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 <b...@kernel.crashing.org> --- arch/powerpc/include/asm/exception-64s.h | 7 ++++- arch/powerpc/include/asm/reg.h | 3 -- arch/powerpc/kernel/exceptions-64s.S | 36 ++++++++++++++++++----------- arch/powerpc/platforms/iseries/exception.S | 34 ++++++++++++++++----------- 4 files changed, 50 insertions(+), 30 deletions(-) --- linux-work.orig/arch/powerpc/include/asm/exception-64s.h 2009-07-15 15:07:50.000000000 +1000 +++ linux-work/arch/powerpc/include/asm/exception-64s.h 2009-07-15 15:15:36.000000000 +1000 @@ -66,8 +66,7 @@ std r9,area+EX_R13(r13); \ mfcr r9 -#define EXCEPTION_PROLOG_PSERIES(area, label) \ - EXCEPTION_PROLOG_1(area); \ +#define EXCEPTION_PROLOG_PSERIES_1(label) \ ld r12,PACAKBASE(r13); /* get high part of &label */ \ ld r10,PACAKMSR(r13); /* get MSR value for kernel */ \ mfspr r11,SPRN_SRR0; /* save SRR0 */ \ @@ -78,6 +77,10 @@ rfid; \ b . /* prevent speculative execution */ +#define EXCEPTION_PROLOG_PSERIES(area, label) \ + EXCEPTION_PROLOG_1(area); \ + EXCEPTION_PROLOG_PSERIES_1(label); + /* * The common exception prolog is used for all except a few exceptions * such as a segment miss on a kernel address. We have to be prepared Index: linux-work/arch/powerpc/kernel/exceptions-64s.S =================================================================== --- linux-work.orig/arch/powerpc/kernel/exceptions-64s.S 2009-07-15 15:07:50.000000000 +1000 +++ linux-work/arch/powerpc/kernel/exceptions-64s.S 2009-07-15 15:39:12.000000000 +1000 @@ -50,18 +50,26 @@ 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 + 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) END_FTR_SECTION_IFCLR(CPU_FTR_SLB) - EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, data_access_common) + EXCEPTION_PROLOG_PSERIES_1(data_access_common) . = 0x380 .globl data_access_slb_pSeries @@ -224,9 +232,11 @@ 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 /* Index: linux-work/arch/powerpc/platforms/iseries/exception.S =================================================================== --- linux-work.orig/arch/powerpc/platforms/iseries/exception.S 2009-07-15 15:07:50.000000000 +1000 +++ linux-work/arch/powerpc/platforms/iseries/exception.S 2009-07-15 15:39:14.000000000 +1000 @@ -128,25 +128,33 @@ iSeries_secondary_smp_loop: data_access_iSeries: 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_iSeries - mtcrf 0x80,r12 - mfspr r12,SPRN_SPRG_SCRATCH1 + 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) END_FTR_SECTION_IFCLR(CPU_FTR_SLB) - EXCEPTION_PROLOG_1(PACA_EXGEN) EXCEPTION_PROLOG_ISERIES_1 b data_access_common .do_stab_bolted_iSeries: - mtcrf 0x80,r12 - mfspr r12,SPRN_SPRG_SCRATCH1 - EXCEPTION_PROLOG_1(PACA_EXSLB) + 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_ISERIES_1 b .do_stab_bolted Index: linux-work/arch/powerpc/include/asm/reg.h =================================================================== --- linux-work.orig/arch/powerpc/include/asm/reg.h 2009-07-15 15:23:52.000000000 +1000 +++ linux-work/arch/powerpc/include/asm/reg.h 2009-07-15 15:24:07.000000000 +1000 @@ -654,7 +654,7 @@ * 64-bit server: * - SPRG0 unused (reserved for HV on Power4) * - SPRG1 scratch for exception vectors - * - SPRG2 scratch for exception vectors + * - SPRG2 unused * * All 32-bit: * - SPRG3 current thread_info pointer @@ -707,7 +707,6 @@ #ifdef CONFIG_PPC_BOOK3S_64 #define SPRN_SPRG_SCRATCH0 SPRN_SPRG1 -#define SPRN_SPRG_SCRATCH1 SPRN_SPRG2 #endif #ifdef CONFIG_PPC_BOOK3S_32 _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev