irqchip/gic-v3: Switch to PMR masking before calling IRQ handler

Mask the IRQ priority through PMR and re-enable IRQs at CPU level,
allowing only higher priority interrupts to be received during interrupt
handling.
Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Will Deacon <will.deacon@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>

arch/arm/include/asm/arch_gicv3.h

@@ -363,5 +363,22 @@ static inline void gits_write_vpendbaser(u64 val, void * __iomem addr)
 
 #define gits_read_vpendbaser(c)		__gic_readq_nonatomic(c)
 
+static inline bool gic_prio_masking_enabled(void)
+{
+	return false;
+}
+
+static inline void gic_pmr_mask_irqs(void)
+{
+	/* Should not get called. */
+	WARN_ON_ONCE(true);
+}
+
+static inline void gic_arch_enable_irqs(void)
+{
+	/* Should not get called. */
+	WARN_ON_ONCE(true);
+}
+
 #endif /* !__ASSEMBLY__ */
 #endif /* !__ASM_ARCH_GICV3_H */

arch/arm64/include/asm/arch_gicv3.h

@@ -155,5 +155,22 @@ static inline u32 gic_read_rpr(void)
 #define gits_write_vpendbaser(v, c)	writeq_relaxed(v, c)
 #define gits_read_vpendbaser(c)		readq_relaxed(c)
 
+static inline bool gic_prio_masking_enabled(void)
+{
+	return system_uses_irq_prio_masking();
+}
+
+static inline void gic_pmr_mask_irqs(void)
+{
+	/* Should not get called yet. */
+	WARN_ON_ONCE(true);
+}
+
+static inline void gic_arch_enable_irqs(void)
+{
+	/* Should not get called yet. */
+	WARN_ON_ONCE(true);
+}
+
 #endif /* __ASSEMBLY__ */
 #endif /* __ASM_ARCH_GICV3_H */

drivers/irqchip/irq-gic-v3.c

@@ -356,6 +356,11 @@ static asmlinkage void __exception_irq_entry gic_handle_irq(struct pt_regs *regs
 
 	irqnr = gic_read_iar();
 
+	if (gic_prio_masking_enabled()) {
+		gic_pmr_mask_irqs();
+		gic_arch_enable_irqs();
+	}
+
 	if (likely(irqnr > 15 && irqnr < 1020) || irqnr >= 8192) {
 		int err;