linux-kernel - Re: [PATCH v12 7/7] arm64: smp: Mark IPI globals as __ro_after

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Date:   Thu, 31 Aug 2023 11:15:15 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     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>,
        linux-arm-kernel@...ts.infradead.org,
        Masayoshi Mizuma <msys.mizuma@...il.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Lecopzer Chen <lecopzer.chen@...iatek.com>,
        Tomohiro Misono <misono.tomohiro@...itsu.com>,
        Stephane Eranian <eranian@...gle.com>,
        kgdb-bugreport@...ts.sourceforge.net,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Stephen Boyd <swboyd@...omium.org>, ito-yuichi@...itsu.com,
        linux-perf-users@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
        D Scott Phillips <scott@...amperecomputing.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Valentin Schneider <vschneid@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v12 7/7] arm64: smp: Mark IPI globals as __ro_after_init

On Wed, Aug 30, 2023 at 12:11:28PM -0700, Douglas Anderson wrote:
> Mark the three IPI-related globals in smp.c as "__ro_after_init" since
> they are only ever set in set_smp_ipi_range(), which is marked
> "__init". This is a better and more secure marking than the old
> "__read_mostly".
> 
> Suggested-by: Stephen Boyd <swboyd@...omium.org>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
> This patch is almost completely unrelated to the rest of the series
> other than the fact that it would cause a merge conflict with the
> series if sent separately. I tacked it on to this series in response
> to Stephen's feedback on v11 of this series [1]. If someone hates it
> (not sure why they would), it could be dropped. If someone loves it,
> it could be promoted to the start of the series and/or land on its own
> (resolving merge conflicts).
> 
> [1] https://lore.kernel.org/r/CAE-0n52iVDgZa8XT8KTMj12c_ESSJt7f7A0fuZ_oAMMqpGcSzA@mail.gmail.com

This looks reasonable to me, so:

Acked-by: Mark Rutland <mark.rutland@....com>

Mark.

> 
> Changes in v12:
> - ("arm64: smp: Mark IPI globals as __ro_after_init") new for v12.
> 
>  arch/arm64/kernel/smp.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index 1a53e57c81d0..814d9aa93b21 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -84,9 +84,9 @@ enum ipi_msg_type {
>  	MAX_IPI
>  };
>  
> -static int ipi_irq_base __read_mostly;
> -static int nr_ipi __read_mostly = NR_IPI;
> -static struct irq_desc *ipi_desc[MAX_IPI] __read_mostly;
> +static int ipi_irq_base __ro_after_init;
> +static int nr_ipi __ro_after_init = NR_IPI;
> +static struct irq_desc *ipi_desc[MAX_IPI] __ro_after_init;
>  
>  static void ipi_setup(int cpu);
>  
> -- 
> 2.42.0.283.g2d96d420d3-goog
>