XPost: linux.debian.bugs.dist   
   From: carnil@debian.org   
      
   Hi,   
      
   On Sun, Dec 21, 2025 at 07:23:43AM +0100, Salvatore Bonaccorso wrote:   
   > Control: tags -1 + upstream moreinfo   
   >   
   > On Sat, Dec 20, 2025 at 11:05:18PM +0100, Thorsten Glaser wrote:   
   > > Package: src:linux   
   > > Version: 5.10.247-1   
   > > Severity: important   
   > > X-Debbugs-Cc: tg@mirbsd.de   
   > >   
   > > After an upgrade from 5.10.0-36 to -37, the virtual consoles   
   > > 2-12 are unusable: they merely show a screenful of the old   
   > > currency sign (which seems to be the replacement character   
   > > for some reason, but I believe it’s U+00A4), and when I enter   
   > > text, it mostly stays like that, except for one space that   
   > > moves around the screen and a lowercase x that appears near   
   > > the beginning of a line.   
   > >   
   > > Virtual console 1 is fully usable.   
   >   
   > Please see   
   > https://lists.debian.org/debian-kernel/2025/12/msg00211.html .   
   >   
   > If you can do the bisect mentioned that would help identifying the   
   > problem.   
      
   I just realized I had a copy paste error in my proceure there, so   
   obvoulsy the second git checkout would be v5.10.247. For consistencly   
   let's replicate it here:   
      
       git clone --single-branch -b linux-5.10.y https://git.kernel   
   org/pub/scm/linux/kernel/git/stable/linux-stable.git   
       cd linux-stable   
       git checkout v5.10.244   
       cp /boot/config-$(uname -r) .config   
       yes '' | make localmodconfig   
       make savedefconfig   
       mv defconfig arch/x86/configs/my_defconfig   
      
       # test 5.10.244 to ensure this is "good"   
       make my_defconfig   
       make -j $(nproc) bindeb-pkg   
       ... install the resulting .deb package and confirm it successfully boots /   
   problem does not exist   
      
       # test 5.10.247 to ensure this is "bad"   
       git checkout v5.10.247   
       make my_defconfig   
       make -j $(nproc) bindeb-pkg   
       ... install the resulting .deb package and confirm it fails to boot /   
   problem exists   
      
   With that confirmed, the bisection can start:   
      
       git bisect start   
       git bisect good v5.10.244   
       git bisect bad v5.10.247   
      
   In each bisection step git checks out a state between the oldest   
   known-bad and the newest known-good commit. In each step test using:   
      
       make my_defconfig   
       make -j $(nproc) bindeb-pkg   
       ... install, try to boot / verify if problem exists   
      
   and if the problem is hit run:   
      
       git bisect bad   
      
   and if the problem doesn't trigger run:   
      
       git bisect good   
      
   . Please pay attention to always select the just built kernel for   
   booting, it won't always be the default kernel picked up by grub.   
      
   Iterate until git announces to have identified the first bad commit.   
      
   Then provide the output of   
      
       git bisect log   
      
   In the course of the bisection you might have to uninstall previous   
   kernels again to not exhaust the disk space in /boot. Also in the end   
   uninstall all self-built kernels again.   
      
   If we can identify a breaking commit that would be then easy enough to   
   forward upstream. I nparticular we should make as well sure if this is   
   a 5.10.y specific regresssion (but I have not seen the behaviour   
   reported on other kernels).   
      
   Regards   
   Salvatore   
      
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