powerpc: Always use SPRN_SPRG_HSCRATCH0 when running in HV mode

This uses feature sections to arrange that we always use HSPRG1
as the scratch register in the interrupt entry code rather than
SPRG2 when we're running in hypervisor mode on POWER7.  This will
ensure that we don't trash the guest's SPRG2 when we are running
KVM guests.  To simplify the code, we define GET_SCRATCH0() and
SET_SCRATCH0() macros like the GET_PACA/SET_PACA macros.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

2 files changed, 21 insertions, 8 deletions

diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index fb5b0af30fcf..d6b4849df9b1 100644
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -60,16 +60,15 @@
 #define EXC_HV  H
 #define EXC_STD
 
-#define __EXCEPTION_PROLOG_1(area, h)                                   \
+#define EXCEPTION_PROLOG_1(area)                                        \
         GET_PACA(r13);                                                  \
         std     r9,area+EX_R9(r13);     /* save r9 - r12 */             \
         std     r10,area+EX_R10(r13);                                   \
         std     r11,area+EX_R11(r13);                                   \
         std     r12,area+EX_R12(r13);                                   \
-        mfspr   r9,SPRN_SPRG_##h##SCRATCH0;                             \
+        GET_SCRATCH0(r9);                                               \
         std     r9,area+EX_R13(r13);                                    \
         mfcr    r9
-#define EXCEPTION_PROLOG_1(area, h) __EXCEPTION_PROLOG_1(area, h)
 
 #define __EXCEPTION_PROLOG_PSERIES_1(label, h)                          \
         ld      r12,PACAKBASE(r13);     /* get high part of &label */   \
@@ -85,7 +84,7 @@
         __EXCEPTION_PROLOG_PSERIES_1(label, h)
 
 #define EXCEPTION_PROLOG_PSERIES(area, label, h)                        \
-        EXCEPTION_PROLOG_1(area, h);                                    \
+        EXCEPTION_PROLOG_1(area);                                       \
         EXCEPTION_PROLOG_PSERIES_1(label, h);
 
 /*
@@ -156,7 +155,7 @@
 label##_pSeries:                                        \
         HMT_MEDIUM;                                     \
         DO_KVM  vec;                                    \
-        mtspr   SPRN_SPRG_SCRATCH0,r13;         /* save r13 */  \
+        SET_SCRATCH0(r13);              /* save r13 */          \
         EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, label##_common, EXC_STD)
 
 #define STD_EXCEPTION_HV(loc, vec, label)               \
@@ -165,13 +164,13 @@ label##_pSeries:					\
 label##_hv:                                             \
         HMT_MEDIUM;                                     \
         DO_KVM  vec;                                    \
-        mtspr   SPRN_SPRG_HSCRATCH0,r13;/* save r13 */  \
+        SET_SCRATCH0(r13);      /* save r13 */          \
         EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, label##_common, EXC_HV)
 
 #define __MASKABLE_EXCEPTION_PSERIES(vec, label, h)                     \
         HMT_MEDIUM;                                                     \
         DO_KVM  vec;                                                    \
-        mtspr   SPRN_SPRG_##h##SCRATCH0,r13;    /* save r13 */          \
+        SET_SCRATCH0(r13);    /* save r13 */                            \
         GET_PACA(r13);                                                  \
         std     r9,PACA_EXGEN+EX_R9(r13);       /* save r9, r10 */      \
         std     r10,PACA_EXGEN+EX_R10(r13);                             \
@@ -179,7 +178,7 @@ label##_hv:						\
         mfcr    r9;                                                     \
         cmpwi   r10,0;                                                  \
         beq     masked_##h##interrupt;                                  \
-        mfspr   r10,SPRN_SPRG_##h##SCRATCH0;                            \
+        GET_SCRATCH0(r10);                                              \
         std     r10,PACA_EXGEN+EX_R13(r13);                             \
         std     r11,PACA_EXGEN+EX_R11(r13);                             \
         std     r12,PACA_EXGEN+EX_R12(r13);                             \
diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 13429a0eba09..76d7d5fea5be 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -802,6 +802,20 @@
         FTR_SECTION_ELSE_NESTED(66);                    \
         mtspr   SPRN_SPRG_HPACA,rX;                     \
         ALT_FTR_SECTION_END_NESTED_IFCLR(CPU_FTR_HVMODE_206, 66)
+
+#define GET_SCRATCH0(rX)                                \
+        BEGIN_FTR_SECTION_NESTED(66);                   \
+        mfspr   rX,SPRN_SPRG_SCRATCH0;                  \
+        FTR_SECTION_ELSE_NESTED(66);                    \
+        mfspr   rX,SPRN_SPRG_HSCRATCH0;                 \
+        ALT_FTR_SECTION_END_NESTED_IFCLR(CPU_FTR_HVMODE_206, 66)
+
+#define SET_SCRATCH0(rX)                                \
+        BEGIN_FTR_SECTION_NESTED(66);                   \
+        mtspr   SPRN_SPRG_SCRATCH0,rX;                  \
+        FTR_SECTION_ELSE_NESTED(66);                    \
+        mtspr   SPRN_SPRG_HSCRATCH0,rX;                 \
+        ALT_FTR_SECTION_END_NESTED_IFCLR(CPU_FTR_HVMODE_206, 66)
 #endif
 
 #ifdef CONFIG_PPC_BOOK3E_64