Multi-monitor support broken

[catfromplan9]

Component

Dasharo firmware

Device

MSI Pro Z690-A

Dasharo version

v1.1.4

Dasharo Tools Suite version

No response

Test case ID

No response

Brief summary

When using Xorg (Wayland too? untested), multi monitor output is broken.

How reproducible

It always occurs, 100% of the time, tested with and without option ROM loading enabled. I have not been able to test the iGPU because the motherboard lacks a secondary display output.

How to reproduce

Flash stock MSI BIOS and set up a multi monitor Xorg configuration. Use a window manager, any works. I have personally tested windowmaker, dwm, motif, and i3 and observed this in all of them. Flash dasharo and observe aforementioned behavior, without any additional changes made to the Xorg config.

Expected behavior

Assuming the window manager was compiled with libXinerama support, each display has its own bounds and function independently of eachother. When executing a full screen application, it will consume the entirety of one monitor but not extend beyond that point. On a tiling window manager, tiling will occur within the bounds of the monitor in which it operates, and will not extend outside of this boundary unless it is set to floating mode and dragged outside of the boundary by the user.

Actual behavior

The window manager will treat both monitors as one very wide monitor. Of the two, the one with a larger height will be used to determine how tall this virtual display should be. It should be noted, however, that in xrandr both monitors appear independent as they always would. For visual demonstration, you can recompile a window manager without Xinerama support (dwm is very easy to disable Xinerama on), and notice the effect when two monitors are connected.

Screenshots

No response

Additional context

I have confirmed that this is an issue not with my Xorg config but with dasharo/coreboot on this board. I have confirmed multi monitor to not work, and subsequently flashed the stock MSI BIOS directly afterward, at which point it works as expected again. I believe this is a problem in this board's UEFI GOP implementation.

Solutions you've tried

I have tried reconfiguring my xorg.conf similarly to what has been suggested here https://bbs.archlinux.org/viewtopic.php?pid=1381020#p1381020

On the stock BIOS, though I am using a multiGPU system, the change suggested in that forum post was not necessary. The secondary GPU is passed through vfio-pci regardless, so I don't see how this could cause troubles. I have also confirmed this issue to occur when only one gpu is present in the system, so that is unrelated.