linux-kernel - Re: [PATCH v9 00/12] Support PPTT for ARM64

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Date:   Tue, 29 May 2018 21:16:24 +0100
From:   Will Deacon <will.deacon@....com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Jeremy Linton <jeremy.linton@....com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Mark Rutland <Mark.Rutland@....com>, austinwc@...eaurora.org,
        tnowicki@...iumnetworks.com, Palmer Dabbelt <palmer@...ive.com>,
        linux-riscv@...ts.infradead.org, Morten.Rasmussen@....com,
        vkilari@...eaurora.org,
        Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
        jhugo@...eaurora.org, Al Stone <ahs3@...hat.com>,
        Len Brown <lenb@...nel.org>,
        John Garry <john.garry@...wei.com>, wangxiongfeng2@...wei.com,
        Dietmar Eggemann <Dietmar.Eggemann@....com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Hanjun Guo <hanjun.guo@...aro.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH v9 00/12] Support PPTT for ARM64

Hi Geert,

On Tue, May 29, 2018 at 05:51:29PM +0200, Geert Uytterhoeven wrote:
> On Tue, May 29, 2018 at 5:08 PM, Will Deacon <will.deacon@....com> wrote:
> > On Tue, May 29, 2018 at 02:18:40PM +0100, Sudeep Holla wrote:
> >> On 29/05/18 12:56, Geert Uytterhoeven wrote:
> >> > On Tue, May 29, 2018 at 1:14 PM, Sudeep Holla <sudeep.holla@....com> wrote:
> >> >> On 29/05/18 11:48, Geert Uytterhoeven wrote:
> >> >>> System supend still works fine on systems with big cores only:
> >> >>>
> >> >>>     R-Car H3 ES1.0 (4xCA57 (4xCA53 disabled in firmware))
> >> >>>     R-Car M3-N (2xCA57)
> >> >>>
> >> >>> Reverting this commit fixes the issue for me.
> >> >>
> >> >> I can't find anything that relates to system suspend in these patches
> >> >> unless they are messing with something during CPU hot plug-in back
> >> >> during resume.
> >> >
> >> > It's only the last patch that introduces the breakage.
> >> >
> >>
> >> As specified in the commit log, it won't change any behavior for DT
> >> systems if it's non-NUMA or single node system. So I am still wondering
> >> what could trigger this regression.
> >
> > I wonder if we're somehow giving an uninitialised/invalid NUMA configuration
> > to the scheduler, although I can't see how this would happen.
> >
> > Geert -- if you enable CONFIG_DEBUG_PER_CPU_MAPS=y and apply the diff below
> > do you see anything shouting in dmesg?
> 
> Thanks, but unfortunately it doesn't help.
> I added some debug code to print cpumask, but so far I don't see anything
> suspicious.

Damn, sorry for wasting your time. For the record, Catalin's been seeing
boot failures under KVM on a non-big/LITTLE machine that bisect reliably
to this patch, but we've also not been able to explain them. Worse, adding
so much as a printk makes the problem disappear.

Will