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

[Luca Boccassi <bluca@xxxxxxxxxx>]

On Sat, 9 Sept 2023 at 17:19, Jan Hendrik Farr <kernel@xxxxxxxx> wrote:
>
> Hello,
>
> this patch implements UKI support for kexec_file_load. It will require support
> in the kexec-tools userspace utility. For testing purposes the following can be used:
> https://github.com/Cydox/kexec-test/
>
> There has been discussion on this topic in an issue on GitHub that is linked below
> for reference.
>
>
> Some links:
> - Related discussion: https://github.com/systemd/systemd/issues/28538
> - Documentation of UKIs: https://uapi-group.org/specifications/specs/unified_kernel_image/
>
> Jan Hendrik Farr (1):
>   x86/kexec: UKI support

Hi,

Thanks for working on this, it looks super useful and at Microsoft we
are definitely interested in it, as we rely heavily on kexec and we
are looking to switch to UKIs.

I had a quick look, two comments:

- 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
- 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
- also what would it take to support arm64, which is the other major UEFI arch?