Arch Linux

Golui

Member

Registered: 2021-11-04

Posts: 3

Non-CSM Boot - Only one GPU shows console

Hi,

I've been playing around with booting without CSM enabled in my UEFI. I'm running an AMD system without an iGPU but I have two discreet nvidia graphics cards.

Whenever I boot, only the GPU in the primary slot gets a console. The other card is displaying whatever was in the framebuffer last - the UEFI vendor logo. The kernel does not seem to respect which card I select as my primary in the UEFI settings.

Sure enough, only one framebuffer device exists; single /dev/fb0 and

cat /proc/fb

only yields

0 EFI VGA

efifb seems to only detect the card in the primary slot. I have also been unable to find reliable information on how to setup the GPU or why it fails to be captured by efifb/fbdev/fbcon - there are no errors either. It simply does not capture the PCIe device.

Things I have tried:

1. forcing textmode by disabling efifb in the kernel params

2. using uvesafb instead (seems it cannot detect the other GPU? yields "vbe_init() failed with -22")

3. configuring fbcon via kernel commandline (no relevant parameters)

4. to look for issues, I searched my dmesg with variants of "nvidia", "frame", "efi", "efifb", id of my PCI devices, "vga", "video"

My usecase is to use the primary gpu for passthrough via vfio, so it's connected to a dummy output and not really to the monitor most of the time. So far I've just been using the kernel parameters to attach to the drivers.

I should not that I have no issues with X - if I manage to blindly login I can start it no problem.

Is there a way to change what boot GPU I have on a kernel level? Perhaps another setup that could work?

EDIT: Ah, I should probably also mention that I'm using EFISTUB to launch my kernel.

Last edited by Golui (2021-11-04 20:55:59)