linux-kernel - Re: [PATCH 15/15] irq: remove handle_domain

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Message-ID: <87o87hbcie.wl-maz@kernel.org>
Date:   Fri, 22 Oct 2021 11:05:29 +0100
From:   Marc Zyngier <maz@...nel.org>
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, kernelfans@...il.com,
        linux-arm-kernel@...ts.infradead.org, linux@...linux.org.uk,
        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 15/15] irq: remove handle_domain_{irq,nmi}()

On Thu, 21 Oct 2021 19:02:36 +0100,
Mark Rutland <mark.rutland@....com> wrote:
> 
> Now that entry code handles IRQ entry (including setting the IRQ regs)
> before calling irqchip code, irqchip code can safely call
> generic_handle_domain_irq(), and there's no functional reason for it to
> call handle_domain_irq().
> 
> Let's cement this split of responsibility and remove handle_domain_irq()
> entirely, updating irqchip drivers to call generic_handle_domain_irq().
> 
> For consistency, handle_domain_nmi() is similarly removed and replaced
> with a generic_handle_domain_nmi() function which also does not perform
> any entry logic.
> 
> Previously handle_domain_{irq,nmi}() had a WARN_ON() which would fire
> when they were called in an inappropriate context. So that we can
> identify similar issues going forward, similar WARN_ON_ONCE() logic is
> added to the generic_handle_*() functions, and comments are updated for
> clarity and consistency.
> 
> Signed-off-by: Mark Rutland <mark.rutland@....com>
> Cc: Marc Zyngier <maz@...nel.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>

[...]

> -/**
> - * handle_domain_nmi - Invoke the handler for a HW irq belonging to a domain
> - * @domain:	The domain where to perform the lookup
> - * @hwirq:	The HW irq number to convert to a logical one
> - * @regs:	Register file coming from the low-level handling code
> - *
> - *		This function must be called from an NMI context.
>   *
> - * Returns:	0 on success, or -EINVAL if conversion has failed
> - */
> -int handle_domain_nmi(struct irq_domain *domain, unsigned int hwirq,
> -		      struct pt_regs *regs)
> + * 		This function must be called from an NMI context with irq regs
> + * 		initialized.
> + **/
> +int generic_handle_domain_nmi(struct irq_domain *domain, unsigned int hwirq)
>  {
> -	struct pt_regs *old_regs = set_irq_regs(regs);
> -	int ret;
> -
> -	/*
> -	 * NMI context needs to be setup earlier in order to deal with tracing.
> -	 */
> -	WARN_ON(!in_nmi());
> -
> -	ret = generic_handle_domain_irq(domain, hwirq);
> -
> -	set_irq_regs(old_regs);
> -	return ret;
> +	WARN_ON_ONCE(!in_nmi());
> +	return handle_irq_desc(irq_resolve_mapping(domain, hwirq));
>  }
> -#endif
> +EXPORT_SYMBOL_GPL(generic_handle_domain_nmi);

nit: we don't need this export (only a root controller can handle
NMIs), and that's the sort of thing I would really want to avoid
exposing to modules.

	M.

-- 
Without deviation from the norm, progress is not possible.