arm64: Always keep DAIF.[IF] in sync

Apple SoCs (A11 and newer) have some interrupt sources hardwired to the
FIQ line. We implement support for this by simply treating IRQs and FIQs
the same way in the interrupt vectors.

To support these systems, the FIQ mask bit needs to be kept in sync with
the IRQ mask bit, so both kinds of exceptions are masked together. No
other platforms should be delivering FIQ exceptions right now, and we
already unmask FIQ in normal process context, so this should not have an
effect on other systems - if spurious FIQs were arriving, they would
already panic the kernel.

Signed-off-by: Hector Martin <marcan@marcan.st>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Hector Martin <marcan@marcan.st>
Cc: James Morse <james.morse@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210315115629.57191-6-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 7 insertions, 9 deletions

diff --git a/arch/arm64/include/asm/irqflags.h b/arch/arm64/include/asm/irqflags.h
index ff328e5bbb75..b57b9b1e4344 100644
--- a/arch/arm64/include/asm/irqflags.h
+++ b/arch/arm64/include/asm/irqflags.h
@@ -12,15 +12,13 @@
 
 /*
  * Aarch64 has flags for masking: Debug, Asynchronous (serror), Interrupts and
- * FIQ exceptions, in the 'daif' register. We mask and unmask them in 'dai'
+ * FIQ exceptions, in the 'daif' register. We mask and unmask them in 'daif'
  * order:
  * Masking debug exceptions causes all other exceptions to be masked too/
- * Masking SError masks irq, but not debug exceptions. Masking irqs has no
- * side effects for other flags. Keeping to this order makes it easier for
- * entry.S to know which exceptions should be unmasked.
- *
- * FIQ is never expected, but we mask it when we disable debug exceptions, and
- * unmask it at all other times.
+ * Masking SError masks IRQ/FIQ, but not debug exceptions. IRQ and FIQ are
+ * always masked and unmasked together, and have no side effects for other
+ * flags. Keeping to this order makes it easier for entry.S to know which
+ * exceptions should be unmasked.
  */
 
 /*
@@ -35,7 +33,7 @@ static inline void arch_local_irq_enable(void)
 	}
 
 	asm volatile(ALTERNATIVE(
-		"msr	daifclr, #2		// arch_local_irq_enable",
+		"msr	daifclr, #3		// arch_local_irq_enable",
 		__msr_s(SYS_ICC_PMR_EL1, "%0"),
 		ARM64_HAS_IRQ_PRIO_MASKING)
 		:
@@ -54,7 +52,7 @@ static inline void arch_local_irq_disable(void)
 	}
 
 	asm volatile(ALTERNATIVE(
-		"msr	daifset, #2		// arch_local_irq_disable",
+		"msr	daifset, #3		// arch_local_irq_disable",
 		__msr_s(SYS_ICC_PMR_EL1, "%0"),
 		ARM64_HAS_IRQ_PRIO_MASKING)
 		: