The __replay_interrupt code is branched to with bl, but the caller is
returned to directly with rfid from the interrupt.
Instead, rfid to a stub that returns to the caller with blr, which
should keep the return branch predictor balanced.
Reviewed-by: Gautham R. Shenoy <e...@linux.vnet.ibm.com>
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
arch/powerpc/kernel/exceptions-64s.S | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/exceptions-64s.S
b/arch/powerpc/kernel/exceptions-64s.S
index a04ee0d7f88e..31a9114860c4 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -1579,6 +1579,10 @@ doorbell_super_common_msgclr:
* Note: While MSR:EE is off, we need to make sure that _MSR
* in the generated frame has EE set to 1 or the exception
* handler will not properly re-enable them.
+ *
+ * Note that we don't specify LR as the NIP (return address) for
+ * the interrupt because that would unbalance the return branch
+ * predictor.
*/
_GLOBAL(__replay_interrupt)
/* We are going to jump to the exception common code which
@@ -1586,7 +1590,7 @@ _GLOBAL(__replay_interrupt)
* we don't give a damn about, so we don't bother storing them.
*/
mfmsr r12
- mflr r11
+ LOAD_REG_ADDR(r11, .L__replay_interrupt_return)
mfcr r9
ori r12,r12,MSR_EE
cmpwi r3,0x900
@@ -1604,4 +1608,6 @@ FTR_SECTION_ELSE
cmpwi r3,0xa00
beq doorbell_super_common_msgclr
ALT_FTR_SECTION_END_IFSET(CPU_FTR_HVMODE)
+.L__replay_interrupt_return:
blr
+
--
2.11.0
