linux-kernel - Re: [PATCH 0/1] x86/kexec: UKI support

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Message-Id: <a0e1848a-4411-4a1a-82a9-5cb0080a8323@app.fastmail.com>
Date:   Mon, 11 Sep 2023 05:23:29 +0200
From:   "Jan Hendrik Farr" <kernel@...rr.cc>
To:     "Luca Boccassi" <bluca@...ian.org>
Cc:     linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
        x86@...nel.org, tglx@...utronix.de, dhowells@...hat.com,
        vgoyal@...hat.com, keyrings@...r.kernel.org,
        akpm@...ux-foundation.org, bhe@...hat.com, bhelgaas@...gle.com,
        lennart@...ttering.net
Subject: Re: [PATCH 0/1] x86/kexec: UKI support

>> > - the dtb section also is optional but supported, and given kexec
>> > supports loading a new dtb I think this change should support it too
>> > immediately.  Moreover, we are adding support for multiple DTBs in a
>> > single UKI (by simply having multiple .dtb sections, and picking the
>> > one that matches the firmware), as a stretch goal would be nice to
>> > support that too, but it can also come later
>>
>> As far as I know dtb is not supported by kexec_file_load at all at the moment. Maybe someone here knows more about this. I'll look into it.
>
> Not sure about the specific syscalls, but I definitely use kexec
> --load --dtb on arm64 with existing released versions of
> kernel/tooling

Ok, it looks like this is supported and should be doable (on arm64, not for x86). When I was looking around the source code yesterday I forgot that my LSP had indexed the kernel for x86 and not arm64.

>> > - also what would it take to support arm64, which is the other major UEFI arch?
>>
>> I'm not familiar with UEFI on arm64, but I can certainly look into it. I assume it's not gonna be that difficult.

I'll work on a separate patch for UKI support on arm64 (with .dtb section support). I think it's best to keep this x86 patch separate from that. I have a v2 patch for x86 put together with the small fix for the optional .cmdline section + a few other tweaks that I'll submit shortly.