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powerpc/64s/exception: avoid SPR RAW scoreboard stall in real mode entry

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Move SPR reads ahead of writes. Real mode entry that is not a KVM
guest is rare these days, but bad practice propagates.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin 2019-06-28 15:33:21 +10:00 committed by Michael Ellerman
parent b0b2a93da4
commit 63d60d0c69
1 changed files with 8 additions and 8 deletions
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16
arch/powerpc/kernel/exceptions-64s.S
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@ -183,19 +183,19 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
.endif
.if \hsrr
mfspr r11,SPRN_HSRR0 /* save HSRR0 */
.else
mfspr r11,SPRN_SRR0 /* save SRR0 */
.endif
LOAD_HANDLER(r12, \label\())
.if \hsrr
mtspr SPRN_HSRR0,r12
mfspr r12,SPRN_HSRR1 /* and HSRR1 */
mtspr SPRN_HSRR1,r10
HRFI_TO_KERNEL
.else
mtspr SPRN_SRR0,r12
mfspr r11,SPRN_SRR0 /* save SRR0 */
mfspr r12,SPRN_SRR1 /* and SRR1 */
mtspr SPRN_SRR1,r10
.endif
LOAD_HANDLER(r10, \label\())
.if \hsrr
mtspr SPRN_HSRR0,r10
HRFI_TO_KERNEL
.else
mtspr SPRN_SRR0,r10
RFI_TO_KERNEL
.endif
b . /* prevent speculative execution */