linux-kernel - RE: [PATCH v11 5/6] arm64: smp: IPI_CPU_STOP and IPI_CPU_CRASH_STOP should try for NMI

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Message-ID: <TYCPR01MB11025325C69AF470F2052F3B3E5E7A@TYCPR01MB11025.jpnprd01.prod.outlook.com>
Date:   Tue, 29 Aug 2023 05:30:35 +0000
From:   "Tomohiro Misono (Fujitsu)" <misono.tomohiro@...itsu.com>
To:     'Douglas Anderson' <dianders@...omium.org>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Sumit Garg <sumit.garg@...aro.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Marc Zyngier <maz@...nel.org>
CC:     "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "kgdb-bugreport@...ts.sourceforge.net" 
        <kgdb-bugreport@...ts.sourceforge.net>,
        Lecopzer Chen <lecopzer.chen@...iatek.com>,
        "linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
        Masayoshi Mizuma <msys.mizuma@...il.com>,
        Chen-Yu Tsai <wens@...e.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "Yuichi Ito (Fujitsu)" <ito-yuichi@...itsu.com>,
        Stephen Boyd <swboyd@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>,
        D Scott Phillips <scott@...amperecomputing.com>,
        Ingo Molnar <mingo@...nel.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Valentin Schneider <vschneid@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v11 5/6] arm64: smp: IPI_CPU_STOP and IPI_CPU_CRASH_STOP
 should try for NMI

> -----Original Message----- 
> There's no reason why IPI_CPU_STOP and IPI_CPU_CRASH_STOP can't be
> handled as NMI. They are very simple and everything in them is
> NMI-safe. Mark them as things to use NMI for if NMI is available.
> 
> Suggested-by: Mark Rutland <mark.rutland@....com>
> Reviewed-by: Stephen Boyd <swboyd@...omium.org>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
> I don't actually have any good way to test/validate this patch. It's
> added to the series at Mark's request.

For IPI_CPU_CRASH_STOP, I briefly checked that HARDLOCKUP-ed CPU
(by lkdtm) received the ipi upon crash dump request when pseudo NMI is
enabled.
  Reviewed-by: Misono Tomohiro <misono.tomohiro@...itsu.com>

Regards,
Tomohiro

> 
> (no changes since v10)
> 
> Changes in v10:
> - ("IPI_CPU_STOP and IPI_CPU_CRASH_STOP should try for NMI") new for
> v10.
> 
>  arch/arm64/kernel/smp.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index c8896cbc5327..4566934aaf9f 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -946,6 +946,8 @@ static bool ipi_should_be_nmi(enum ipi_msg_type ipi)
>  		return false;
> 
>  	switch (ipi) {
> +	case IPI_CPU_STOP:
> +	case IPI_CPU_CRASH_STOP:
>  	case IPI_CPU_BACKTRACE:
>  		return true;
>  	default:
> --
> 2.42.0.rc1.204.g551eb34607-goog
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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