[focal] Wayland session is not available when a laptop has an Nvidia card an Intel card is in use

[Dmitrii Shcherbakov]

A Wayland session present at /usr/share/wayland-sessions/ubuntu-wayland.desktop is not displayed at the login screen when a system has an iGPU (Intel) and dGPU (Nvidia) and Intel iGPU is used:

prime-select query
intel

Only sessions at /usr/share/xsessions are present.

➜ ~ ls /usr/share/xsessions
remmina-gnome.desktop ubuntu.desktop

➜ ~ ls /usr/share/wayland-sessions
ubuntu-wayland.desktop

The root cause is the existence of a udev rule in 61-gdm.rules that runs gdm-disable-wayland when an nvidia driver is loaded in combination with LP: #1848326 (see this comment specifically https://bugs.launchpad.net/ubuntu/+source/nvidia-prime/+bug/1848326/comments/7).

dpkg -S /lib/udev/rules.d/61-gdm.rules
gdm3: /lib/udev/rules.d/61-gdm.rules

grep nvidia /lib/udev/rules.d/61-gdm.rules
# disable Wayland when using the proprietary nvidia driver
DRIVER=="nvidia", RUN+="/usr/lib/gdm3/gdm-disable-wayland"

When I comment it out and reboot, I get the right menu entry and am able to observe the right session type:

➜ ~ grep nvidia /lib/udev/rules.d/61-gdm.rules
# disable Wayland when using the proprietary nvidia driver
#DRIVER=="nvidia", RUN+="/usr/lib/gdm3/gdm-disable-wayland"

➜ ~ loginctl
SESSION UID USER SEAT TTY
      2 1000 dima seat0 tty2

1 sessions listed.

➜ ~ loginctl show-session 2 -p Type
Type=wayland

System info:

lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu Focal Fossa (development branch)
Release: 20.04
Codename: focal

➜ ~ dpkg -l | grep gdm3
ii gdm3 3.34.1-1ubuntu1 amd64 GNOME Display Manager

➜ ~ dpkg -l | grep nvidia-prime
ii nvidia-prime 0.8.13 all Tools to enable NVIDIA's Prime

➜ ~ dpkg -l | grep nvidia-driver
ii nvidia-driver-440 440.59-0ubuntu1 amd64 NVIDIA driver metapackage

[Daniel van Vugt (vanvugt)]

Thanks for the bug report.

That udev rule causing the problem is unfortunately something that upstream won't let us replace. I have tried replacing it with smarter mutter logic and (so far) it's been rejected:

https://gitlab.gnome.org/GNOME/mutter/merge_requests/625

[Daniel van Vugt (vanvugt)]

Although we can always try again and search for a third solution, if you would like to open a new bug upstream?

https://gitlab.gnome.org/GNOME/gdm/issues

[Dmitrii Shcherbakov (dmitriis)]

Hi Daniel, thank you for the quick response and prior work.

I think the upstream check for the nvidia driver in 61-gdm.rules is too broad to be useful as the nvidia driver might be loaded for other reasons (e.g. CUDA usage or hw accelerated video encoding/decoding while nvidia-drm.ko is blacklisted) so I believe I can come up with an issue upstream.

[Daniel van Vugt (vanvugt)]

BTW, we don't want to remove the udev rule because removing it causes a bigger problem for more people: bug 1705369

So a general fix like https://gitlab.gnome.org/GNOME/mutter/merge_requests/625 would need to exist before the udev rule can be removed.

[Dmitrii Shcherbakov (dmitriis)]

I see, thanks for the clarification.

I will need to read through other cases as well.

[Sebastien Bacher (seb128)]

The wayland session isn't a critical feature, that doesn't need to be rls tracked

[Launchpad Janitor (janitor)]

[Expired for gdm3 (Ubuntu) because there has been no activity for 60 days.]