Re: [PATCH 2/4] genirq: Provide NMI management for percpu_devid interrupts

From: Ricardo Neri
Date: Tue Jul 31 2018 - 23:16:32 EST


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@xxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> 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