linux-kernel - Re: [PATCH v2 0/3] genirq: Managed affinity fixes

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Message-ID: <87a6dhxd13.wl-maz@kernel.org>
Date:   Wed, 23 Mar 2022 08:56:40 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Xiongfeng Wang <wangxiongfeng2@...wei.com>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        John Garry <john.garry@...wei.com>,
        David Decotigny <ddecotig@...gle.com>
Subject: Re: [PATCH v2 0/3] genirq: Managed affinity fixes

Hi Xiongfeng,

On Wed, 23 Mar 2022 03:52:46 +0000,
Xiongfeng Wang <wangxiongfeng2@...wei.com> wrote:
> 
> Hi, Marc
> 
> On 2022/3/22 3:36, Marc Zyngier wrote:
> > John (and later on David) reported[1] a while ago that booting with
> > maxcpus=1, managed affinity devices would fail to get the interrupts
> > that were associated with offlined CPUs.
> > 
> > Similarly, Xiongfeng reported[2] that the GICv3 ITS would sometime use
> > non-housekeeping CPUs instead of the affinity that was passed down as
> > a parameter.
> > 
> > [1] can be fixed by not trying to activate these interrupts if no CPU
> > that can satisfy the affinity is present (a patch addressing this was
> > already posted[3])
> > 
> > [2] is a consequence of affinities containing non-online CPUs being
> > passed down to the interrupt controller driver and the ITS driver
> > trying to paper over that by ignoring the affinity parameter and doing
> > its own (stupid) thing. It would be better to (a) get the core code to
> > remove the offline CPUs from the affinity mask at all times, and (b)
> > fix the drivers so that they can trust the core code not to trip them.
> > 
> > This small series, based on 5.17, addresses the above.
> 
> I have tested this patchset on D06. It works well with kernel parameter
> 'maxcpus=1' or 'nohz_full=1-127 isolcpus=nohz,domain,managed_irq,1-127'.
> Also the 'effective_affinity' is correct. Thanks!

Thanks for having given it a go.

> By the way, I merged the second patch manually because of conflicts.
> Maybe I lack some patches on your local repo.

That's odd, as the patches are directly sitting on top of 5.17 in my
tree (see [1]). Do you have any out of tree patches around? Please
make sure you test this without any extra change.

Thanks,

	M.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=irq/managed-affinity-fixes

-- 
Without deviation from the norm, progress is not possible.