicious intent rather than incompetence.

[0] - https://github.com/qemu/qemu/blob/master/hw/vfio/pci-quirks....

[1] - https://github.com/qemu/qemu/blob/master/hw/vfio/pci-quirks....