Date:   Tue, 31 Jul 2018 20:11:04 -0700
From:   Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To:     Julien Thierry <julien.thierry@....com>
Cc:     linux-kernel@...r.kernel.org, tglx@...utronix.de,
        peterz@...radead.org, marc.zyngier@....com, mingo@...nel.org
Subject: Re: [PATCH 2/4] genirq: Provide NMI management for percpu_devid
 interrupts

On Tue, Jul 24, 2018 at 12:07:05PM +0100, Julien Thierry wrote:
> Add support for percpu_devid interrupts treated as NMIs.
> 
> Percpu_devid NMIs need to be setup/torn down on each CPU they target.
> 
> The same restrictions as for global NMIs still apply for percpu_devid NMIs.
> 
> Signed-off-by: Julien Thierry <julien.thierry@....com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Marc Zyngier <marc.zyngier@....com>
> ---
>  include/linux/interrupt.h |   9 +++
>  kernel/irq/manage.c       | 149 ++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 158 insertions(+)
> 
> diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
> index 3b1a320..59d3877 100644
> --- a/include/linux/interrupt.h
> +++ b/include/linux/interrupt.h
> @@ -168,10 +168,15 @@ struct irqaction {
>  				    devname, percpu_dev_id);
>  }
>  
> +extern int __must_check
> +request_percpu_nmi(unsigned int irq, irq_handler_t handler,
> +		   const char *devname, void __percpu *dev);
> +
>  extern const void *free_irq(unsigned int, void *);
>  extern void free_percpu_irq(unsigned int, void __percpu *);
>  
>  extern const void *free_nmi(unsigned int irq, void *dev_id);
> +extern void free_percpu_nmi(unsigned int irq, void __percpu *percpu_dev_id);
>  
>  struct device;
>  
> @@ -224,7 +229,11 @@ struct irqaction {
>  extern void irq_wake_thread(unsigned int irq, void *dev_id);
>  
>  extern void disable_nmi_nosync(unsigned int irq);
> +extern void disable_percpu_nmi(unsigned int irq);

Shouldn't this be a disable_percpu_nmi_nosync() as disable_nmi_nosync()?

>  extern void enable_nmi(unsigned int irq);
> +extern void enable_percpu_nmi(unsigned int irq, unsigned int type);
> +extern int ready_percpu_nmi(unsigned int irq);
> +extern void teardown_percpu_nmi(unsigned int irq);
>  
>  /* The following three functions are for the core kernel use only. */
>  extern void suspend_device_irqs(void);
> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
> index 3b87143..ad41c4d 100644
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -2162,6 +2162,11 @@ void enable_percpu_irq(unsigned int irq, unsigned int type)
>  }
>  EXPORT_SYMBOL_GPL(enable_percpu_irq);
>  
> +void enable_percpu_nmi(unsigned int irq, unsigned int type)
> +{
> +	enable_percpu_irq(irq, type);
> +}
> +
>  /**
>   * irq_percpu_is_enabled - Check whether the per cpu irq is enabled
>   * @irq:	Linux irq number to check for
> @@ -2201,6 +2206,11 @@ void disable_percpu_irq(unsigned int irq)
>  }
>  EXPORT_SYMBOL_GPL(disable_percpu_irq);
>  
> +void disable_percpu_nmi(unsigned int irq)
> +{
> +	disable_percpu_irq(irq);
> +}
> +
>  /*
>   * Internal function to unregister a percpu irqaction.
>   */
> @@ -2232,6 +2242,8 @@ static struct irqaction *__free_percpu_irq(unsigned int irq, void __percpu *dev_
>  	/* Found it - now remove it from the list of entries: */
>  	desc->action = NULL;
>  
> +	desc->istate &= ~IRQS_NMI;
> +
>  	raw_spin_unlock_irqrestore(&desc->lock, flags);
>  
>  	unregister_handler_proc(irq, action);
> @@ -2285,6 +2297,19 @@ void free_percpu_irq(unsigned int irq, void __percpu *dev_id)
>  }
>  EXPORT_SYMBOL_GPL(free_percpu_irq);
>  
> +void free_percpu_nmi(unsigned int irq, void __percpu *dev_id)
> +{
> +	struct irq_desc *desc = irq_to_desc(irq);
> +
> +	if (!desc || !irq_settings_is_per_cpu_devid(desc))
> +		return;
> +
> +	if (WARN_ON(!(desc->istate & IRQS_NMI)))
> +		return;
> +
> +	kfree(__free_percpu_irq(irq, dev_id));
> +}
> +
>  /**
>   *	setup_percpu_irq - setup a per-cpu interrupt
>   *	@irq: Interrupt line to setup
> @@ -2375,6 +2400,130 @@ int __request_percpu_irq(unsigned int irq, irq_handler_t handler,
>  EXPORT_SYMBOL_GPL(__request_percpu_irq);
>  
>  /**
> + *	request_percpu_nmi - allocate a percpu interrupt line for NMI delivery
> + *	@irq: Interrupt line to allocate
> + *	@handler: Function to be called when the IRQ occurs.
> + *	@devname: An ascii name for the claiming device
> + *	@dev_id: A percpu cookie passed back to the handler function
> + *
> + *	This call allocates interrupt resources and enables the
> + *	interrupt on the local CPU. If the interrupt is supposed to be
> + *	enabled on other CPUs, it has to be done on each CPU using
> + *	enable_percpu_nmi().
> + *
> + *	Dev_id must be globally unique. It is a per-cpu variable, and
> + *	the handler gets called with the interrupted CPU's instance of
> + *	that variable.
> + *
> + *	Interrupt lines requested for NMI delivering should have auto enabling
> + *	setting disabled.
> + *
> + *	If the interrupt line cannot be used to deliver NMIs, function
> + *	will fail returning a negative value.
> + */
> +int request_percpu_nmi(unsigned int irq, irq_handler_t handler,
> +		       const char *name, void __percpu *dev_id)
> +{
> +	struct irqaction *action;
> +	struct irq_desc *desc;
> +	unsigned long flags;
> +	int retval;
> +
> +	if (!handler)
> +		return -EINVAL;
> +
> +	desc = irq_to_desc(irq);
> +
> +	if (!desc || !irq_settings_can_request(desc)
> +	    || !irq_settings_is_per_cpu_devid(desc)
> +	    || irq_settings_can_autoenable(desc)
> +	    || !irq_supports_nmi(desc))

Shouldn't the logical operators go at the end of the line in a multi-line
statement?

> +		return -EINVAL;
> +
> +	/* The line cannot already be NMI */
> +	if (desc->istate & IRQS_NMI)
> +		return -EINVAL;
> +
> +	action = kzalloc(sizeof(struct irqaction), GFP_KERNEL);
> +	if (!action)
> +		return -ENOMEM;
> +
> +	action->handler = handler;
> +	action->flags = IRQF_PERCPU | IRQF_NO_SUSPEND | IRQF_NO_THREAD
> +		| IRQF_NOBALANCING;

Shouldn't IRQF_NOBALANCING be aligned with IRQF_PERCPU;

Thanks and BR,
Ricardo

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