GPU Passthrough

tjkreidl

@gb.123 Interesting -- alert the XCP-ng team to take a closer look, if they haven't seen this already.

forbiddenera

@gb.123 what xen and gurst version etc were you using?

I'm about to try GPU PT and having USB st the same time is important

Vagrantin

Hello

Hope this help here is how I manage to configure GPU Passthrough.

In my case I have follow the documentation on XCP-ng website : https://docs.xcp-ng.org/compute/

To sum up with XOA 8.3 here is what I did:

ssh to XCP host, to identify the GPU PCI and run lspci to find my GPU.

[root@xen ~]# lspci
...
0f:00.0 VGA compatible controller: NVIDIA Corporation GA102 [GeForce RTX 3090] (rev a1)

Then disable the GPU for being used by XCP-ng itself( Dom0) using the XCP-ng uuid

[root@xen ~]# xe pci-list
uuid ( RO)           : 7970825f-dd1c-c270-93a3-6761f00e1362
    vendor-name ( RO): NVIDIA Corporation
    device-name ( RO): GA102 [GeForce RTX 3090]
         pci-id ( RO): 0000:0f:00.0

xe pci-disable-dom0-access uuid=<pci uuid>

3 reboot the XCP-ng host

4 Then from XOA attached the PCI related to my GPU to my guest VM.

5 install official Nvidia drivers ( closed source ) and have then the card available in the guest.

What I didn't do is adding a vGPU in the guest configuration:

I did it some times ago, also I don't recall having to do any specific configuration in the Bios to make this work.

PS: I have an issue, I don't have output to the Display port or HDMI of this video card, which is not a blocker for me as that's not my immediate needs.

Best.

gskger

I am running NVIDIA P40s on a DELL R720/R730 and a NVIDIA A2000 12GB on a DELL Optiplex 9010 in my playlab. Getting the GPUs to be accessible for VMs was quite easy: shutdown the XCP-ng host, install the GPUs, start the host again, activate the GPU in the advanced settings of the host in the PCI Devices section (“Passthrough enabled”). The host will restart at this point after displaying a warning. That's it – the GPU can now be assigned to a VM in the VMs advanced settings. I do use the GPUs for AI workloads under Debian though, so your use case might vary.

coolsport00

@gskger that's interesting you are using a NVIDIA GPU. The documentation states, "due to proprietary reasons, currently NVIDIA is not supported".. But that's for vGPU, not just general passthrough. I assume you're using it for straight passthrough to a VM and not to multiple VMs?

I wish this worked for multiple VMs. I'd like to move to XCP from VMW. But, I have till next Summer to decide....

gskger

@coolsport00 Yes, I am using the GPUs with llama-swap to serve qwen3.8-27b and qwen3.6-35b for local inference with Bifrost as an AI gateway for local and cloud AI provider. Never tried vGPU myself.

coolsport00

@gskger Understood.. Thanks for clarifying @gskger

tjkreidl

@coolsport00 See if any of this helps:

Here is the step-by-step guide to configure the NVIDIA GeForce RTX 3090 for full PCI passthrough to a virtual machine in XCP-ng.Step 1: Identify the GPU on the XCP-ng HostFirst, log in to your XCP-ng host via SSH or use the local console shell to find the exact hardware address of your RTX 3090.Run the following command to list your PCI devices and filter for NVIDIA:bashlspci | grep -i nvidia
Use code with caution.Look for the lines corresponding to your RTX 3090 and its Audio Controller. They will look similar to this:text01:00.0 VGA compatible controller: NVIDIA Corporation GA102 [GeForce RTX 3090] (rev a1)
01:00.1 Audio device: NVIDIA Corporation GA102 High Definition Audio Controller (rev a1)
Use code with caution.Take note of the PCI identifiers (e.g., 01:00.0 and 01:00.1). Note that your specific identifier numbers might vary based on your motherboard layout.Step 2: Hide the GPU from the Control Domain (Dom0)To prevent the main XCP-ng host system (Dom0) from seizing control of the graphics card, you must tell it to ignore those PCI IDs on boot.Instruct XCP-ng to assign the GPU components to the passthrough driver (xen-pciback) by executing this command (replace 01:00.0 and 01:00.1 with your actual IDs found in Step 1):bash/opt/xensource/libexec/xen-cmdline --set-dom0 "xen-pciback.hide=(01:00.0)(01:00.1)"
Use code with caution.Reboot the physical server for this driver isolation configuration to take effect:bashreboot
Use code with caution.Step 3: Verify the IsolationOnce your host boots back up, check that the hardware isolation worked as intended.Run this command to verify that the xen-pciback driver has correctly claimed the card:bashxl pci-assignable-list
Use code with caution.You should see your GPU addresses printed in the terminal, confirming they are ready to be passed into a virtual environment:text0000:01:00.0
0000:01:00.1
Use code with caution.Step 4: Attach the GPU to your VM
You can attach the isolated card either visually using Xen Orchestra (XO) or straight from the command line interface.Option A: Using Xen Orchestra (Recommended)Navigate to the Xen Orchestra management interface.Go to the VMs tab and click on the target virtual machine (ensure it is powered down).Click on the Advanced tab of that VM.Scroll down to the PCI devices block.Select both the RTX 3090 graphics and audio IDs from the dropdown checklist and save your changes.Option B: Using the Command Line (CLI)Find the unique identifier (UUID) of your VM:bashxe vm-list name-label="Your_VM_Name"
Use code with caution.Assign the GPU to that VM UUID using the following command syntax:bashxe vm-param-set uuid=<VM_UUID> other-config:pci=0/0000:01:00.0,0/0000:01:00.1
Use code with caution.Step 5: Boot and Install DriversPower on your virtual machine. You can now download and install the official desktop NVIDIA GeForce Drivers directly inside the guest operating system. The installer will recognize the device normally, and you do not need to register a license server or install vGPU client software.

coolsport00

Hi @tjkreidl . Thank you for your detailed response, but I don't need/use standard GPU passthrough to 1 VM, but to 15. So I need vGPU capability. From the XCP documentation, it looks like for now, it's not possible/supported due to proprietary issues in the Xen OS, at least with NVIDIA cards, which is what I currently use. I guess I could switch to some other vendor, but would like to stay with what I know. Appreciate it!

tjkreidl

@coolsport00 Why not then just do the GPU passthrough for the entire host and just put the VMs on that host that you want to leverage the GPU? To get specific vGPU capabilities, my recollection is that you'd need to use a GPU that most likely requires licensing, at least as far as NVIDIA is concerned.

coolsport00

@tjkreidl
hmm...generally, the 15 VMs would take up much more resources than just one Host would be able to disperse. Let me explain...

Currently, with VMW, I have just 5 VMs per ESXi Host, and have 3 physical Hosts, 2 NVIDIA Tesla T4 (a bit legacy now) cards in each Host. I virtually passthrough the underlying cards in each Host to each of the 5 VMs. Not entirely sure how VMW does it architecturally, but VMW disperses the load between the cards amongst the 5 VMs. And maybe that's done in conjunction with the NVIDIA driver installed on ESXi. ‍️Also, the reason I only have 5 VMs per Hosts is because I use them for students to RDP into to run high graphics-need engineering applications (AutoCAD, Revit, inventor Pro). I use Microsoft RDS (really an underrated VDI solution imo) and it "round-robins" the student RDP connections amongh the 15 VMs. I can have up to around 10 RDP connections to each VM. But, according to specs, theoretically I can have around 20 RDP connections. So, as you can see...resources can get tight really quick..thus, only 5 VMs per Host. Anyway, that's what I'm wanting to achieve with XCP. I have a little time...till next summer...to make a decision on what h/v to migrate our VMW VMs off of. My hope is that XCP will be the choice. Ultimately, I'm the one to make the choice, but this would be a definite negative. PVE is my only other option. Not sure they have vGPU passthrough tho either (I have yet to research it).

Thanks for all the info and assist!