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

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Date: Thu, 21 Mar 2024 17:06:41 -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 Thu, 21 Mar 2024 23:48:09 +0100 Ard Biesheuvel <ardb@...nel.org> wrote:
> > v6.8 fails for me, and presumably so does everything back to v6.2. v6.1 is able
> > to boot OK on these platforms with mixed mode, and it looks like there are a lot
> > of changes from 6.1..6.2 for EFI/mixed mode booting.
> 
> v6.1 just received some EFI related backports, so please check the
> latest v6.1.y as well.

I just gave v6.1.82 a try, and it fails to boot for me. That seems to be a
regression from the 6.1.0 that I tested previously.

> I usually test on 32-bit OVMF built with LOAD_X64_ON_IA32_ENABLE,
> which allows the use of the compat entry point. This is different from
> the EFI handover protocol, and I am not sure which one you are using.

I should have mentioned this previously, here's the EFI-related kconfig that I
am using. If there's anything missing then please let me know:

        CONFIG_EFI=y
        CONFIG_EFI_EARLYCON=y
        CONFIG_EFI_ESRT=y
        # CONFIG_EFI_HANDOVER_PROTOCOL is not set
        CONFIG_EFI_MIXED=y
        CONFIG_EFI_RUNTIME_WRAPPERS=y
        CONFIG_EFI_STUB=y
        CONFIG_EFI_VARS_PSTORE=m
        CONFIG_EFI_VARS_PSTORE_DEFAULT_DISABLE=y

Note that the EFI handover protocol support is disabled, I was under the
impression that it's not required for mixed mode.

Please let me know if there's any more information I can provide about my
testing / setup.

-Clayton

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