From 823df43552da39fd48a2dd74949363a1c8cf62bb Mon Sep 17 00:00:00 2001 From: Anton Blanchard <anton@samba.org> Date: Wed, 4 Apr 2012 18:24:29 +0000 Subject: [PATCH] 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> --- arch/powerpc/kernel/entry_64.S | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index e212c2f57fd8..7f1e6de9a5a9 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) -- 2.30.9