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| author | Nicholas Piggin | 2017-06-13 15:05:49 +0200 |
|---|---|---|
| committer | Michael Ellerman | 2017-06-19 11:46:28 +0200 |
| commit | b48bbb82e2b83537c500417d60218ad44446e572 (patch) | |
| tree | 11d3df0baa7c3941c188448046b3e51c7db7f578 /arch/powerpc/kernel | |
| parent | powerpc/64s: msgclr when handling doorbell exceptions from system reset (diff) | |
| download | kernel-qcow2-linux-b48bbb82e2b83537c500417d60218ad44446e572.tar.gz kernel-qcow2-linux-b48bbb82e2b83537c500417d60218ad44446e572.tar.xz kernel-qcow2-linux-b48bbb82e2b83537c500417d60218ad44446e572.zip | |
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 <ego@linux.vnet.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/kernel')
| -rw-r--r-- | arch/powerpc/kernel/exceptions-64s.S | 8 |
1 files changed, 7 insertions, 1 deletions
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 + |