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Nvidia GPU not used as primary display driver on passthrough mode

Stephen Garcia


Hi all,

Running into a problem setting this up and I dont know where to look next.



Server: Cisco C240M5

GPU: Nvidia Tesla T4

Nvidia Driver: 451.82-tesla-desktop-win10-64bit-international

Hypervisor version 8.2 (thried with 8.1 just in case, same thing)

VDA version: 2006


As a PoC this is what I've done

  • spooled up a vanilla Windows 10 VM
  • ran windows updates
  • installed Nvidia driver
  • installed xen tools
  • installed VDA


At this point when when runing the VM it indicates that it is using microsoft display driver. Important to note that the T4 is currently visible to the VM as a device and the driver installed succesfully, confirming that the card is present considering that it does a compatibility check. MSIAfterburner sees the card but its graphs stay bottomed out no matter what GPU intensive application is running (or trying to run as well as they can using the basic driver anyhow). 


Just in case I used the command to enable Nvidia:

NVFBCEnable.exe -enable -noreset


This had no effect


Proceeded to follow a write up that indicated the use of registry keys to influence the driver desision. 

Path: HKLM\Software\Citrix\Graphics
Key: AdapterMerits

DWORD: Nvidia, CitrixDoD, CitrixIDD (with the Nvidia DWORD having the highest value)


This had no effect either.


At this point I dont know what else to try. If im not mistaken there shouldnt be any need to install drivers on the hypervisor itself as this is on passthrough mode and not vGPU. Any secrets to get GPU passthrough to work?




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5 answers to this question

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Do you have the licensing from NVIDIA installed on a license server and the service registered with your VM(s)?  Are the drivers properly installed on your host? What do you get if you run nvidia-smi from the CLI on your XenServer/Citrix Hypervisor host? You won't be able to run it without properly installed and configured licensing.



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Yes, things are way more restrictive now and you need licensing of ne form or another, plus a whole separate NVIDIA license server. There are pretty good docs on teh NVIDIA Web site that spell this out, plus some blog posts. Good luck getting it all together! Remember that you need bot a server license as well as client licenses.



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The NVIDIA GPU always has to be designated a secondary display unit; you need some sort of video card as your primary in order to operate a Citrix Hypervisor or XenServer console.

What do you have installed as far as whatever video board came with the server before you installed the T4 and drivers?



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Hi Tobias. Im not sure I follow. The server itself is runing with its integrated gpu with no issues. I can access its console. The problem is with the guest VM having avalable but not using the T4 assigned to it as GPU passthrough.


The Citrix Hypervisor has had no gpu drivers installed on it. I remember a few years back when using GRID vGPUs there was a need to install nvidia drivers on xenserver but I havent found documentation when the usage is GPU Passthrough. Is the assumption that GPU passthrough does not require drivers on the host hypervisor for it to work on the guest VM correct?

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Licensing was the issue. A misunderstanding coming from years ago having had a Xendesktop environment before Nvidia's subscription model came into effect plus not being clear on GPU passthrough compute vs graphics usage.


From our nvidia rep:


For remote visualization environments the vGPU driver is required even in Pass-through mode and as such it requires a license. The only difference is that you only need to install the vGPU guest driver on the VM but you don't need to install anything on the hypervisor host


So you should remove the public Tesla driver for Windows that you installed on the VM as that one can only be used for compute and not graphics. And install the vGPU driver instead.


Thanks for pointing us in the right direction.

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