Primary GPU displays nothing if the secondary GPU is using nouveau in a Wayland session

[Steve Langasek]

after upgrade from mantic to noble, my laptop booted to the firmware splash screen with Ubuntu logo, plus a mouse cursor. The gdm login screen did not appear.

Switching to disable wayland (as in the attached modified config file) fixed this so that the login screen appears.

ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: gdm3 46.0-2ubuntu1
ProcVersionSignature: Ubuntu 6.8.0-31.31-generic 6.8.1
Uname: Linux 6.8.0-31-generic x86_64
NonfreeKernelModules: zfs
ApportVersion: 2.28.1-0ubuntu3
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: ubuntu:GNOME
Date: Thu May 23 08:06:45 2024
InstallationDate: Installed on 2019-12-23 (1613 days ago)
InstallationMedia: Ubuntu 19.10 "Eoan Ermine" - Release amd64 (20191017)
SourcePackage: gdm3
UpgradeStatus: Upgraded to noble on 2024-05-22 (1 days ago)
mtime.conffile..etc.gdm3.custom.conf: 2024-05-22T16:33:18.326823

[Daniel van Vugt (vanvugt)]

Can you provide a journal from one of the failed boot attempts?

[Steve Langasek (vorlon)]

sorry, missed your question before, apparently my launchpad mail delivery is unreliable.

are you looking for the kernel logs, gdm service, both, something else?

[Steve Langasek (vorlon)]

Attached the kernel logs (journalctl -b0 -k --until 'May 22 16:31:05', which is when my user login under X began), plus logs for the gdm service as well as the gdm session (which seems to be where most of the actual log activity happens).

[Daniel van Vugt (vanvugt)]

It's failing to display on the integrated Intel GPU because it couldn't negotiate a pixel format that's also compatible with the discrete GPU (nouveau):

May 22 16:25:39 homer gnome-shell[4809]: Failed to lock front buffer on /dev/dri/card1: drmModeAddFB2 failed (Invalid argument) and drmModeAddFB cannot be used as a fallback because format=0x30335241 (AR30).
May 22 16:25:39 homer gnome-shell[4809]: (../clutter/clutter/clutter-frame-clock.c:495):clutter_frame_clock_notify_ready: code should not be reached

That's upstream bug https://gitlab.gnome.org/GNOME/mutter/-/issues/3389, fixed in mutter 46.1.

[Daniel van Vugt (vanvugt)]

AIUI this will only happen if there's an external monitor plugged into the discrete GPU using nouveau. That's common, but hopefully less common than hybrid laptops without an external monitor connected.

So as a workaround you should be able to:

1. Unplug the monitor.
2. Log in using the laptop display.
3. Use the 'Additional Drivers' app to install one of the proprietary Nvidia drivers.

or just use Xorg.