Re: [RFC] Using SimpleDRM in the initramfs

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From	Ben Hutchings <benh@debian.org>
Newsgroups	linux.debian.kernel, linux.debian.maint.boot
Subject	Re: [RFC] Using SimpleDRM in the initramfs
Date	Mon, 11 May 2026 19:00:01 +0200
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On Mon, 2026-05-11 at 17:27 +0300, Askar Safin wrote:
> Ben Hutchings <benh@debian.org>:
> > - In the kernel, we cannot assume that an EFI framebuffer is always
> >   usable.  In particular, older versions of GRUB may break it by using
> >   a native graphics driver, but without clearing whatever signals the
> >   kernel that it is available.  This was fixed upstream in the default
> >   config for GRUB 2.14 but we cannot assume that the config change
> >   actually gets applied to existing installations.
> 
> It WILL be applied to existing installations.

That depends on just how much customisation was done.

> Here is upstream commit in question:
> https://cgit.git.savannah.gnu.org/cgit/grub.git/commit/?id=ea0b76dc4a003f2b7f828ef0c24cc8227148b2f8
> 
> It changed file util/grub.d/00_header.in in the repo. It corresponds to
> /etc/grub.d/00_header in installed system. It is script, which is used
> when generating /boot/grub/grub.cfg .
> 
> /etc/grub.d/00_header is present in output of
> "dpkg-query -W -f='${Conffiles}\n' grub-*", but I think that this is
> highly unlikely that users manually edited that file.

It is a conffile, therefore we support users modifying it.

So if we want to make a switch on upgrade we'll have to check the GRUB
configuration to figure out whether that is safe.  That's not actually
possible because the configuration is a script and not static
definitions.  The best I think we can do is "if the GRUB configuration
is unmodified from the shipped files, we can safely switch".

> So the file will be simply replaced on upgrade, and then new /boot/grub/grub.cfg
> will be generated from it.
> 
> Also note that I only was able to reproduce that GRUB bug in Qemu only.
> And I was not able to reproduce it on real hardware.
[...]

But why does that matter?  There are a lot of Debian systems running in
VMs and some fraction of those do have people looking at their graphical
output.

Ben.

-- 
Ben Hutchings - Debian developer, member of kernel, installer and LTS
teams

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Thread

[RFC] Using SimpleDRM in the initramfs Ben Hutchings <benh@debian.org> - 2026-05-10 20:50 +0200
  Re: [RFC] Using SimpleDRM in the initramfs Askar Safin <safinaskar@gmail.com> - 2026-05-11 16:50 +0200
    Re: [RFC] Using SimpleDRM in the initramfs Ben Hutchings <benh@debian.org> - 2026-05-11 19:00 +0200
  Re: [RFC] Using SimpleDRM in the initramfs Askar Safin <safinaskar@gmail.com> - 2026-05-11 18:30 +0200
    Re: [RFC] Using SimpleDRM in the initramfs Ben Hutchings <benh@debian.org> - 2026-05-11 19:10 +0200

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