[vfio-users] Failed to mmap 0000:01:00.0 BAR 3. Performance may be slow

[Konrad Eisele]

I try to passthrough the primary graphic card (GForce 710b
at slot 0000:01:0.0) to a win kvm guest. The host runs
headless. I have blacklisted the nvidia drivers and bound
the drivers to vfio-pci on startup. However when starting qemu
I currently get the error:

(qemu) qemu-system-x86_64: -device vfio-pci,host=01:00.0,multifunction=on:
Failed to mmap 0000:01:00.0 BAR 3. Performance
may be slow

It seems that efifb is jumping in and allocating some region:

$cat /proc/iomem
...
0000000-00000000 : PCI Bus 0000:00
 00000000-00000000 : PCI Bus 0000:01
   00000000-00000000 : 0000:01:00.0
     00000000-00000000 : vfio-pci
   00000000-00000000 : 0000:01:00.0
     00000000-00000000 : efifb
 00000000-00000000 : PCI Bus 0000:03
   00000000-00000000 : 0000:03:00.0
...

So I added efifb:off to grub's kernel cmdline

cat /proc/cmdline:
.... video=vesafb:off,efifb:off

However that doesnt seem to help. Does anybody know howto
prevent the above error?
What more do I have to do to passthrough the primary graphics card to a
guest
running on a headless server? Any tips?
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