linux-kernel - Re: x86_64 32-bit EFI mixed mode boot broken

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Date: Mon, 1 Apr 2024 15:44:36 -0700
From: Clayton Craft <clayton@...ftyguy.net>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: Hans de Goede <hdegoede@...hat.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 regressions@...ts.linux.dev
Subject: Re: x86_64 32-bit EFI mixed mode boot broken

On Sun, 24 Mar 2024 22:53:47 +0200 Ard Biesheuvel <ardb@...nel.org> wrote:
> > > Thanks.
> > >
> > > I pushed another branch
> > >
> > > https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/log/?h=efi-clayton-3
> > >
> > > which has a proper fix for the issue that you found.
> > >
> > > As it turns out, the compat mixed mode (with handover protocol) was
> > >
> > > broken from the beginning, and the change you identified just happened
> > >
> > > to trigger it on your hardware.
> >
> >
> > Tested and fixes booting on my Bay Trail tablet and NUC. Thanks for fixing this!
> >
> > Tested-by: Clayton Craft <clayton@...ftyguy.net>

So... maybe my testing wasn't as thorough as I thought, OR I am experiencing an
unrelated problem. In any case, I'm having some difficulty figuring out what to
blame. When using this patch on the 6.6 LTS:

1) kernel seems to panic right after displaying `disabling bootcon [efifb0]`. I
determined that it's panicking by setting `panic=-1` and seeing it reboot after
showing that message. I can work around it by setting `keep_bootcon`, but that's
not ideal.

2) kernel complains about no root (from initrd). I can work around this by
passing `initrd=my-initramfs` on the kernel cmdline.

I haven't tried any newer kernels yet. The second issue above makes me wonder if
your patch related to args might be to blame, but I'm not sure. Any help poking
around further would be greatly appreciated :)

-Clayton

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