linux-kernel - Re: [PATCH v9 22/26] irqchip/gic-v3: Allow interrupts to be set as pseudo-NMI

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Date:   Sat, 26 Jan 2019 18:19:52 +0800
From:   "liwei (GF)" <liwei391@...wei.com>
To:     Julien Thierry <julien.thierry@....com>,
        <linux-arm-kernel@...ts.infradead.org>
CC:     <linux-kernel@...r.kernel.org>, <daniel.thompson@...aro.org>,
        <joel@...lfernandes.org>, <marc.zyngier@....com>,
        <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 22/26] irqchip/gic-v3: Allow interrupts to be set as
 pseudo-NMI



On 2019/1/21 23:33, Julien Thierry wrote:
> Implement NMI callbacks for GICv3 irqchip. Install NMI safe handlers
> when setting up interrupt line as NMI.
> 
> Only SPIs and PPIs are allowed to be set up as NMI.
> 
> 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 | 84 ++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 84 insertions(+)
> 
> diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
> index 4df1e94..447d8ab 100644
> --- a/drivers/irqchip/irq-gic-v3.c
> +++ b/drivers/irqchip/irq-gic-v3.c
(snip)
>  
> +static int gic_irq_nmi_setup(struct irq_data *d)
> +{
> +	struct irq_desc *desc = irq_to_desc(d->irq);
> +
> +	if (!gic_supports_nmi())
> +		return -EINVAL;
> +
> +	if (gic_peek_irq(d, GICD_ISENABLER)) {
> +		pr_err("Cannot set NMI property of enabled IRQ %u\n", d->irq);
> +		return -EINVAL;
> +	}
> +
> +	/*
> +	 * A secondary irq_chip should be in charge of LPI request,
> +	 * it should not be possible to get there
> +	 */
> +	if (WARN_ON(gic_irq(d) >= 8192))
> +		return -EINVAL;
> +
> +	/* desc lock should already be held */
> +	if (gic_irq(d) < 32) {
> +		/* Setting up PPI as NMI, only switch handler for first NMI */
> +		if (!refcount_inc_not_zero(&ppi_nmi_refs[gic_irq(d) - 16])) {
> +			refcount_set(&ppi_nmi_refs[gic_irq(d) - 16], 1);
> +			desc->handle_irq = handle_percpu_devid_fasteoi_nmi;
> +		}
> +	} else {
> +		desc->handle_irq = handle_fasteoi_nmi;
> +	}
> +
> +	gic_set_irq_prio(gic_irq(d), gic_dist_base(d), GICD_INT_NMI_PRI);
> +
> +	return 0;
> +}
> +
> +static void gic_irq_nmi_teardown(struct irq_data *d)
> +{
> +	struct irq_desc *desc = irq_to_desc(d->irq);
> +
> +	if (WARN_ON(!gic_supports_nmi()))
> +		return;
> +
> +	if (gic_peek_irq(d, GICD_ISENABLER)) {
> +		pr_err("Cannot set NMI property of enabled IRQ %u\n", d->irq);
> +		return;
> +	}
> +
> +	/*
> +	 * A secondary irq_chip should be in charge of LPI request,
> +	 * it should not be possible to get there
> +	 */
> +	if (WARN_ON(gic_irq(d) >= 8192))
> +		return;
> +
> +	/* desc lock should already be held */
> +	if (gic_irq(d) < 32) {
> +		/* Tearing down NMI, only switch handler for last NMI */
> +		if (refcount_dec_and_test(&ppi_nmi_refs[gic_irq(d) - 16]))
> +			desc->handle_irq = handle_percpu_devid_irq;
> +	} else {
> +		desc->handle_irq = handle_fasteoi_irq;
> +	}
> +
> +	gic_set_irq_prio(gic_irq(d), gic_dist_base(d), GICD_INT_DEF_PRI);
> +}
> +

Hello Julien,
I am afraid the setting of priority is not correct here. If the irq is in redistributor(gic_irq(d) < 32),
we should set the priority on each cpu, while we just set the priority on the current cpu here.
static inline void __iomem *gic_dist_base(struct irq_data *d)
{
	if (gic_irq_in_rdist(d))	/* SGI+PPI -> SGI_base for this CPU */
		return gic_data_rdist_sgi_base();

	if (d->hwirq <= 1023)		/* SPI -> dist_base */
		return gic_data.dist_base;

	return NULL;
}

I tried to add a smp_call_function here, but the kernel reported a warning as we have disabled irq
when calling raw_spin_lock_irqsave in request_nmi or ready_percpu_nmi.
[    2.137262] Call trace:
[    2.137265]  smp_call_function_many+0xf8/0x3a0
[    2.137267]  smp_call_function+0x40/0x58
[    2.137271]  gic_irq_nmi_setup+0xe8/0x118
[    2.137275]  ready_percpu_nmi+0x6c/0xf0
[    2.137279]  armpmu_request_irq+0x228/0x250
[    2.137281]  arm_pmu_acpi_init+0x150/0x2f0
[    2.137284]  do_one_initcall+0x54/0x218
[    2.137289]  kernel_init_freeable+0x230/0x354
[    2.137293]  kernel_init+0x18/0x118
[    2.137295]  ret_from_fork+0x10/0x18

I am exploring a better way to solve this issue.

Thanks,
Wei Li