Thank you very much, it solved my issue too. I got same "vfio-pci BAR 0: can't reserve memory" issue just after pve 7.2-3 upgrade. Also i needed to addSolved!
echo 1 > /sys/bus/pci/devices/0000\:09\:00.0/remove
echo 1 > /sys/bus/pci/rescan
"video=efifb:off"to kernel boot options, so i even could passthrough primary GPU in x16 slot.