linux-kernel - Re: [PATCH v2 3/6] arm64: Mark the recheduling IPI as raw interrupt

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Message-ID: <20201210151555.GB10381@willie-the-truck>
Date:   Thu, 10 Dec 2020 15:15:55 +0000
From:   Will Deacon <will@...nel.org>
To:     Marc Zyngier <maz@...nel.org>
Cc:     LAK <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Valentin Schneider <Valentin.Schneider@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@....linux.org.uk>,
        Android Kernel Team <kernel-team@...roid.com>
Subject: Re: [PATCH v2 3/6] arm64: Mark the recheduling IPI as raw interrupt

On Tue, Nov 24, 2020 at 02:14:46PM +0000, Marc Zyngier wrote:
> Flag the rescheduling IPI as 'raw', making sure such interrupt
> skips both tick management  and irqtime accounting.
> 
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> ---
>  arch/arm64/Kconfig      | 1 +
>  arch/arm64/kernel/smp.c | 4 ++++
>  2 files changed, 5 insertions(+)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 1515f6f153a0..d18c2c15848d 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -108,6 +108,7 @@ config ARM64
>  	select GENERIC_EARLY_IOREMAP
>  	select GENERIC_IDLE_POLL_SETUP
>  	select GENERIC_IRQ_IPI
> +	select ARCH_WANTS_IRQ_RAW
>  	select GENERIC_IRQ_MULTI_HANDLER
>  	select GENERIC_IRQ_PROBE
>  	select GENERIC_IRQ_SHOW
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index 18e9727d3f64..bad51f7f7ffe 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -995,6 +995,10 @@ void __init set_smp_ipi_range(int ipi_base, int n)
>  
>  		ipi_desc[i] = irq_to_desc(ipi_base + i);
>  		irq_set_status_flags(ipi_base + i, IRQ_HIDDEN);
> +
> +		/* The recheduling IPI is special... */
> +		if (i == IPI_RESCHEDULE)
> +			__irq_modify_status(ipi_base + i, 0, IRQ_RAW, ~0);

Acked-by: Will Deacon <will@...nel.org>

Although this part isn't the controversial bit :)

Will