powerpc/booke64: Use SPRG7 for VDSO

Previously SPRG3 was marked for use by both VDSO and critical
interrupts (though critical interrupts were not fully implemented).

In commit 8b64a9dfb091f1eca8b7e58da82f1e7d1d5fe0ad ("powerpc/booke64:
Use SPRG0/3 scratch for bolted TLB miss & crit int"), Mihai Caraman
made an attempt to resolve this conflict by restoring the VDSO value
early in the critical interrupt, but this has some issues:

 - It's incompatible with EXCEPTION_COMMON which restores r13 from the
   by-then-overwritten scratch (this cost me some debugging time).
 - It forces critical exceptions to be a special case handled
   differently from even machine check and debug level exceptions.
 - It didn't occur to me that it was possible to make this work at all
   (by doing a final "ld r13, PACA_EXCRIT+EX_R13(r13)") until after
   I made (most of) this patch. :-)

It might be worth investigating using a load rather than SPRG on return
from all exceptions (except TLB misses where the scratch never leaves
the SPRG) -- it could save a few cycles.  Until then, let's stick with
SPRG for all exceptions.

Since we cannot use SPRG4-7 for scratch without corrupting the state of
a KVM guest, move VDSO to SPRG7 on book3e.  Since neither SPRG4-7 nor
critical interrupts exist on book3s, SPRG3 is still used for VDSO
there.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Cc: Mihai Caraman <mihai.caraman@freescale.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: kvm-ppc@vger.kernel.org

5 files changed, 9 insertions, 24 deletions

diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index b5aacf72ae6f..dba8140ebc20 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -253,7 +253,7 @@ int main(void)
         DEFINE(PACA_SYSTEM_TIME, offsetof(struct paca_struct, system_time));
         DEFINE(PACA_TRAP_SAVE, offsetof(struct paca_struct, trap_save));
         DEFINE(PACA_NAPSTATELOST, offsetof(struct paca_struct, nap_state_lost));
-        DEFINE(PACA_SPRG3, offsetof(struct paca_struct, sprg3));
+        DEFINE(PACA_SPRG_VDSO, offsetof(struct paca_struct, sprg_vdso));
 #endif /* CONFIG_PPC64 */
 
         /* RTAS */
diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
index 41380a424108..89e1133b0185 100644
--- a/arch/powerpc/kernel/exceptions-64e.S
+++ b/arch/powerpc/kernel/exceptions-64e.S
@@ -55,7 +55,6 @@
         mfspr   r13,SPRN_SPRG_PACA;     /* get PACA */                      \
         std     r10,PACA_EX##type+EX_R10(r13);                              \
         std     r11,PACA_EX##type+EX_R11(r13);                              \
-        PROLOG_STORE_RESTORE_SCRATCH_##type;                                \
         mfcr    r10;                    /* save CR */                       \
         mfspr   r11,SPRN_##type##_SRR1;/* what are we coming from */        \
         DO_KVM  intnum,SPRN_##type##_SRR1;    /* KVM hook */                \
@@ -116,20 +115,6 @@
 #define GDBELL_EXCEPTION_PROLOG(n, intnum, addition)                        \
         EXCEPTION_PROLOG(n, intnum, GDBELL, addition##_GDBELL(n))
 
-/*
- * Store user-visible scratch in PACA exception slots and restore proper value
- */
-#define PROLOG_STORE_RESTORE_SCRATCH_GEN
-#define PROLOG_STORE_RESTORE_SCRATCH_GDBELL
-#define PROLOG_STORE_RESTORE_SCRATCH_DBG
-#define PROLOG_STORE_RESTORE_SCRATCH_MC
-
-#define PROLOG_STORE_RESTORE_SCRATCH_CRIT                                   \
-        mfspr   r10,SPRN_SPRG_CRIT_SCRATCH;     /* get r13 */               \
-        std     r10,PACA_EXCRIT+EX_R13(r13);                                \
-        ld      r11,PACA_SPRG3(r13);                                        \
-        mtspr   SPRN_SPRG_CRIT_SCRATCH,r11;
-
 /* Variants of the "addition" argument for the prolog
  */
 #define PROLOG_ADDITION_NONE_GEN(n)
@@ -529,7 +514,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
         mtcr    r10
         ld      r10,PACA_EXCRIT+EX_R10(r13)     /* restore registers */
         ld      r11,PACA_EXCRIT+EX_R11(r13)
-        ld      r13,PACA_EXCRIT+EX_R13(r13)
+        mfspr   r13,SPRN_SPRG_CRIT_SCRATCH
         rfci
 
         /* Normal debug exception */
@@ -542,7 +527,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
         /* Now we mash up things to make it look like we are coming on a
          * normal exception
          */
-        ld      r15,PACA_EXCRIT+EX_R13(r13)
+        mfspr   r15,SPRN_SPRG_CRIT_SCRATCH
         mtspr   SPRN_SPRG_GEN_SCRATCH,r15
         mfspr   r14,SPRN_DBSR
         EXCEPTION_COMMON(0xd00, PACA_EXCRIT, INTS_DISABLE)
diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
index 094e45c16a17..ce74c335a6a4 100644
--- a/arch/powerpc/kernel/vdso.c
+++ b/arch/powerpc/kernel/vdso.c
@@ -715,8 +715,8 @@ int vdso_getcpu_init(void)
         unsigned long cpu, node, val;
 
         /*
-         * SPRG3 contains the CPU in the bottom 16 bits and the NUMA node in
-         * the next 16 bits. The VDSO uses this to implement getcpu().
+         * SPRG_VDSO contains the CPU in the bottom 16 bits and the NUMA node
+         * in the next 16 bits.  The VDSO uses this to implement getcpu().
          */
         cpu = get_cpu();
         WARN_ON_ONCE(cpu > 0xffff);
@@ -725,8 +725,8 @@ int vdso_getcpu_init(void)
         WARN_ON_ONCE(node > 0xffff);
 
         val = (cpu & 0xfff) | ((node & 0xffff) << 16);
-        mtspr(SPRN_SPRG3, val);
-        get_paca()->sprg3 = val;
+        mtspr(SPRN_SPRG_VDSO_WRITE, val);
+        get_paca()->sprg_vdso = val;
 
         put_cpu();
 
diff --git a/arch/powerpc/kernel/vdso32/getcpu.S b/arch/powerpc/kernel/vdso32/getcpu.S
index 47afd08c90f7..23eb9a9441bd 100644
--- a/arch/powerpc/kernel/vdso32/getcpu.S
+++ b/arch/powerpc/kernel/vdso32/getcpu.S
@@ -29,7 +29,7 @@
  */
 V_FUNCTION_BEGIN(__kernel_getcpu)
   .cfi_startproc
-        mfspr   r5,SPRN_USPRG3
+        mfspr   r5,SPRN_SPRG_VDSO_READ
         cmpdi   cr0,r3,0
         cmpdi   cr1,r4,0
         clrlwi  r6,r5,16
diff --git a/arch/powerpc/kernel/vdso64/getcpu.S b/arch/powerpc/kernel/vdso64/getcpu.S
index 47afd08c90f7..23eb9a9441bd 100644
--- a/arch/powerpc/kernel/vdso64/getcpu.S
+++ b/arch/powerpc/kernel/vdso64/getcpu.S
@@ -29,7 +29,7 @@
  */
 V_FUNCTION_BEGIN(__kernel_getcpu)
   .cfi_startproc
-        mfspr   r5,SPRN_USPRG3
+        mfspr   r5,SPRN_SPRG_VDSO_READ
         cmpdi   cr0,r3,0
         cmpdi   cr1,r4,0
         clrlwi  r6,r5,16