linux-kernel - [PATCH v6 20/24] irqchip/gic-v3: Allow interrupts to be set as pseudo-NMI

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Date:   Mon, 12 Nov 2018 11:57:11 +0000
From:   Julien Thierry <julien.thierry@....com>
To:     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,
        Julien Thierry <julien.thierry@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>
Subject: [PATCH v6 20/24] irqchip/gic-v3: Allow interrupts to be set as pseudo-NMI

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 c763f1a..f22ae49 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -27,6 +27,7 @@
 #include <linux/of_address.h>
 #include <linux/of_irq.h>
 #include <linux/percpu.h>
+#include <linux/refcount.h>
 #include <linux/slab.h>
 
 #include <linux/irqchip.h>
@@ -90,6 +91,9 @@ struct gic_chip_data {
  */
 static DEFINE_STATIC_KEY_FALSE(supports_pseudo_nmis);
 
+/* ppi_nmi_refs[n] == number of cpus having ppi[n + 16] set as NMI */
+static refcount_t ppi_nmi_refs[16];
+
 static struct gic_kvm_info gic_v3_kvm_info;
 static DEFINE_PER_CPU(bool, has_rss);
 
@@ -314,6 +318,72 @@ static int gic_irq_get_irqchip_state(struct irq_data *d,
 	return 0;
 }
 
+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);
+}
+
 static void gic_eoi_irq(struct irq_data *d)
 {
 	gic_write_eoir(gic_irq(d));
@@ -950,6 +1020,8 @@ static inline void gic_cpu_pm_init(void) { }
 	.irq_set_affinity	= gic_set_affinity,
 	.irq_get_irqchip_state	= gic_irq_get_irqchip_state,
 	.irq_set_irqchip_state	= gic_irq_set_irqchip_state,
+	.irq_nmi_setup		= gic_irq_nmi_setup,
+	.irq_nmi_teardown	= gic_irq_nmi_teardown,
 	.flags			= IRQCHIP_SET_TYPE_MASKED |
 				  IRQCHIP_SKIP_SET_WAKE |
 				  IRQCHIP_MASK_ON_SUSPEND,
@@ -965,6 +1037,8 @@ static inline void gic_cpu_pm_init(void) { }
 	.irq_get_irqchip_state	= gic_irq_get_irqchip_state,
 	.irq_set_irqchip_state	= gic_irq_set_irqchip_state,
 	.irq_set_vcpu_affinity	= gic_irq_set_vcpu_affinity,
+	.irq_nmi_setup		= gic_irq_nmi_setup,
+	.irq_nmi_teardown	= gic_irq_nmi_teardown,
 	.flags			= IRQCHIP_SET_TYPE_MASKED |
 				  IRQCHIP_SKIP_SET_WAKE |
 				  IRQCHIP_MASK_ON_SUSPEND,
@@ -1159,7 +1233,17 @@ static int partition_domain_translate(struct irq_domain *d,
 
 static void gic_enable_nmi_support(void)
 {
+	int i;
+
+	for (i = 0; i < 16; i++)
+		refcount_set(&ppi_nmi_refs[i], 0);
+
 	static_branch_enable(&supports_pseudo_nmis);
+
+	if (static_branch_likely(&supports_deactivate_key))
+		gic_eoimode1_chip.flags |= IRQCHIP_SUPPORTS_NMI;
+	else
+		gic_chip.flags |= IRQCHIP_SUPPORTS_NMI;
 }
 
 static int __init gic_init_bases(void __iomem *dist_base,
-- 
1.9.1