linux-kernel - Re: [PATCH 05/15] irq: add generic_handle_arch

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Date:   Fri, 22 Oct 2021 10:10:26 +0800
From:   Pingfan Liu <kernelfans@...il.com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     linux-kernel@...r.kernel.org, aou@...s.berkeley.edu,
        catalin.marinas@....com, deanbo422@...il.com, green.hu@...il.com,
        guoren@...nel.org, jonas@...thpole.se,
        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 05/15] irq: add generic_handle_arch_irq()

On Thu, Oct 21, 2021 at 07:02:26PM +0100, Mark Rutland wrote:
> Several architectures select GENERIC_IRQ_MULTI_HANDLER and branch to
> handle_arch_irq() without performing any entry accounting.
> 
> Add a generic wrapper to handle the commoon irqentry work when invoking
> handle_arch_irq(). Where an architecture needs to perform some entry
> accounting itself, it will need to invoke handle_arch_irq() itself.
> 
> In subsequent patches it will become the responsibilty of the entry code
> to set the irq regs when entering an IRQ (rather than deferring this to
> an irqchip handler), so generic_handle_arch_irq() is made to set the irq
> regs now. This can be redundant in some cases, but is never harmful as
> saving/restoring the old regs nests safely.
> 
> Signed-off-by: Mark Rutland <mark.rutland@....com>
> Cc: Marc Zyngier <maz@...nel.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> ---
>  kernel/irq/handle.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
> index 221d80c31e94..27182003b879 100644
> --- a/kernel/irq/handle.c
> +++ b/kernel/irq/handle.c
> @@ -14,6 +14,8 @@
>  #include <linux/interrupt.h>
>  #include <linux/kernel_stat.h>
>  
> +#include <asm/irq_regs.h>
> +
>  #include <trace/events/irq.h>
>  
>  #include "internals.h"
> @@ -226,4 +228,20 @@ int __init set_handle_irq(void (*handle_irq)(struct pt_regs *))
>  	handle_arch_irq = handle_irq;
>  	return 0;
>  }
> +
> +/**
> + * generic_handle_arch_irq - root irq handler for architectures which do no
> + *                           entry accounting themselves
> + * @regs:	Register file coming from the low-level handling code
> + */
> +asmlinkage void noinstr generic_handle_arch_irq(struct pt_regs *regs)
> +{
> +	struct pt_regs *old_regs;
> +
> +	irq_enter();
> +	old_regs = set_irq_regs(regs);
> +	handle_arch_irq(regs);

After all involved arches call generic_handle_arch_irq(), can
handle_arch_irq be encapsulated by declaring as static?

Two places need to be fixed for this purpose:
-1. absorb the logic about handle_arch_irq in arm64/kernel/irq.c
-2. In arm, setup_arch(), 
    #ifdef CONFIG_GENERIC_IRQ_MULTI_HANDLER
            handle_arch_irq = mdesc->handle_irq;
    #endif


Thanks,

	Pingfan