[RFC PATCH 8/9] powerpc: Support to replay PMIs

[Madhavan Srinivasan <maddy@linux.vnet.ibm.com>]

Code to replay the Performance Monitoring Interrupts(PMI).
In the masked_interrupt handler, for PMIs we reset the MSR[EE]
and return. This is due the fact that PMIs are level triggered.
In the __check_irq_replay(), we enabled the MSR[EE] which will
fire the interrupt for us.

Patch also adds a new arch_local_irq_disable_var() variant. New
variant takes an input value to write to the paca->soft_enabled.
This will be used in following patch to implement the tri-state
value for soft-enabled.

Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/hw_irq.h | 14 ++++++++++++++
 arch/powerpc/kernel/irq.c         |  9 ++++++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h
index cc69dde6eb84..863179654452 100644
--- a/arch/powerpc/include/asm/hw_irq.h
+++ b/arch/powerpc/include/asm/hw_irq.h
@@ -81,6 +81,20 @@ static inline unsigned long arch_local_irq_disable(void)
 	return flags;
 }
 
+static inline unsigned long arch_local_irq_disable_var(int value)
+{
+	unsigned long flags, zero;
+
+	asm volatile(
+		"li %1,%3; lbz %0,%2(13); stb %1,%2(13)"
+		: "=r" (flags), "=&r" (zero)
+		: "i" (offsetof(struct paca_struct, soft_enabled)),\
+		  "i" (value)
+		: "memory");
+
+	return flags;
+}
+
 extern void arch_local_irq_restore(unsigned long);
 
 static inline void arch_local_irq_enable(void)
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 597c20d1814c..81fe0da1f86d 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -158,9 +158,16 @@ notrace unsigned int __check_irq_replay(void)
 	if ((happened & PACA_IRQ_DEC) || decrementer_check_overflow())
 		return 0x900;
 
+	/*
+	 * In masked_handler() for PMI, we disable MSR[EE] and return.
+	 * When replaying it, just enabling the MSR[EE] will do
+	 * trick, since the PMI are "level" triggered.
+	 */
+	local_paca->irq_happened &= ~PACA_IRQ_PMI;
+
 	/* Finally check if an external interrupt happened */
 	local_paca->irq_happened &= ~PACA_IRQ_EE;
-	if (happened & PACA_IRQ_EE)
+	if ((happened & PACA_IRQ_EE) || (happened & PACA_IRQ_PMI))
 		return 0x500;
 
 #ifdef CONFIG_PPC_BOOK3E
-- 
2.7.4