Two GPUs - Monitors on 2nd GPU stay black but show mouse cursor

Bazzite
1

So I have 2 GPUs so I can drive 6 monitors.
I /was/ doing it previously with the onboard Intel card + hybrid/optimus. But I was running in to issues with OGL games. So I thought I’d throw a 2nd full GPU in and just use the nVidia drivers.

All 6 monitors show up in the display configuration, and I’m able to select their resolution, enable/disable them, move them around, etc.

But the 2 screens plugged in to the 2nd GPU just show a black screen. If I move the mouse over to them I can see the mouse.

If I change the order of the cards in /etc/environment then I can get the 2nd GPU working while the primary GPU stays dark other than the mouse.

/etc/environment 
KWIN_DRM_DEVICES=/dev/dri/card0:/dev/dri/card1

nvidia-smi shows both cards.

+-----------------------------------------------------------------------------------------+
| NVIDIA-SMI 565.57.01              Driver Version: 565.57.01      CUDA Version: 12.7     |
|-----------------------------------------+------------------------+----------------------+
| GPU  Name                 Persistence-M | Bus-Id          Disp.A | Volatile Uncorr. ECC |
| Fan  Temp   Perf          Pwr:Usage/Cap |           Memory-Usage | GPU-Util  Compute M. |
|                                         |                        |               MIG M. |
|=========================================+========================+======================|
|   0  NVIDIA GeForce RTX 3080 Ti     Off |   00000000:01:00.0  On |                  N/A |
| 53%   32C    P5             65W /  400W |    2157MiB /  12288MiB |     29%      Default |
|                                         |                        |                  N/A |
+-----------------------------------------+------------------------+----------------------+
|   1  NVIDIA GeForce RTX 4060 Ti     Off |   00000000:07:00.0  On |                  N/A |
|  0%   37C    P8              7W /  160W |      58MiB /   8188MiB |      5%      Default |
|                                         |                        |                  N/A |
+-----------------------------------------+------------------------+----------------------+

I’ve tried this before on other distros, and couldn’t get it to work, but then I saw this post:

And there’s a KDE dev in there saying it’s supported and should work… So I thought I’d ask here if anyone had any ideas.

I DID previously have optimus enabled on this install, so maybe that’s breaking multi-gpu stuff?

I also tried adding “nvidia_drm.modeset=1” to kernel options, but that didn’t change the behaviour.

Thanks in advance for any help!

2

I’ve tried this on a few other Distros, too, and get the same results.
Looks like I may just be trying to do something that Wayland isn’t’ capable of, sadly.

Seems to work OK in Xorg. But then I get to choose between shitty FPS in games or massive tearing issues everywhere. Grim.

3

I’ve now tried on Arch, Endeavor, Ubuntu 24.10, Kionite, Neon, Bazzite, PopOS Cosmic, and Manjaro.
I’ve tried with NV 555, 560, and 565.

It’s always the same. Works fine in X, but Wayland is unable to display anything on the 2nd GPU, other than the mouse cursor.

Cosmic got the closest to working - wallpaper was visible, and I could see the window outlines if I dragged them to GPU2, but as soon as I drop them on the desktop the screen goes black - even the wallpaper goes away.

This is either a bug in the NV drivers, or a missing feature in Wayland. Either way, just have to stick with X for now.

Should probably submit a bugzilla, but I’m not even sure what to put the bug against - is this a NV issue? A wayland issue? A Vulkan issue?

It’s certainly NOT a KDE issue - it’s something deeper in the guts.

4

Ok, so this seems to be a confirmed bug with nVidia EGL and the fix should be in the next driver release.

Details here: Using two NVIDIA GPUs monitor ok in the first gpu, one is always black on second gpu. ( Although shows the mouse cursor ok) - #19 by gilvbp - Linux - NVIDIA Developer Forums