Re: Question about loading bare metal firmware

["Alex Bennée" <alex.bennee@linaro.org>]

Clément Chigot <chigot@adacore.com> writes:

> Hi all,
>
> I'm wondering if there is an official way to load bare metal software
> within qemu emulations.
> I've seen a lot of people (including us) using -kernel. However, the
> doc seems to imply that the generic loader would be a better approach
> (cf [1]). I know that the compatibility with older Qemus is one of the
> reasons why -kernel is still highly used. I've also seen that the
> reset vector can be initialized automatically by -kernel unlike with
> the generic loader (this is the case with RiscV AFAICT).
> But is there any kind of official recommendation on that topic ?

The recommendation is in the document you linked. For bare metal use the
generic loader and make sure you put the blob in the right place so the
architectural reset vector will jump to it.

> I'm asking that because a recent change in RiscV Polarfire Soc is
> forcing -dtb to be passed along -kernel. But in case of bare board
> software, -dtb isn't needed (at least in our use case).
> I've a patch that allows "-dtb" to be missing with "-kernel" only if
> "-bios none" is provided. But I'm not sure if this is the right way to
> say "it's a bare board software".
>
> @Bin Meng you're the one that added this -kernel support in PolarFire
> Soc. Thus, is my approach looking good for you or do you have a better
> one in mind ?
>
> [1] https://www.qemu.org/docs/master/system/qemu-manpage.html#hxtool-8
>
> Thanks,
> Clément


-- 
Alex Bennée