** Description changed:
[Impact]
* In Ubuntu 20.04 (which using Xorg with proprietary nvidia driver), in some
cases, the nvidia driver will probe later than launching gdm.
* If above race condition happens in iGPU + nvidia cases and monitor
connects to dGPU, which will cause gdm starts with wayland as opposed to Xorg.
Which may lead the monitor stuck in black-screen or boot LOGO.
[Test Plan]
* The environment:
1. A desktop or workstation which containing an iGPU.
2. Plug a nvidia graphic card to the system and installing proprietary
nvidia driver (470 in my case)
3. Attach a monitor to dGPU and leave iGPU connect to nothing.
(in my test environment, there is the other ethernet card and TBT4 cards)
* Setup a cronjob,
e.g. @reboot /home/u/test.sh
* Have a test script in something like /home/u/test.sh as
#!/bin/bash
sleep 20
count="$(cat /home/ubuntu/count)"
count=$((count+1))
echo $count | tee /home/ubuntu/count
journalctl -b | grep -q -i wayland || sudo reboot
* the system will probably stuck in black-screen or boot LOGO.
* Before applying the fix, the fail rate is 6/24 (fail 6 time in 24 runs).
* After applying the fix, it got pass within 90 reboot cycles.
[Where problems could occur]
* The patch checkes device/boot_vga with tag "master-of-seat". If a system
without any GPU as boot_vga then it will wait 10 seconds in the loop.
* I tried to detach all monitors from the system and the boot_vga still
exist (default to use iGPU, the first device found during initialization)
* I don't think they will a case which boot_vga doesn't exist in this moment
because:
In drivers/gpu/vga/vgaarb.c (linux package)
vga_arb_select_default_device() has a fallback function to determine the
boot_vga device to prevent firmware doesn't pass correct efifb to linux-kernel.
---
Test environment/steps:
1. A desktop or workstation which containing an iGPU.
2. Plug a nvidia graphic card to the system and installing proprietary nvidia
driver (470 in my case)
3. Attach a monitor to dGPU and leave iGPU connect to nothing.
(in my test environment, there is the other ethernet card and TBT4 cards)
4. Reboot system.
Based on:
$ cat /lib/udev/rules.d/61-gdm.rules
# disable Wayland on Hi1710 chipsets
ATTR{vendor}=="0x19e5", ATTR{device}=="0x1711",
RUN+="/usr/lib/gdm3/gdm-disable-wayland"
# disable Wayland when using the proprietary nvidia driver
DRIVER=="nvidia", RUN+="/usr/lib/gdm3/gdm-disable-wayland"
It will disable wayland by default if proprietary nvidia driver load.
But in some race condition cases, the nvidia probe is later than gnome
launches. (The fail rate is 6/24.)
Thus, ubuntu-gdm has a fix for Bug#1794280 to add
"ExecStartPre=@libexecdir@/gdm-wait-for-drm".
The gdm-wait-for-drm is intend to make sure all drm udev devices
enumerated before launching gdm.
It rely on at least one "master-of-seat" graphic card for gdm but it's not
rigorous enough.
Since most of graphic cards are own "master-of-seat"[1].
In my case, it detects the iGPU is probed but dGPU.
However, the display is attached to dGPU.
We need to make sure the targeted gpu (connecting to monitor) is probe
before launching gdm.
+ debian bug: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1004131
+ upstream bug: https://gitlab.gnome.org/GNOME/gdm/-/issues/763
+
[1] https://www.freedesktop.org/wiki/Software/systemd/multiseat/
/lib/udev/rules.d/71-seat.rules
/lib/udev/rules.d/71-nvidia.rules
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https://bugs.launchpad.net/bugs/1958488
Title:
[nvidia][xorg] display hangs on boot LOGO
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