linux-kernel - Re: [PATCH v3 03/16] arm64: Allow IPIs to be handled as normal interrupts

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Message-ID: <20200911150539.GD12835@gaia>
Date:   Fri, 11 Sep 2020 16:05:39 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Will Deacon <will@...nel.org>,
        Russell King <linux@....linux.org.uk>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Sumit Garg <sumit.garg@...aro.org>,
        Valentin Schneider <Valentin.Schneider@....com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Andrew Lunn <andrew@...n.ch>,
        Saravana Kannan <saravanak@...gle.com>, kernel-team@...roid.com
Subject: Re: [PATCH v3 03/16] arm64: Allow IPIs to be handled as normal
 interrupts

On Tue, Sep 01, 2020 at 03:43:11PM +0100, Marc Zyngier wrote:
> In order to deal with IPIs as normal interrupts, let's add
> a new way to register them with the architecture code.
> 
> set_smp_ipi_range() takes a range of interrupts, and allows
> the arch code to request them as if the were normal interrupts.
> A standard handler is then called by the core IRQ code to deal
> with the IPI.
> 
> This means that we don't need to call irq_enter/irq_exit, and
> that we don't need to deal with set_irq_regs either. So let's
> move the dispatcher into its own function, and leave handle_IPI()
> as a compatibility function.
> 
> On the sending side, let's make use of ipi_send_mask, which
> already exists for this purpose.
> 
> One of the major difference is that we end up, in some cases
> (such as when performing IRQ time accounting on the scheduler
> IPI), end up with nested irq_enter()/irq_exit() pairs.
> Other than the (relatively small) overhead, there should be
> no consequences to it (these pairs are designed to nest
> correctly, and the accounting shouldn't be off).
> 
> Reviewed-by: Valentin Schneider <valentin.schneider@....com>
> Signed-off-by: Marc Zyngier <maz@...nel.org>

In case you need an ack for the arm64 part:

Acked-by: Catalin Marinas <catalin.marinas@....com>