[SOLVED] Dual GPU passthrough only working on one card

[niklas_t]

Hey,
So i just setup a Proxmox 7.2 server on my workstation with these specs:
Intel 6850k
2x GTX 1080
32gb ram

I followed this guide: https://www.youtube.com/watch?v=12JtV1ou6EQ&ab_channel=CraftComputing
which references this guide: https://www.reddit.com/r/homelab/comments/b5xpua/the_ultimate_beginners_guide_to_gpu_passthrough/ (where i did everything except for the unsafe interrupts part)
and got some additional information from this: https://manjaro.site/tips-to-create-ubuntu-20-04-vm-on-proxmox-with-gpu-passthrough/

I setup 2 Ubunut 20.04 VMs and assigned one gpu to each of them, like shown below:
VM1 with GPU02 -> works fine
VM2 with GPU01 -> no output
The GPU in slot 02 worked fine; i could install the Nvidia driver and get the expected performance. On the other vm with the gpu on slot 01 however i didnt get any video output (no output directly on the card and vnc cant connect,which is normal)

I thought maybe there is a problem with my second vm, so i shut both down, and assigned GPU02 to VM2 and GPU01 to VM1
VM1 with GPU01 -> no output
VM2 with GPU02 -> works fine

This leads me to believe there is a problem with the configuration for the first on the proxmox server. The problem is that the whole configuration is exactly the same for both cards. They both have the same ID because they are the same model, so there is no part of the configuration that has to be done separately for the other card.
So if one is working the other one should also be working.

Any idea how to debug this? Are there any logs/files that could help with that?

 

[leesteken]

Probably the first GPU is used during boot of the Proxmox host and you need this work-around since kernel version 5.15: add initcall_blacklist=sysfb_init to the kernel parameters.

EDIT: You probably don't need anything else that other (and often out-dated) guides tell you to, but I did not bother to watch, read and correct them.

 

[niklas_t]

Probably the first GPU is used during boot of the Proxmox host and you need this work-around since kernel version 5.15: add initcall_blacklist=sysfb_init to the kernel parameters.

EDIT: You probably don't need anything else that other (and often out-dated) guides tell you to, but I did not bother to watch, read and correct them.

That solved the problem. thanks