Bug 32028

Summary:	Kernel command line vga= setting to be reconsidered.
Product:	Mageia	Reporter:	Morgan Leijström <fri>
Component:	Installer	Assignee:	Mageia tools maintainers <mageiatools>
Status:	NEW ---	QA Contact:
Severity:	normal
Priority:	Normal	CC:	ghibomgx, kernel
Version:	Cauldron
Target Milestone:	Mageia 10
Hardware:	All
OS:	Linux
Whiteboard:
Source RPM:	drakxtools	CVE:
Status comment:

Description Morgan Leijström 2023-06-19 22:55:10 CEST

Description of problem:

When vga= is set too high, with proprietary nvidia drivers, virtual tty may render plain black, and shifting back and forth lead to hard hang -> possible data corruption and loss.

See Bug 31994

I only know that reducing this resolution made it work on my system.

There may be better methods.

I open this bug so it can be considered.

Morgan Leijström 2023-06-19 22:55:34 CEST

CC: (none) => kernel
Assignee: bugsquad => mageiatools

Comment 1 Morgan Leijström 2023-06-19 23:05:26 CEST

Our installer had on my system set vga=797 which is by the table at
 https://en.wikipedia.org/wiki/VESA_BIOS_Extensions#Linux_video_mode_numbers
not a fully supported mode.

Comment 2 Morgan Leijström 2023-06-19 23:08:22 CEST

If that table is valid, I think we should only set non guaranteed values for drivers that we know support that mode, but how can we tell?  And reconsider it every time a driver is updated or another driver is chosen.

Comment 3 Giuseppe Ghibò 2023-06-20 01:35:51 CEST

(In reply to Morgan Leijström from comment #1)

> Our installer had on my system set vga=797 which is by the table at
>  https://en.wikipedia.org/wiki/VESA_BIOS_Extensions#Linux_video_mode_numbers
> not a fully supported mode.

The modes seems to be defined here, from line 19 to 35:

https://gitweb.mageia.org/software/drakx-kbd-mouse-x11/tree/lib/Xconfig/resolution_and_depth.pm

apparently mode 777 (1600x1200x8), 796 (1600x1200x15) and 797 (1600x1200x16) are non-standard.

mode 786 (640x480x24), 789 (800x600x24), 792 (1024x768x24), 795 (1280x1024x24) seems missed (though there isn't any 24bit depth mode listed, so I wonder if that is on purpose).

I'd simply try removing non-standard modes, and eventually add those 4 missed.

CC: (none) => ghibomgx

Comment 4 Thomas Backlund 2023-06-20 01:46:10 CEST

drakx list is outdated...

kernel framebuffer nowdays knows modes all the way up to 2560x1600, and kms can run in native mode atleast up to 4K mode

Comment 5 Thomas Backlund 2023-06-20 01:51:33 CEST

Anyway, reworking drakx stuff is only allowed for mga10, codebase is considered in release freeze for mga9

Target Milestone: --- => Mageia 10

Comment 6 Giuseppe Ghibò 2023-06-20 01:52:36 CEST

in kms it was reported (e.g. arch docs) that the "vga=<...>" option need to be removed completely as it conflicts with the native resolution enabled in kms. Does it conflicts?

Then there is also the GRUB_GFXMODE=<...> in /etc/default/grub.