linux-kernel - Re: [PATCH 10/15] irq: arm64: perform irqentry in entry code

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Message-ID: <YXbwyKeAOfIayN1A@arm.com>
Date:   Mon, 25 Oct 2021 19:00:40 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     linux-kernel@...r.kernel.org, aou@...s.berkeley.edu,
        deanbo422@...il.com, green.hu@...il.com, guoren@...nel.org,
        jonas@...thpole.se, kernelfans@...il.com,
        linux-arm-kernel@...ts.infradead.org, linux@...linux.org.uk,
        maz@...nel.org, nickhu@...estech.com, palmer@...belt.com,
        paulmck@...nel.org, paul.walmsley@...ive.com, peterz@...radead.org,
        shorne@...il.com, stefan.kristiansson@...nalahti.fi,
        tglx@...utronix.de, torvalds@...ux-foundation.org,
        tsbogend@...ha.franken.de, vgupta@...nel.org, will@...nel.org
Subject: Re: [PATCH 10/15] irq: arm64: perform irqentry in entry code

On Thu, Oct 21, 2021 at 07:02:31PM +0100, Mark Rutland wrote:
> In preparation for removing HANDLE_DOMAIN_IRQ_IRQENTRY, have arch/arm64
> perform all the irqentry accounting in its entry code.
> 
> As arch/arm64 already performs portions of the irqentry logic in
> enter_from_kernel_mode() and exit_to_kernel_mode(), including
> rcu_irq_{enter,exit}(), the only additional calls that need to be made
> are to irq_{enter,exit}_rcu(). Removing the calls to
> rcu_irq_{enter,exit}() from handle_domain_irq() ensures that we inform
> RCU once per IRQ entry and will correctly identify quiescent periods.
> 
> Since we should not call irq_{enter,exit}_rcu() when entering a
> pseudo-NMI, el1_interrupt() is reworked to have separate __el1_irq() and
> __el1_pnmi() paths for regular IRQ and psuedo-NMI entry, with
> irq_{enter,exit}_irq() only called for the former.
> 
> In preparation for removing HANDLE_DOMAIN_IRQ, the irq regs are managed
> in do_interrupt_handler() for both regular IRQ and pseudo-NMI. This is
> currently redundant, but not harmful.
> 
> For clarity the preemption logic is moved into __el1_irq(). We should
> never preempt within a pseudo-NMI, and arm64_enter_nmi() already
> enforces this by incrementing the preempt_count, but it's clearer if we
> never invoke the preemption logic when entering a pseudo-NMI.
> 
> Signed-off-by: Mark Rutland <mark.rutland@....com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Marc Zyngier <maz@...nel.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Will Deacon <will@...nel.org>

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