Just have experienced the same issue with 6.12.0 hanging on reboot. Thus found current tread. Pulled the flash drive in search of vfio-pci.cfg and didn't found such (don't use VM's so maybe because of that). So I've put the flashdrive back and the 6.12.0 booted up as usual. I presume there is something else, other than vfio-pci.cfg file that causing the issue.