powerpc: Add code to handle soft-disabled doorbells on server

This patch adds the logic to properly handle doorbells that come in when
interrupts have been soft disabled and to replay them when interrupts
are re-enabled:

- masked_##_H##interrupt is modified to leave interrupts enabled when a
  doorbell has come in since doorbells are edge sensitive and as such
  won't be automatically re-raised.

- __check_irq_replay now tests if a doorbell happened on book3s, and
  returns either 0xe80 or 0xa00 depending on whether we are the
  hypervisor or not.

- restore_check_irq_replay now tests for the two possible server
  doorbell vector numbers to replay.

- __replay_interrupt also adds tests for the two server doorbell vector
  numbers, and is modified to use a compare instruction rather than an
  andi. on the single bit difference between 0x500 and 0x900.

The last two use a CPU feature section to avoid needlessly testing
against the hypervisor vector if it is not the hypervisor, and vice
versa.

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 9 insertions, 2 deletions

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 71413f41278f..4f97fe345526 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -122,8 +122,8 @@ static inline notrace int decrementer_check_overflow(void)
 }
 
 /* This is called whenever we are re-enabling interrupts
- * and returns either 0 (nothing to do) or 500/900 if there's
- * either an EE or a DEC to generate.
+ * and returns either 0 (nothing to do) or 500/900/280/a00/e80 if
+ * there's an EE, DEC or DBELL to generate.
  *
  * This is called in two contexts: From arch_local_irq_restore()
  * before soft-enabling interrupts, and from the exception exit
@@ -182,6 +182,13 @@ notrace unsigned int __check_irq_replay(void)
         local_paca->irq_happened &= ~PACA_IRQ_DBELL;
         if (happened & PACA_IRQ_DBELL)
                 return 0x280;
+#else
+        local_paca->irq_happened &= ~PACA_IRQ_DBELL;
+        if (happened & PACA_IRQ_DBELL) {
+                if (cpu_has_feature(CPU_FTR_HVMODE))
+                        return 0xe80;
+                return 0xa00;
+        }
 #endif /* CONFIG_PPC_BOOK3E */
 
         /* There should be nothing left ! */