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>

7 files changed, 41 insertions, 28 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
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 805e20657868..e513c1d35b2a 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -43,7 +43,7 @@ __start_interrupts:
 _machine_check_pSeries:
         HMT_MEDIUM
         DO_KVM  0x200
-        mtspr   SPRN_SPRG_SCRATCH0,r13          /* save r13 */
+        SET_SCRATCH0(r13)
         EXCEPTION_PROLOG_PSERIES(PACA_EXMC, machine_check_common, EXC_STD)
 
         . = 0x300
@@ -51,7 +51,7 @@ _machine_check_pSeries:
 data_access_pSeries:
         HMT_MEDIUM
         DO_KVM  0x300
-        mtspr   SPRN_SPRG_SCRATCH0,r13
+        SET_SCRATCH0(r13)
 BEGIN_FTR_SECTION
         GET_PACA(r13)
         std     r9,PACA_EXSLB+EX_R9(r13)
@@ -67,7 +67,7 @@ BEGIN_FTR_SECTION
         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
+        GET_SCRATCH0(r12)
         std     r10,PACA_EXGEN+EX_R10(r13)
         std     r11,PACA_EXGEN+EX_R9(r13)
         std     r12,PACA_EXGEN+EX_R13(r13)
@@ -81,7 +81,7 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_SLB)
 data_access_slb_pSeries:
         HMT_MEDIUM
         DO_KVM  0x380
-        mtspr   SPRN_SPRG_SCRATCH0,r13
+        SET_SCRATCH0(r13)
         GET_PACA(r13)
         std     r3,PACA_EXSLB+EX_R3(r13)
         mfspr   r3,SPRN_DAR
@@ -95,7 +95,7 @@ data_access_slb_pSeries:
         std     r10,PACA_EXSLB+EX_R10(r13)
         std     r11,PACA_EXSLB+EX_R11(r13)
         std     r12,PACA_EXSLB+EX_R12(r13)
-        mfspr   r10,SPRN_SPRG_SCRATCH0
+        GET_SCRATCH0(r10)
         std     r10,PACA_EXSLB+EX_R13(r13)
         mfspr   r12,SPRN_SRR1           /* and SRR1 */
 #ifndef CONFIG_RELOCATABLE
@@ -120,7 +120,7 @@ data_access_slb_pSeries:
 instruction_access_slb_pSeries:
         HMT_MEDIUM
         DO_KVM  0x480
-        mtspr   SPRN_SPRG_SCRATCH0,r13
+        SET_SCRATCH0(r13)
         GET_PACA(r13)
         std     r3,PACA_EXSLB+EX_R3(r13)
         mfspr   r3,SPRN_SRR0            /* SRR0 is faulting address */
@@ -134,7 +134,7 @@ instruction_access_slb_pSeries:
         std     r10,PACA_EXSLB+EX_R10(r13)
         std     r11,PACA_EXSLB+EX_R11(r13)
         std     r12,PACA_EXSLB+EX_R12(r13)
-        mfspr   r10,SPRN_SPRG_SCRATCH0
+        GET_SCRATCH0(r10)
         std     r10,PACA_EXSLB+EX_R13(r13)
         mfspr   r12,SPRN_SRR1           /* and SRR1 */
 #ifndef CONFIG_RELOCATABLE
@@ -272,7 +272,7 @@ masked_interrupt:
         rotldi  r10,r10,16
         mtspr   SPRN_SRR1,r10
         ld      r10,PACA_EXGEN+EX_R10(r13)
-        mfspr   r13,SPRN_SPRG_SCRATCH0
+        GET_SCRATCH0(r13)
         rfid
         b       .
 
@@ -285,7 +285,7 @@ masked_Hinterrupt:
         rotldi  r10,r10,16
         mtspr   SPRN_HSRR1,r10
         ld      r10,PACA_EXGEN+EX_R10(r13)
-        mfspr   r13,SPRN_SPRG_HSCRATCH0
+        GET_SCRATCH0(r13)
         hrfid
         b       .
 
@@ -293,7 +293,7 @@ masked_Hinterrupt:
 do_stab_bolted_pSeries:
         std     r11,PACA_EXSLB+EX_R11(r13)
         std     r12,PACA_EXSLB+EX_R12(r13)
-        mfspr   r10,SPRN_SPRG_SCRATCH0
+        GET_SCRATCH0(r10)
         std     r10,PACA_EXSLB+EX_R13(r13)
         EXCEPTION_PROLOG_PSERIES_1(.do_stab_bolted, EXC_STD)
 
@@ -305,14 +305,14 @@ do_stab_bolted_pSeries:
       .align 7
 system_reset_fwnmi:
         HMT_MEDIUM
-        mtspr   SPRN_SPRG_SCRATCH0,r13          /* save r13 */
+        SET_SCRATCH0(r13)               /* save r13 */
         EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, system_reset_common, EXC_STD)
 
         .globl machine_check_fwnmi
       .align 7
 machine_check_fwnmi:
         HMT_MEDIUM
-        mtspr   SPRN_SPRG_SCRATCH0,r13          /* save r13 */
+        SET_SCRATCH0(r13)               /* save r13 */
         EXCEPTION_PROLOG_PSERIES(PACA_EXMC, machine_check_common, EXC_STD)
 
 #endif /* CONFIG_PPC_PSERIES */
@@ -327,7 +327,7 @@ slb_miss_user_pseries:
         std     r10,PACA_EXGEN+EX_R10(r13)
         std     r11,PACA_EXGEN+EX_R11(r13)
         std     r12,PACA_EXGEN+EX_R12(r13)
-        mfspr   r10,SPRG_SCRATCH0
+        GET_SCRATCH0(r10)
         ld      r11,PACA_EXSLB+EX_R9(r13)
         ld      r12,PACA_EXSLB+EX_R3(r13)
         std     r10,PACA_EXGEN+EX_R13(r13)
diff --git a/arch/powerpc/kvm/book3s_rmhandlers.S b/arch/powerpc/kvm/book3s_rmhandlers.S
index 046e1f3d4432..ae99af66ca34 100644
--- a/arch/powerpc/kvm/book3s_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_rmhandlers.S
@@ -70,7 +70,7 @@
 .global kvmppc_trampoline_\intno
 kvmppc_trampoline_\intno:
 
-        mtspr   SPRN_SPRG_SCRATCH0, r13         /* Save r13 */
+        SET_SCRATCH0(r13)               /* Save r13 */
 
         /*
          * First thing to do is to find out if we're coming
@@ -89,7 +89,7 @@ kvmppc_trampoline_\intno:
         lwz     r12, (SHADOW_VCPU_OFF + SVCPU_SCRATCH1)(r13)
         mtcr    r12
         PPC_LL  r12, (SHADOW_VCPU_OFF + SVCPU_SCRATCH0)(r13)
-        mfspr   r13, SPRN_SPRG_SCRATCH0         /* r13 = original r13 */
+        GET_SCRATCH0(r13)                       /* r13 = original r13 */
         b       kvmppc_resume_\intno            /* Get back original handler */
 
         /* Now we know we're handling a KVM guest */
@@ -157,7 +157,7 @@ kvmppc_handler_skip_ins:
         lwz     r12, (SHADOW_VCPU_OFF + SVCPU_SCRATCH1)(r13)
         mtcr    r12
         PPC_LL  r12, (SHADOW_VCPU_OFF + SVCPU_SCRATCH0)(r13)
-        mfspr   r13, SPRN_SPRG_SCRATCH0
+        GET_SCRATCH0(r13)
 
         /* And get back into the code */
         RFI
diff --git a/arch/powerpc/kvm/book3s_segment.S b/arch/powerpc/kvm/book3s_segment.S
index d842795d0f23..451264274b8c 100644
--- a/arch/powerpc/kvm/book3s_segment.S
+++ b/arch/powerpc/kvm/book3s_segment.S
@@ -168,7 +168,7 @@ kvmppc_handler_trampoline_exit:
         PPC_STL r4, (SHADOW_VCPU_OFF + SVCPU_SHADOW_SRR1)(r13)
 
         /* Get scratch'ed off registers */
-        mfspr   r9, SPRN_SPRG_SCRATCH0
+        GET_SCRATCH0(r9)
         PPC_LL  r8, (SHADOW_VCPU_OFF + SVCPU_SCRATCH0)(r13)
         lwz     r7, (SHADOW_VCPU_OFF + SVCPU_SCRATCH1)(r13)
 
diff --git a/arch/powerpc/platforms/iseries/exception.S b/arch/powerpc/platforms/iseries/exception.S
index f7a487231a11..32a56c6dfa72 100644
--- a/arch/powerpc/platforms/iseries/exception.S
+++ b/arch/powerpc/platforms/iseries/exception.S
@@ -155,7 +155,7 @@ BEGIN_FTR_SECTION
         std     r12,PACA_EXGEN+EX_R13(r13)
         EXCEPTION_PROLOG_ISERIES_1
 FTR_SECTION_ELSE
-        EXCEPTION_PROLOG_1(PACA_EXGEN, EXC_STD)
+        EXCEPTION_PROLOG_1(PACA_EXGEN)
         EXCEPTION_PROLOG_ISERIES_1
 ALT_FTR_SECTION_END_IFCLR(CPU_FTR_SLB)
         b       data_access_common
diff --git a/arch/powerpc/platforms/iseries/exception.h b/arch/powerpc/platforms/iseries/exception.h
index 57127d805fe3..bae3fba5ad8e 100644
--- a/arch/powerpc/platforms/iseries/exception.h
+++ b/arch/powerpc/platforms/iseries/exception.h
@@ -39,7 +39,7 @@
 label##_iSeries:                                                        \
         HMT_MEDIUM;                                                     \
         mtspr   SPRN_SPRG_SCRATCH0,r13; /* save r13 */                  \
-        EXCEPTION_PROLOG_1(area, EXC_STD);                              \
+        EXCEPTION_PROLOG_1(area);                                       \
         EXCEPTION_PROLOG_ISERIES_1;                                     \
         b       label##_common
 
@@ -48,7 +48,7 @@ label##_iSeries:							\
 label##_iSeries:                                                        \
         HMT_MEDIUM;                                                     \
         mtspr   SPRN_SPRG_SCRATCH0,r13; /* save r13 */                  \
-        EXCEPTION_PROLOG_1(PACA_EXGEN, EXC_STD);                        \
+        EXCEPTION_PROLOG_1(PACA_EXGEN);                                 \
         lbz     r10,PACASOFTIRQEN(r13);                                 \
         cmpwi   0,r10,0;                                                \
         beq-    label##_iSeries_masked;                                 \