PRIME offloading with two dedicated Nvidia GPUs?

Ask Fedora
1

Hello, i have been trying to get prime offloading working on my system unsuccessfully for a few days now. I own both a GTX 1070 and a RTX 3080, they are both installed in the system and when i run nvidia-smi they both show up fine. I am on Fedora 42 with a X11 based DE

My main monitor is a CRT and requires an interlaced output to get a high refresh rate, something the 30 series cards is not capable of. My plan was to have the 1070 run everything, and then prime offload my games to the 3080. I had this working very briefly but it suddenly stopped working and I can’t for the life of me find out why.

Xrandr only lists a single provider, that being whichever one is running X. When i try to prime offload to the 3080 from the 1070 or vice versa it just boots the program on whichever GPU has the monitors plugged in. I’ve tried tons of different xorg.conf setups and reinstalling nvidia drivers, but almost all the documentation i can find is only about a iGpu + dGpu setup, i’ve tried everything I could find on the internet about it.

I would think it’s simply not possible but I had it working a few days ago.

2

I have both cards showing as providers again by reinstalling my nvidia drivers generating a new xorg config through nvidia-settings,

Providers: number : 2
Provider 0: id: 0x1b7 cap: 0x1, Source Output crtcs: 4 outputs: 7 associated providers: 1 name:NVIDIA-0
Provider 1: id: 0x3b4 cap: 0x2, Sink Output crtcs: 4 outputs: 8 associated providers: 1 name:NVIDIA-G0

and if i run glxgears or a native game with __NV_PRIME_RENDER_OFFLOAD=1 __GLX_VENDOR_LIBRARY_NAME=nvidia then it shows it’s properly offloading through nvidia-smi, but I cannot get anything to offload under proton at all.

Still trying to figure this out

3

I have vkcube working as well by running

__NV_PRIME_RENDER_OFFLOAD=1 __VK_LAYER_NV_optimus=NVIDIA_only vkcube --gpu_number 1

From what I can gather It seems the issue is that when trying to load something through proton, it’s always using the GPU that xorg is running on. Perhaps this is a rather a proton issue.