powerpc/booke64: Use SPRG0/3 scratch for bolted TLB miss & crit int

Embedded.Hypervisor category defines GSPRG0..3 physical registers for guests.
Avoid SPRG4-7 usage as scratch in host exception handlers, otherwise guest
SPRG4-7 registers will be clobbered.
For bolted TLB miss exception handlers, which is the version currently
supported by KVM, use SPRN_SPRG_GEN_SCRATCH aka SPRG0 instead of
SPRN_SPRG_TLB_SCRATCH aka SPRG6. Keep using TLB PACA slots to fit in one
64-byte cache line.
For critical exception handlers use SPRG3 instead of SPRG7. Provide a routine
to store and restore user-visible SPRGs. This will be subsequently used
to restore VDSO information in SPRG3. Add EX_R13 to paca slots to free up
SPRG3 and change the critical exception epilog to use it.

Signed-off-by: Mihai Caraman <mihai.caraman@freescale.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 15 insertions, 2 deletions

diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
index 83c20e84a4fb..7476b0ae09fb 100644
--- a/arch/powerpc/kernel/exceptions-64e.S
+++ b/arch/powerpc/kernel/exceptions-64e.S
@@ -42,6 +42,7 @@
         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 */                \
@@ -99,6 +100,18 @@
 #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)
+
 /* Variants of the "addition" argument for the prolog
  */
 #define PROLOG_ADDITION_NONE_GEN(n)
@@ -454,7 +467,7 @@ interrupt_end_book3e:
         mtcr    r10
         ld      r10,PACA_EXCRIT+EX_R10(r13)     /* restore registers */
         ld      r11,PACA_EXCRIT+EX_R11(r13)
-        mfspr   r13,SPRN_SPRG_CRIT_SCRATCH
+        ld      r13,PACA_EXCRIT+EX_R13(r13)
         rfci
 
         /* Normal debug exception */
@@ -467,7 +480,7 @@ interrupt_end_book3e:
         /* Now we mash up things to make it look like we are coming on a
          * normal exception
          */
-        mfspr   r15,SPRN_SPRG_CRIT_SCRATCH
+        ld      r15,PACA_EXCRIT+EX_R13(r13)
         mtspr   SPRN_SPRG_GEN_SCRATCH,r15
         mfspr   r14,SPRN_DBSR
         EXCEPTION_COMMON(0xd00, PACA_EXCRIT, INTS_DISABLE)