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

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>

diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index 773e380b5fe88b0d1ea7ef38a9892f7fd128ce2a..a98653b262312c6b3ca73b92089e7391e61527c2 100644 (file)
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -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

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index a8179cc99ac4878c1429d8fa2e8668d91b8658d5..d17af2b3d4cefbe154a6bae1c5a62e7ad9da51bc 100644 (file)
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -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

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 4e9640cc0563c0f410ffbee098590a24a57a371b..50f2ad36ed0968d81460803f08752968dc20da9d 100644 (file)
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -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
 /*

diff --git a/arch/powerpc/platforms/iseries/exception.S b/arch/powerpc/platforms/iseries/exception.S
index 2b80759792371b89c9153ee0e4e5e8d5bb94c088..5369653dcf6a97c5ee0af420a1d1451433d5c996 100644 (file)
--- a/arch/powerpc/platforms/iseries/exception.S
+++ b/arch/powerpc/platforms/iseries/exception.S
@@ -128,25 +128,36 @@ 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
-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_ISERIES_1
+FTR_SECTION_ELSE
        EXCEPTION_PROLOG_1(PACA_EXGEN)
        EXCEPTION_PROLOG_ISERIES_1
+ALT_FTR_SECTION_END_IFCLR(CPU_FTR_SLB)
        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