linux-kernel - Re: [PATCH v9 20/26] irqchip/gic-v3: Handle pseudo-NMIs

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Date:   Mon, 28 Jan 2019 11:59:36 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Julien Thierry <julien.thierry@....com>
Cc:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <daniel.thompson@...aro.org>,
        <joel@...lfernandes.org>, <christoffer.dall@....com>,
        <james.morse@....com>, <catalin.marinas@....com>,
        <will.deacon@....com>, <mark.rutland@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>
Subject: Re: [PATCH v9 20/26] irqchip/gic-v3: Handle pseudo-NMIs

On Mon, 21 Jan 2019 15:33:39 +0000,
Julien Thierry <julien.thierry@....com> wrote:
> 
> Provide a higher priority to be used for pseudo-NMIs. When such an
> interrupt is received, keep interrupts fully disabled at CPU level to
> prevent receiving other pseudo-NMIs while handling the current one.
> 
> Signed-off-by: Julien Thierry <julien.thierry@....com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Jason Cooper <jason@...edaemon.net>
> Cc: Marc Zyngier <marc.zyngier@....com>
> ---
>  drivers/irqchip/irq-gic-v3.c | 42 ++++++++++++++++++++++++++++++++++++------
>  1 file changed, 36 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
> index 5374b43..4df1e94 100644
> --- a/drivers/irqchip/irq-gic-v3.c
> +++ b/drivers/irqchip/irq-gic-v3.c
> @@ -41,6 +41,8 @@
>  
>  #include "irq-gic-common.h"
>  
> +#define GICD_INT_NMI_PRI	(GICD_INT_DEF_PRI & ~0x80)
> +
>  #define FLAGS_WORKAROUND_GICR_WAKER_MSM8996	(1ULL << 0)
>  
>  struct redist_region {
> @@ -381,12 +383,45 @@ static u64 gic_mpidr_to_affinity(unsigned long mpidr)
>  	return aff;
>  }
>  
> +static inline void gic_deactivate_unexpected_irq(u32 irqnr)

Same remark as on some other patches: you should be able to drop the
inline attribute without any ill effect. I'd also like this to be
renamed "gic_deactivate_spurious", or something similar.

> +{
> +	if (static_branch_likely(&supports_deactivate_key)) {
> +		if (irqnr < 8192)
> +			gic_write_dir(irqnr);
> +	} else {
> +		gic_write_eoir(irqnr);
> +	}
> +}
> +
> +static inline void gic_handle_nmi(u32 irqnr, struct pt_regs *regs)
> +{
> +	int err;
> +
> +	if (static_branch_likely(&supports_deactivate_key))
> +		gic_write_eoir(irqnr);
> +	/*
> +	 * Leave the PSR.I bit set to prevent other NMIs to be
> +	 * received while handling this one.
> +	 * PSR.I will be restored when we ERET to the
> +	 * interrupted context.
> +	 */
> +	err = handle_domain_nmi(gic_data.domain, irqnr, regs);

So this is the point where we start having a dependency on the NMI
series. We definitely need to start talking merge strategy.

> +	if (err)
> +		gic_deactivate_unexpected_irq(irqnr);
> +}
> +
>  static asmlinkage void __exception_irq_entry gic_handle_irq(struct pt_regs *regs)
>  {
>  	u32 irqnr;
>  
>  	irqnr = gic_read_iar();
>  
> +	if (gic_supports_nmi() &&
> +	    unlikely(gic_read_rpr() == GICD_INT_NMI_PRI)) {
> +		gic_handle_nmi(irqnr, regs);
> +		return;
> +	}
> +
>  	if (gic_prio_masking_enabled()) {
>  		gic_pmr_mask_irqs();
>  		gic_arch_enable_irqs();
> @@ -403,12 +438,7 @@ static asmlinkage void __exception_irq_entry gic_handle_irq(struct pt_regs *regs
>  		err = handle_domain_irq(gic_data.domain, irqnr, regs);
>  		if (err) {
>  			WARN_ONCE(true, "Unexpected interrupt received!\n");
> -			if (static_branch_likely(&supports_deactivate_key)) {
> -				if (irqnr < 8192)
> -					gic_write_dir(irqnr);
> -			} else {
> -				gic_write_eoir(irqnr);
> -			}
> +			gic_deactivate_unexpected_irq(irqnr);
>  		}
>  		return;
>  	}
> -- 
> 1.9.1
> 

With the above addressed,

Acked-by: Marc Zyngier <marc.zyngier@....com>

	M.

-- 
Jazz is not dead, it just smell funny.