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

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Date:   Mon, 24 May 2021 23:08:51 +0100
From:   Will Deacon <will@...nel.org>
To:     Qais Yousef <qais.yousef@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Quentin Perret <qperret@...gle.com>, Tejun Heo <tj@...nel.org>,
        Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>, kernel-team@...roid.com
Subject: Re: [PATCH v6 00/21] Add support for 32-bit tasks on asymmetric
 AArch32 systems

On Fri, May 21, 2021 at 06:45:42PM +0100, Qais Yousef wrote:
> 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: https://lore.kernel.org/r/20201027215118.27003-1-will@kernel.org
> >   v2: https://lore.kernel.org/r/20201109213023.15092-1-will@kernel.org
> >   v3: https://lore.kernel.org/r/20201113093720.21106-1-will@kernel.org
> >   v4: https://lore.kernel.org/r/20201124155039.13804-1-will@kernel.org
> >   v5: https://lore.kernel.org/r/20201208132835.6151-1-will@kernel.org
> > 
> > There was also a nice LWN writeup in case you've forgotten what this is
> > about:
> > 
> > 	https://lwn.net/Articles/838339/
> > 
> > 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.

Thanks, Qais. I'm planning a v7 with quite a few changes, so it's probably
best if you offer your Reviewed-by on individual patches when you're happy
with them rather than me adding it to code that I'm still tweaking. But
thanks for the offer!

Have a good week off,

Will