irqchip/gic-v3: Handle pseudo-NMIs

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@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

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 void gic_deactivate_unhandled(u32 irqnr)
+{
+	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);
+	if (err)
+		gic_deactivate_unhandled(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_unhandled(irqnr);
 		}
 		return;
 	}