Bug 15161

Summary: qemuarm/nodistro/ linux-yocto 6.4 fails parselogs
Product: [Build System, Metadata & Runtime] OE-Core Reporter: Ross Burton <ross.burton>
Component: kernelAssignee: Ross Burton <ross.burton>
Status: RESOLVED FIXED QA Contact:
Severity: normal    
Priority: High CC: jdmason, jon.mason, randy.macleod, tom.zanussi
Version: 4.3   
Target Milestone: 4.3 M3   
Hardware: x86   
OS: Multiple   
Whiteboard:
OS type for building Yocto: --- Type of Regression: ---
Verified: Documentation change: No (bug/feature does not impact docs)

Description Ross Burton 2023-07-14 13:07:54 UTC 
Since linux-yocto upgraded to 6.4, qemuarm for nodistro fails in testimage's parselogs because the virtio framebuffer doesn't behave as before:


[    49.134] (DB) xf86MergeOutputClassOptions unsupported bus type 0
[    49.138] (II) FBDEV(0): checking modes against framebuffer device...
[    49.144] (II) FBDEV(0): 	mode "640x480" test failed
[    49.148] (II) FBDEV(0): 	mode "640x480" test failed
[    49.153] (II) FBDEV(0): 	mode "640x480" test failed
[    49.157] (II) FBDEV(0): 	mode "640x480" test failed
[    49.159] (II) FBDEV(0): 	mode "640x480" not found

Interestingly it works with poky, so presumably enabling GL in xserver results in a different codepath.
Comment 1 Ross Burton 2023-07-21 16:22:41 UTC 
Jon bisected the kernel change down to:

commit ee4cce0a8f03a3332ccf48ef8b420a65d02d1fcf (refs/bisect/bad)
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Tue Apr 4 21:40:38 2023 +0200
    drm/fb-helper: fix input validation gaps in check_var
    Apparently drivers need to check all this stuff themselves, which for
    most things makes sense I guess. And for everything else we luck out,
    because modern distros stopped supporting any other fbdev drivers than
    drm ones and I really don't want to argue anymore about who needs to
    check stuff. Therefore fixing all this just for drm fbdev emulation is
    good enough.
    Note that var->active is not set or validated. This is just control
    flow for fbmem.c and needs to be validated in there as needed.
    Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
    Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
    Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
    Cc: Maxime Ripard <mripard@kernel.org>
    Cc: Thomas Zimmermann <tzimmermann@suse.de>
    Link: https://patchwork.freedesktop.org/patch/msgid/20230404194038.472803-3-daniel.vetter@ffwll.ch
Comment 2 Jon Mason 2023-07-24 14:45:42 UTC 
It appears that this patch is zero'ing variables that were not touched previous, which is causing the issue.  Specifically in __fill_var, 

       var->left_margin = var->right_margin = 0;
       var->upper_margin = var->lower_margin = 0;
       var->hsync_len = var->vsync_len = 0;


if those lines are removed, then it is happy again.  The investigation as to why this was changed continues
Comment 3 Ross Burton 2023-08-10 14:52:13 UTC 
Fixed in oe-core 366d7876a70ab8833ccc0cb6607aac7e8a0311b8.