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 bd19c8994a
([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>
This commit is contained in:
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@ -63,15 +63,9 @@ system_call_common:
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std r0,GPR0(r1)
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std r10,GPR1(r1)
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ACCOUNT_CPU_USER_ENTRY(r10, r11)
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/*
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* This "crclr so" clears CR0.SO, which is the error indication on
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* return from this system call. There must be no cmp instruction
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* between it and the "mfcr r9" below, otherwise if XER.SO is set,
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* CR0.SO will get set, causing all system calls to appear to fail.
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*/
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crclr so
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std r2,GPR2(r1)
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std r3,GPR3(r1)
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mfcr r2
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std r4,GPR4(r1)
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std r5,GPR5(r1)
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std r6,GPR6(r1)
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@ -85,13 +79,17 @@ system_call_common:
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std r11,_XER(r1)
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std r11,_CTR(r1)
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std r9,GPR13(r1)
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mfcr r9
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mflr r10
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/*
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* This clears CR0.SO (bit 28), which is the error indication on
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* return from this system call.
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*/
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rldimi r2,r11,28,(63-28)
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li r11,0xc01
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std r9,_CCR(r1)
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std r10,_LINK(r1)
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std r11,_TRAP(r1)
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std r3,ORIG_GPR3(r1)
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std r2,_CCR(r1)
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ld r2,PACATOC(r13)
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addi r9,r1,STACK_FRAME_OVERHEAD
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ld r11,exception_marker@toc(r2)
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