From: Anton Blanchard Date: Wed, 4 Apr 2012 18:24:29 +0000 (+0000) Subject: powerpc: No need to save XER in a system call X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=823df43552da39fd48a2dd74949363a1c8cf62bb;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git 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 Signed-off-by: Benjamin Herrenschmidt --- 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)