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authorAnton Blanchard <anton@samba.org>2012-04-04 18:24:29 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2012-04-30 15:34:44 +1000
commit823df43552da39fd48a2dd74949363a1c8cf62bb (patch)
tree6528a931fade61d09a5a83951906cb6dcbaf33f9 /arch/powerpc
parentd14299dec74a094b0f26b0893eccf8aefdfbd007 (diff)
powerpc: No need to save XER in a system call
The XER is a volatile register so there is no need to save and restore it over a system call - zero it out in the exception stack frame instead. This should fix a 5 cycle stall of the mfxer/std seen on POWER7. Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc')
-rw-r--r--arch/powerpc/kernel/entry_64.S3
1 files changed, 1 insertions, 2 deletions
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index e212c2f57fd..7f1e6de9a5a 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -82,6 +82,7 @@ system_call_common:
std r11,GPR10(r1)
std r11,GPR11(r1)
std r11,GPR12(r1)
+ std r11,_XER(r1)
std r9,GPR13(r1)
mfcr r9
mflr r10
@@ -89,9 +90,7 @@ system_call_common:
std r9,_CCR(r1)
std r10,_LINK(r1)
std r11,_TRAP(r1)
- mfxer r9
mfctr r10
- std r9,_XER(r1)
std r10,_CTR(r1)
std r3,ORIG_GPR3(r1)
ld r2,PACATOC(r13)