powerpc/64: Change soft_enabled from flag to bitmask

"paca->soft_enabled" is used as a flag to mask some of interrupts.
Currently supported flags values and their details:

soft_enabled    MSR[EE]

0               0       Disabled (PMI and HMI not masked)
1               1       Enabled

"paca->soft_enabled" is initialized to 1 to make the interripts as
enabled. arch_local_irq_disable() will toggle the value when
interrupts needs to disbled. At this point, the interrupts are not
actually disabled, instead, interrupt vector has code to check for the
flag and mask it when it occurs. By "mask it", it update interrupt
paca->irq_happened and return. arch_local_irq_restore() is called to
re-enable interrupts, which checks and replays interrupts if any
occured.

Now, as mentioned, current logic doesnot mask "performance monitoring
interrupts" and PMIs are implemented as NMI. But this patchset depends
on local_irq_* for a successful local_* update. Meaning, mask all
possible interrupts during local_* update and replay them after the
update.

So the idea here is to reserve the "paca->soft_enabled" logic. New
values and details:

soft_enabled    MSR[EE]

1               0       Disabled  (PMI and HMI not masked)
0               1       Enabled

Reason for the this change is to create foundation for a third mask
value "0x2" for "soft_enabled" to add support to mask PMIs. When
->soft_enabled is set to a value "3", PMI interrupts are mask and when
set to a value of "1", PMI are not mask. With this patch also extends
soft_enabled as interrupt disable mask.

Current flags are renamed from IRQ_[EN?DIS}ABLED to
IRQS_ENABLED and IRQS_DISABLED.

Patch also fixes the ptrace call to force the user to see the softe
value to be alway 1. Reason being, even though userspace has no
business knowing about softe, it is part of pt_regs. Like-wise in
signal context.

Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 17 insertions, 3 deletions

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 6c04e465caf5..406c4329b535 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -219,15 +219,29 @@ notrace unsigned int __check_irq_replay(void)
 	return 0;
 }
 
-notrace void arch_local_irq_restore(unsigned long en)
+notrace void arch_local_irq_restore(unsigned long mask)
 {
 	unsigned char irq_happened;
 	unsigned int replay;
 
 	/* Write the new soft-enabled value */
-	soft_enabled_set(en);
-	if (en == IRQS_DISABLED)
+	soft_enabled_set(mask);
+	if (mask) {
+#ifdef CONFIG_TRACE_IRQFLAGS
+		/*
+		 * mask must always include LINUX bit if any
+		 * are set, and interrupts don't get replayed until
+		 * the Linux interrupt is unmasked. This could be
+		 * changed to replay partial unmasks in future,
+		 * which would allow Linux masks to nest inside
+		 * other masks, among other things. For now, be very
+		 * dumb and simple.
+		 */
+		WARN_ON(!(mask & IRQS_DISABLED));
+#endif
 		return;
+	}
+
 	/*
 	 * From this point onward, we can take interrupts, preempt,
 	 * etc... unless we got hard-disabled. We check if an event