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authorAnton Blanchard <anton@samba.org>2012-04-05 05:44:48 +0200
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2012-04-30 07:37:14 +0200
commitfd6c40f3b00a1e76d6a920cb6591907c53450afc (patch)
treed642ee27a10ca9914a56e10b8990c45087a515b7 /arch/powerpc/kernel/entry_64.S
parentpowerpc: No need to preserve count register across system call (diff)
downloadlinux-fd6c40f3b00a1e76d6a920cb6591907c53450afc.tar.xz
linux-fd6c40f3b00a1e76d6a920cb6591907c53450afc.zip
powerpc: Better scheduling of CR save code in system call path
At the moment system call entry looks like: crclr so ... mfcr r9 ... std r9,_CCR(r1) commit bd19c8994a82 ([POWERPC] system call micro optimisation) put some space between the crclr and mfcr in order to avoid a stall. There is still a stall seen between the mfcr and std. We can avoid the crclr by doing it in a GPR with rlwinm which gives us more room to better schedule the sequence. Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/kernel/entry_64.S')
-rw-r--r--arch/powerpc/kernel/entry_64.S16
1 files changed, 7 insertions, 9 deletions
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index ba72ddbe5238..fd4604674468 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -63,15 +63,9 @@ system_call_common:
std r0,GPR0(r1)
std r10,GPR1(r1)
ACCOUNT_CPU_USER_ENTRY(r10, r11)
- /*
- * This "crclr so" clears CR0.SO, which is the error indication on
- * return from this system call. There must be no cmp instruction
- * between it and the "mfcr r9" below, otherwise if XER.SO is set,
- * CR0.SO will get set, causing all system calls to appear to fail.
- */
- crclr so
std r2,GPR2(r1)
std r3,GPR3(r1)
+ mfcr r2
std r4,GPR4(r1)
std r5,GPR5(r1)
std r6,GPR6(r1)
@@ -85,13 +79,17 @@ system_call_common:
std r11,_XER(r1)
std r11,_CTR(r1)
std r9,GPR13(r1)
- mfcr r9
mflr r10
+ /*
+ * This clears CR0.SO (bit 28), which is the error indication on
+ * return from this system call.
+ */
+ rldimi r2,r11,28,(63-28)
li r11,0xc01
- std r9,_CCR(r1)
std r10,_LINK(r1)
std r11,_TRAP(r1)
std r3,ORIG_GPR3(r1)
+ std r2,_CCR(r1)
ld r2,PACATOC(r13)
addi r9,r1,STACK_FRAME_OVERHEAD
ld r11,exception_marker@toc(r2)