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

[Luca Boccassi <bluca@xxxxxxxxxx>]

On Sat, 9 Sept 2023 at 18:58, Jan Hendrik Farr <kernel@xxxxxxxx> wrote:
>
> > - the cmdline section is actually optional, just like it's optional to
> > pass it on a traditional kexec load, so it should be used if present,
> > but skipped if not
>
> Should be an easy fix.
>
> This should be updated in the UKI documentation as for other optional sections it's explicitly marked. I assumed that in the case of an empty cmdline the section would still be included but empty. Or is that semantically different: empty .cmdline section -> no cmdline allowed, no .cmdline section -> user can specify cmdline in bootloader?

Yeah the doc is wrong, tools handle it as optional, fixing the docs:
https://github.com/uapi-group/specifications/pull/72

> > - 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

> > - 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.