5.3.3. (Optional) Enable Large Prefetchable BAR Support
If you hit BAR allocation failures in dmesg or VFs fail to enable, add the following:
pci=hpmmioprefsize=1G,realloc
Notes:
Tune 1G upward if multiple adapters require large prefetchable BAR space.
This is a platform/MMIO sizing issue, not a libvirt issue.