linux-kernel - Re: [PATCH v11 5/6] arm64: smp: IPI_CPU_STOP and IPI_CPU_CRASH

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Message-ID: <CAFA6WYPV2GWP97xaE_Mx3vUNF_xUvmsedEHr8LbJLQ+LWK-YJw@mail.gmail.com>
Date:   Tue, 29 Aug 2023 16:12:49 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Marc Zyngier <maz@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        kgdb-bugreport@...ts.sourceforge.net,
        Lecopzer Chen <lecopzer.chen@...iatek.com>,
        linux-perf-users@...r.kernel.org,
        Masayoshi Mizuma <msys.mizuma@...il.com>,
        Chen-Yu Tsai <wens@...e.org>,
        linux-arm-kernel@...ts.infradead.org, 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
Subject: Re: [PATCH v11 5/6] arm64: smp: IPI_CPU_STOP and IPI_CPU_CRASH_STOP
 should try for NMI

On Thu, 24 Aug 2023 at 21:03, Douglas Anderson <dianders@...omium.org> wrote:
>
> 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>

Reviewed-by: Sumit Garg <sumit.garg@...aro.org>

-Sumit

> ---
> I don't actually have any good way to test/validate this patch. It's
> added to the series at Mark's request.
>
> (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
>