linux-kernel - Re: efivarfs fails with `No such device` when EFI runtime is missing

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Date:   Tue, 11 May 2021 22:58:07 +0200
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Matthew Garrett <matthew.garrett@...ula.com>,
        Jeremy Kerr <jk@...abs.org>
Cc:     linux-efi@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: efivarfs fails with `No such device` when EFI runtime is missing

[Use Ard’s current email, and add other maintainers]

Am 11.05.21 um 22:55 schrieb Paul Menzel:
> Dear Linux folks,
> 
> 
> I migrated a 32-bit GNU/Linux installation from BIOS to EFI. Trying to 
> edit the entries in UEFI’s Boot Manager with `efibootmgr`, I got the error:
> 
>     EFI variables are not supported on this system
> 
> `sudo modprobe efivarfs` fails with
> 
>     No such device
> 
> After several tries, I found
> 
>     [    0.000000] efi: No EFI runtime due to 32/64-bit mismatch with 
> kernel
> 
> logged by Linux, and then I found the Stack Overflow thread *How could 
> 32bit kernel read efivars from 64bit UEFI?* [1].
> 
> I would have thought, setting EFI variables is just directly writing to 
> some storage. But probably not.
> 
> Could the error message for the efivarfs load failure be improved, that 
> *device* means the runtime service (if I am not mistaken)?
> 
> 
> Kind regards,
> 
> Paul
> 
> 
> [1]: https://stackoverflow.com/questions/46610442/how-could-32bit-kernel-read-efivars-from-64bit-uefi