Unfortunately I started having a similar problem again…
I can’t update Radeon Software. Every time I try to do it, either through the current version of AMD Radeon Software or by downloading a new installer. Each time the driver installer just crashes and causes hard reboot of my VM.
Of course the reason I need newer drivers is Battlefield 2042. 
I didn’t change anything in the VM XML and each time I updated BIOS (on Asus ROG Strix X570-F), I was using the default config + mentioned above changes in config (IOMMU enabled, SVM enabled, CMS disabled, SR-IOV disabled). Does anyone have any idea what’s different about the newest AMD drivers?
To be precise, the versions I tried to install are:
Both had the same effect - crash and hard reboot when starting the installer.
Nevermind, I fixed that with changing the following BIOS settings:
Advanced → AMD CBS → NBIO Common Options → ACS Enable
Advanced → AMD CBS → NBIO Common Options → PCIe ARI Support
Advanced → AMD CBS → NBIO Common Options → PCIe ARI Enumeration
I searched them… by searching “vfio bios” on this forum, lol. But I’ve never seen those options in my BIOS before, so they must’ve come to ASUS ROG Strix motherboards with some recent BIOS update… or maybe I was blind and lucky to have VFIO working without these options, heh.
Did you enabled them or disabled them? On my bios they are on auto
You need ACS Enable set to enabled. What this does it creates proper separated IOMMU groups. In the same way as the, so called, ACS override patch does for mainboards that do not have this feature. The other two options listed in the post above should not be needed for PCIe passthrough as far as I understand them. I have them enabled on one of my computers as well, but not for PCIe passthough, but to use an SR-IOV capable device. On the other hand the software we call UEFI has shown to have terrible software quality in many cases. So if you have problems with passthrough you could try to toggle them regardless.
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