On Wed, Oct 15, 2025 at 05:16:05PM +0200, Gerd Hoffmann wrote:
> On Wed, Oct 15, 2025 at 03:30:53PM +0200, Daniel Kiper via Grub-devel wrote:
> > On Tue, Oct 14, 2025 at 10:17:45AM -0500, Andrew Hamilton wrote:
> > > Daniel - can you take a look at this one to see if we can get it pulled 
> > > in to
> > > help those affected by this issue?
> >
> > I am not entirely sure it [1] is correct.
>
> Well.  Underlying problem is that there are two drivers active for one
> piece of hardware.  The driver which comes with the EFI firmware, and
> the grub driver.  Which is /never/ a good idea.  In this specific case
> the effect is very visible, with other hardware the problems can be more
> obscure or with luck not present.
>
> The by far easiest way to handle this properly to allow only the efi_*
> drivers on all EFI platforms.  The patch does just that (limited to
> video drivers).
>
> Alternatively you can check for conflicts.  Check which physical device
> backs efi_gop, block that from being used by grub drivers.  Same for
> all other device types.
>
> The latter would handle the corner case that there is hardware which is
> (a) supported by grub, and (b) not supported by the firmware, and (c)
> essential to boot the system.  Not sure how relevant that is in
> practice, most EFI firmware I've seen recently is pretty complete when
> it comes to hardware support.  NIC drivers are missing sometimes, iPXE
> to the rescue ;)
>
> Note that the same conflict exists for filesystem drivers too, usually
> both EFI and grub FAT drivers are active.  Luckily write access to
> the ESP is very rare, so this isn't much of a problem in practice.

I am not saying it is not a problem. I rather saying that I do not like
the solution. Or even we... I discussed the issue with Vladimir and he
agrees with me.

Anyway, why cannot you use GRUB_VIDEO_BACKEND config variable?
If it is not acceptable please propose a solution without disabling
drivers currently build and provided by the GRUB. We are OK with not
loading some drivers but we are against disabling them at build.

Daniel

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