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powerpc: Remove use of a second scratch SPRG in STAB code

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The STAB code used on Power3 and RS/64 uses a second scratch SPRG to
save a GPR in order to decide whether to go to do_stab_bolted_* or
to handle a normal data access exception.

This prevents our scheme of freeing SPRG3 which is user visible for
user uses since we cannot use SPRG0 which, on RS/64, seems to be
read-only for supervisor mode (like POWER4).

This reworks the STAB exception entry to use the PACA as temporary
storage instead.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Benjamin Herrenschmidt
2009-07-16 19:36:57 +00:00
parent ee43eb788b
commit c5a8c0c99f
4 changed files with 55 additions and 30 deletions
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38
arch/powerpc/kernel/exceptions-64s.S
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@@ -50,18 +50,28 @@ data_access_pSeries:
HMT_MEDIUM
mtspr SPRN_SPRG_SCRATCH0,r13
BEGIN_FTR_SECTION
mtspr SPRN_SPRG_SCRATCH1,r12
mfspr r13,SPRN_DAR
mfspr r12,SPRN_DSISR
srdi r13,r13,60
rlwimi r13,r12,16,0x20
mfcr r12
cmpwi r13,0x2c
mfspr r13,SPRN_SPRG_PACA
std r9,PACA_EXSLB+EX_R9(r13)
std r10,PACA_EXSLB+EX_R10(r13)
mfspr r10,SPRN_DAR
mfspr r9,SPRN_DSISR
srdi r10,r10,60
rlwimi r10,r9,16,0x20
mfcr r9
cmpwi r10,0x2c
beq do_stab_bolted_pSeries
mtcrf 0x80,r12
mfspr r12,SPRN_SPRG_SCRATCH1
END_FTR_SECTION_IFCLR(CPU_FTR_SLB)
ld r10,PACA_EXSLB+EX_R10(r13)
std r11,PACA_EXGEN+EX_R11(r13)
ld r11,PACA_EXSLB+EX_R9(r13)
std r12,PACA_EXGEN+EX_R12(r13)
mfspr r12,SPRN_SPRG_SCRATCH0
std r10,PACA_EXGEN+EX_R10(r13)
std r11,PACA_EXGEN+EX_R9(r13)
std r12,PACA_EXGEN+EX_R13(r13)
EXCEPTION_PROLOG_PSERIES_1(data_access_common)
FTR_SECTION_ELSE
EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, data_access_common)
ALT_FTR_SECTION_END_IFCLR(CPU_FTR_SLB)
. = 0x380
.globl data_access_slb_pSeries
@@ -224,9 +234,11 @@ masked_interrupt:
.align 7
do_stab_bolted_pSeries:
mtcrf 0x80,r12
mfspr r12,SPRN_SPRG_SCRATCH1
EXCEPTION_PROLOG_PSERIES(PACA_EXSLB, .do_stab_bolted)
std r11,PACA_EXSLB+EX_R11(r13)
std r12,PACA_EXSLB+EX_R12(r13)
mfspr r10,SPRN_SPRG_SCRATCH0
std r10,PACA_EXSLB+EX_R13(r13)
EXCEPTION_PROLOG_PSERIES_1(.do_stab_bolted)
#ifdef CONFIG_PPC_PSERIES
/*