Re: [PATCH v6 00/21] Add support for 32-bit tasks on asymmetric AArch32 systems

From: Qais Yousef
Date: Fri May 21 2021 - 13:45:49 EST

Hi Will

On 05/18/21 10:47, Will Deacon wrote:
> Hi folks,
> This is the long-awaited v6 of these patches which I last posted at the
> end of last year:
> v1:
> v2:
> v3:
> v4:
> v5:
> There was also a nice LWN writeup in case you've forgotten what this is
> about:
> It's taken me a while to get a v6 of this together, partly due to
> addressing the review feedback on v5, but also because this has now seen
> testing on real hardware which threw up some surprises in suspend/resume,
> SCHED_DEADLINE and compat hwcap reporting. Thanks to Quentin for helping
> me to debug those issues.
> The aim of this series is to allow 32-bit ARM applications to run on
> arm64 SoCs where not all of the CPUs support the 32-bit instruction set.
> Unfortunately, such SoCs are real and will continue to be productised
> over the next few years at least. I can assure you that I'm not just
> doing this for fun.
> Changes in v6 include:
> * Save/restore the affinity mask across execve() to 32-bit and back to
> 64-bit again.
> * Allow 32-bit deadline tasks, but skip straight to fallback path when
> determining new affinity mask on execve().
> * Fixed resume-from-suspend path when the resuming CPU is 64-bit-only
> by deferring wake-ups for 32-bit tasks until the secondary CPUs are
> back online.
> * Bug fixes (compat hwcaps, memory leak, cpuset fallback path).
> * Documentation for arm64. It's in the divisive .rst format, but please
> take a look anyway!
> I'm pretty happy with this now and it seems to do the right thing,
> although the new patches in this revision would certainly benefit from
> review. Series based on v5.13-rc1.

It's late Fri and I'm off next week (I'm starting to sense an omen here, it's
the 2nd or 3rd time the post syncs with my holiday), so a bit of a rushed
review but the series looks good to me. Feel free to stick my Reviewed-by for
the series, except patch 13 where I skipped it, given the few comments I had
are addressed.

I did test v5, but not this version. I think it had found better victims to
test it now :-P


Qais Yousef