Nvidia Quadro P400 not working on Ubuntu server via GPU/PCIe passthrough

olivierlambert

That answer is incorrect. Passing an entire PCIe device shouldn't make a diff.

Maybe it's a problem on the IOMMU side, I don't know. It will be easier to work on it with an actual card.

TheFrisianClause

@olivierlambert In that case, lets hope you can resolve it once the P400 is delivered. Curious what you find and how there is a way to resolve the issue...

olivierlambert

I have no idea and not great hope due to our other priorities but we'll see.

TheFrisianClause

@olivierlambert I think the conclusion we can make is that I need to hide the Hypervisor from the Nvidia driver which is also mentioned here: https://www.reddit.com/r/XenServer/comments/r12p0q/pci_passthrough_quadro_p400_to_ubuntucentos_vm/

So it is an Error 43, as I think this is plausible as for Proxmox I do this as well by adding this into the vm .conf file

cpu: host,hidden=1,flags=+pcid

Which hides the hypervisor from the VM in KVM perspective.
Is there an equivalent for XCP-NG?

olivierlambert

No equivalent in Xen yet
Nvidia changed its policty recently to avoid blocking virt in their drivers. So the problem should not be here.

TheFrisianClause

@olivierlambert Could it be something with the 'VFIO' modules maybe in KVM? I honestly have no clue anymore... So I think my best guess is to wait your research on this out...

olivierlambert

I just got the card, but my agenda is very very busy ATM. I'll try to do the PCI passthrough on my spare time (which is not very often either)

TheFrisianClause

@olivierlambert No problem take your time, I will check in regularly to see if there has been an update or some sorts...

olivierlambert

Okay so doing some tests now, I can reproduce the issue. So the questions are:

Did it work before? (older versions of XCP-ng?) -> removing regressions from the equation
Is P400 limited for PCI passthough by NV driver? It's still not clear. If it's the problem, this require a code change in upstream Xen to be able to hide it.

TheFrisianClause

@olivierlambert

I have no idea if it worked on the earlier versions of XCP-NG, I don't think so as I have I believe tested this on XCP-NG 8.0 and 8.1 if I remember correctly. (Also created forum posts about this in 2019/2020).

I dont think it is limited for PCI passthrough as I am using an NVidia driver on the VM within proxmox without any issues.

I am pasting a screenshot of the Nvidia driver I am currently using on the VM inside proxmox:

olivierlambert

That might be because Proxmox is hiding the hypervisor underneath. Hard to tell because of this fracking drivers

TheFrisianClause

@olivierlambert
Hmm yeah its quite a hassle with these drivers for some reason.... If you need some extra information which could help let me know... I can send some other details which are now on the proxmox host and the Ubuntu VM?

How about the VFIO modules which I also mentioned earlier? Is this something that has to be added to XCP-NG maybe? As I also have a topic on Reddit and this person has the same problem but then with an T400.
https://www.reddit.com/r/XenServer/comments/r12p0q/pci_passthrough_quadro_p400_to_ubuntucentos_vm/hrlaqxl/?context=3

olivierlambert

If it's hypervisor detection, the "only" thing needed is a Xen modification, but this is not trivial (if it's really that). I can assume it's the case.

In the meantime, can you double check if XCP-ng 7.6 is affected too? (last hope to check if it's not a regression).

TheFrisianClause

@olivierlambert Can try that on my spare server, will try and see if I can do it today. I will update this once I am finished.

TheFrisianClause

Currently I have no time to test this as the machine itself is also heavily used by other users.... But I believe the 7.6 version has this issue as well, as I remember testing this on version 7.x.

TheFrisianClause

Alright tested it with 7.6
Seems to not work as well...

[  165.594038] [drm] [nvidia-drm] [GPU ID 0x00000006] Loading driver
[  165.594040] [drm] Initialized nvidia-drm 0.0.0 20160202 for 0000:00:06.0 on minor 1
[  171.958377] NVRM: GPU 0000:00:06.0: RmInitAdapter failed! (0x22:0x56:667)
[  171.958424] NVRM: GPU 0000:00:06.0: rm_init_adapter failed, device minor number 0
[  171.963805] NVRM: GPU 0000:00:06.0: RmInitAdapter failed! (0x22:0x56:667)
[  171.963848] NVRM: GPU 0000:00:06.0: rm_init_adapter failed, device minor number 0

Same error....

olivierlambert

Okay so at least "it's good news": it's not a regression So I assume it's required to hide the hypervisor underneath.

TheFrisianClause

@olivierlambert Yes I believe so, do you need more information on this?

olivierlambert

Not yet, I need to talk with Xen devs when I can on how to achieve that.

TheFrisianClause

@olivierlambert Alright, thanks for the effort