Can I passthrough an NVIDIA GPU if its the only GPU installed?

[Servs]

I am currently working on passingthrough a GT 730 and having trouble getting unRaid to stop using it.

I have previously passed through this gpu without any vbios or issues, but that was with x2 GPU installed.

I know it is possible to stop unraid from binding the GPU on boot but it doesnt seem to be working. What am I doing wrong?

 

syslinux config:

 

kernel /bzimage
append vfio-pci.ids=10de:1287,10de:0e0f pcie_override=downstream,multifunction initrd=/bzroot

 

 

[Squid]

You should be doing the isolation via Tools - System Devices.

[Servs]

3 minutes ago, Squid said:

You should be doing the isolation via Tools - System Devices.

The only option i see there is to select both the vga and audio and "Bind Selected to VFIO at Boot". Would that not force unRaid to use it on boot?

[Squid]

No that isolates it from the system.  (And dont forget to also remove your manual edits to syslinux.cfg)

[Servs]

6 minutes ago, Squid said:

No that isolates it from the system.  (And dont forget to also remove your manual edits to syslinux.cfg)

Okay, it appears if though unraid believes its binding it, but then doesnt bind it...

[Squid]

Why do you think it's not binding it.

 

[Servs]

1 hour ago, Squid said:

Why do you think it's not binding it.

 

well its still using it at boot to display unraid terminal and wont let me use it for VM so im confused.

[ghost82]

12 hours ago, Servs said:

its still using it at boot to display unraid terminal

This is ok, you will get some video output on boot, because vfio driver attaches after some other things.

You should have last lines on the monitor outputting something like:

vfio-pci 0000:xx:xx.0: vgaarb: changed VGA decodes: olddecodes=io+mem,decodes=io+mem:owns=io+mem

where vfio takes control over the gpu.

 

12 hours ago, Servs said:

and wont let me use it for VM

This depends on something else.

[tjb_altf4]

Pretty sure vfio binding happens too late to work for the primary display device.

Passing a correct vBIOS should allow the card to be passed to the VM successfully in this scenario.

[Servs]

On 7/8/2022 at 3:47 AM, tjb_altf4 said:

Pretty sure vfio binding happens too late to work for the primary display device.

Passing a correct vBIOS should allow the card to be passed to the VM successfully in this scenario.

I believe you are right, as the monitor displays the unRaid command line interface indefinitely regardless of the vfio stating its taken over or not. Sadly passing the vBIOS doesnt work either, so im wondering if maybe this is just an NVIDIA thing? I know in the past that NVIDIA gpu were hit or miss with passthrough if they were the only card present, i just figured that would have been fixed by now. Idk where to go from here really except buying a 2nd gpu sadly

[Servs]

Update:

Im not really sure if my vbios was corrupted or something, but after generating a new one, and passing it through, the VM took control of the GPU. So thnak you for the help!

[ghost82]

On 7/8/2022 at 10:47 AM, tjb_altf4 said:

Pretty sure vfio binding happens too late to work for the primary display device.

Passing a correct vBIOS should allow the card to be passed to the VM successfully in this scenario.

Yes and no

the "issue" here is that the primary gpu is flagged as boot vga and when this happens the bios makes a copy of the gpu rom (however this happens or doesn't happen depending on the bios too!), and this copy can be freely modified in the memory; however if this happens, when it comes to vfio, you could have invalid pci rom errors because you are reading the shadow copy of the rom image that is no more a 1:1 copy.

That's why passing a copy of the raw vbios fixes the issue.

I would say it's not because vfio happens too late but because of the native way it works for the primary gpu (at the bios level).

Edited July 19, 2022 by ghost82