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

12 files changed, 33 insertions, 47 deletions

diff --git a/arch/powerpc/include/asm/exception-64e.h b/arch/powerpc/include/asm/exception-64e.h
index 51fa43e536b9..e73452f09019 100644
--- a/arch/powerpc/include/asm/exception-64e.h
+++ b/arch/powerpc/include/asm/exception-64e.h
@@ -46,9 +46,8 @@
 #define EX_CR           (1 * 8)
 #define EX_R10          (2 * 8)
 #define EX_R11          (3 * 8)
-#define EX_R13          (4 * 8)
-#define EX_R14          (5 * 8)
-#define EX_R15          (6 * 8)
+#define EX_R14          (4 * 8)
+#define EX_R15          (5 * 8)
 
 /*
  * The TLB miss exception uses different slots.
diff --git a/arch/powerpc/include/asm/kvm_booke_hv_asm.h b/arch/powerpc/include/asm/kvm_booke_hv_asm.h
index 3a79f5325712..c3e3fd53a3a9 100644
--- a/arch/powerpc/include/asm/kvm_booke_hv_asm.h
+++ b/arch/powerpc/include/asm/kvm_booke_hv_asm.h
@@ -36,20 +36,13 @@
  *   *(r8 + GPR11) = saved r11
  *
  * 64-bit host
- * Expected inputs (GEN/GDBELL/DBG/MC exception types):
+ * Expected inputs (GEN/GDBELL/DBG/CRIT/MC exception types):
  *  r10 = saved CR
  *  r13 = PACA_POINTER
  *  *(r13 + PACA_EX##type + EX_R10) = saved r10
  *  *(r13 + PACA_EX##type + EX_R11) = saved r11
  *  SPRN_SPRG_##type##_SCRATCH = saved r13
  *
-  * Expected inputs (CRIT exception type):
- *  r10 = saved CR
- *  r13 = PACA_POINTER
- *  *(r13 + PACA_EX##type + EX_R10) = saved r10
- *  *(r13 + PACA_EX##type + EX_R11) = saved r11
- *  *(r13 + PACA_EX##type + EX_R13) = saved r13
- *
  * Expected inputs (TLB exception type):
  *  r10 = saved CR
  *  r13 = PACA_POINTER
diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index 9c5dbc3833fb..948f01a04cc3 100644
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -146,7 +146,7 @@ struct paca_struct {
         u8 io_sync;                     /* writel() needs spin_unlock sync */
         u8 irq_work_pending;            /* IRQ_WORK interrupt while soft-disable */
         u8 nap_state_lost;              /* NV GPR values lost in power7_idle */
-        u64 sprg3;                      /* Saved user-visible sprg */
+        u64 sprg_vdso;                  /* Saved user-visible sprg */
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
         u64 tm_scratch;                 /* TM scratch area for reclaim */
 #endif
diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index bf0fb4db0855..f7251c2dc049 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -577,9 +577,13 @@
 #define SPRN_SPRG3      0x113   /* Special Purpose Register General 3 */
 #define SPRN_USPRG3     0x103   /* SPRG3 userspace read */
 #define SPRN_SPRG4      0x114   /* Special Purpose Register General 4 */
+#define SPRN_USPRG4     0x104   /* SPRG4 userspace read */
 #define SPRN_SPRG5      0x115   /* Special Purpose Register General 5 */
+#define SPRN_USPRG5     0x105   /* SPRG5 userspace read */
 #define SPRN_SPRG6      0x116   /* Special Purpose Register General 6 */
+#define SPRN_USPRG6     0x106   /* SPRG6 userspace read */
 #define SPRN_SPRG7      0x117   /* Special Purpose Register General 7 */
+#define SPRN_USPRG7     0x107   /* SPRG7 userspace read */
 #define SPRN_SRR0       0x01A   /* Save/Restore Register 0 */
 #define SPRN_SRR1       0x01B   /* Save/Restore Register 1 */
 #define   SRR1_ISI_NOPT         0x40000000 /* ISI: Not found in hash */
@@ -879,11 +883,10 @@
  * 64-bit embedded
  *      - SPRG0 generic exception scratch
  *      - SPRG2 TLB exception stack
- *      - SPRG3 critical exception scratch and
- *        CPU and NUMA node for VDSO getcpu (user visible)
+ *      - SPRG3 critical exception scratch (user visible, sorry!)
  *      - SPRG4 unused (user visible)
  *      - SPRG6 TLB miss scratch (user visible, sorry !)
- *      - SPRG7 critical exception scratch
+ *      - SPRG7 CPU and NUMA node for VDSO getcpu (user visible)
  *      - SPRG8 machine check exception scratch
  *      - SPRG9 debug exception scratch
  *
@@ -940,6 +943,8 @@
 #define SPRN_SPRG_SCRATCH0      SPRN_SPRG2
 #define SPRN_SPRG_HPACA         SPRN_HSPRG0
 #define SPRN_SPRG_HSCRATCH0     SPRN_HSPRG1
+#define SPRN_SPRG_VDSO_READ     SPRN_USPRG3
+#define SPRN_SPRG_VDSO_WRITE    SPRN_SPRG3
 
 #define GET_PACA(rX)                                    \
         BEGIN_FTR_SECTION_NESTED(66);                   \
@@ -983,6 +988,8 @@
 #define SPRN_SPRG_TLB_SCRATCH   SPRN_SPRG6
 #define SPRN_SPRG_GEN_SCRATCH   SPRN_SPRG0
 #define SPRN_SPRG_GDBELL_SCRATCH SPRN_SPRG_GEN_SCRATCH
+#define SPRN_SPRG_VDSO_READ     SPRN_USPRG7
+#define SPRN_SPRG_VDSO_WRITE    SPRN_SPRG7
 
 #define SET_PACA(rX)    mtspr   SPRN_SPRG_PACA,rX
 #define GET_PACA(rX)    mfspr   rX,SPRN_SPRG_PACA
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
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index e66d4ec04d95..fbfca5778b0b 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -75,8 +75,8 @@ BEGIN_FTR_SECTION
 END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_207S)
 
         /* Restore SPRG3 */
-        ld      r3,PACA_SPRG3(r13)
-        mtspr   SPRN_SPRG3,r3
+        ld      r3,PACA_SPRG_VDSO(r13)
+        mtspr   SPRN_SPRG_VDSO_WRITE,r3
 
         /* Reload the host's PMU registers */
         ld      r3, PACALPPACAPTR(r13)  /* is the host using the PMU? */
diff --git a/arch/powerpc/kvm/book3s_interrupts.S b/arch/powerpc/kvm/book3s_interrupts.S
index f779450cb07c..3533c999194a 100644
--- a/arch/powerpc/kvm/book3s_interrupts.S
+++ b/arch/powerpc/kvm/book3s_interrupts.S
@@ -153,8 +153,8 @@ kvm_start_lightweight:
          * Reload kernel SPRG3 value.
          * No need to save guest value as usermode can't modify SPRG3.
          */
-        ld      r3, PACA_SPRG3(r13)
-        mtspr   SPRN_SPRG3, r3
+        ld      r3, PACA_SPRG_VDSO(r13)
+        mtspr   SPRN_SPRG_VDSO_WRITE, r3
 #endif /* CONFIG_PPC_BOOK3S_64 */
 
         /* R7 = vcpu */
diff --git a/arch/powerpc/kvm/bookehv_interrupts.S b/arch/powerpc/kvm/bookehv_interrupts.S
index e4185f6b3309..99635a37c78c 100644
--- a/arch/powerpc/kvm/bookehv_interrupts.S
+++ b/arch/powerpc/kvm/bookehv_interrupts.S
@@ -229,11 +229,7 @@
         stw     r10, VCPU_CR(r4)
         PPC_STL r11, VCPU_GPR(R4)(r4)
         PPC_STL r5, VCPU_GPR(R5)(r4)
-        .if \type == EX_CRIT
-        PPC_LL  r5, (\paca_ex + EX_R13)(r13)
-        .else
         mfspr   r5, \scratch
-        .endif
         PPC_STL r6, VCPU_GPR(R6)(r4)
         PPC_STL r8, VCPU_GPR(R8)(r4)
         PPC_STL r9, VCPU_GPR(R9)(r4)
@@ -435,10 +431,16 @@ _GLOBAL(kvmppc_resume_host)
         PPC_STL r5, VCPU_LR(r4)
         mfspr   r7, SPRN_SPRG5
         stw     r3, VCPU_VRSAVE(r4)
+#ifdef CONFIG_64BIT
+        PPC_LL  r3, PACA_SPRG_VDSO(r13)
+#endif
         PPC_STD(r6, VCPU_SHARED_SPRG4, r11)
         mfspr   r8, SPRN_SPRG6
         PPC_STD(r7, VCPU_SHARED_SPRG5, r11)
         mfspr   r9, SPRN_SPRG7
+#ifdef CONFIG_64BIT
+        mtspr   SPRN_SPRG_VDSO_WRITE, r3
+#endif
         PPC_STD(r8, VCPU_SHARED_SPRG6, r11)
         mfxer   r3
         PPC_STD(r9, VCPU_SHARED_SPRG7, r11)