From b48bbb82e2b83537c500417d60218ad44446e572 Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Tue, 13 Jun 2017 23:05:49 +1000 Subject: powerpc/64s: Don't unbalance the return branch predictor in __replay_interrupt() 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 Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman --- arch/powerpc/kernel/exceptions-64s.S | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'arch/powerpc/kernel') diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S index 1752beefee69..cad3b4b82813 100644 --- a/arch/powerpc/kernel/exceptions-64s.S +++ b/arch/powerpc/kernel/exceptions-64s.S @@ -1639,6 +1639,10 @@ 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 @@ -1646,7 +1650,7 @@ _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 @@ -1664,4 +1668,6 @@ FTR_SECTION_ELSE cmpwi r3,0xa00 beq doorbell_super_common_msgclr ALT_FTR_SECTION_END_IFSET(CPU_FTR_HVMODE) +.L__replay_interrupt_return: blr + -- cgit v1.2.3-55-g7522