[Qemu-devel] [PATCH 47/58] Implement POWER7's CFAR in TCG

[Alexander Graf <agraf@suse.de>]

From: David Gibson <david@gibson.dropbear.id.au>

This patch implements support for the CFAR SPR on POWER7 (Come From
Address Register), which snapshots the PC value at the time of a branch or
an rfid.  The latest powerpc-next kernel also catches it and can show it in
xmon or in the signal frames.

This works well enough to let recent kernels boot (which otherwise oops
on the CFAR access).  It hasn't been tested enough to be confident that the
CFAR values are actually accurate, but one thing at a time.

Signed-off-by: Ben Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>
---
 target-ppc/cpu.h            |    8 ++++++++
 target-ppc/translate.c      |   28 ++++++++++++++++++++++++++++
 target-ppc/translate_init.c |   23 ++++++++++++++++++++++-
 3 files changed, 58 insertions(+), 1 deletions(-)

diff --git a/target-ppc/cpu.h b/target-ppc/cpu.h
index 32706df..3f4af22 100644
--- a/target-ppc/cpu.h
+++ b/target-ppc/cpu.h
@@ -555,6 +555,8 @@ enum {
     /* Decrementer clock: RTC clock (POWER, 601) or bus clock                */
     POWERPC_FLAG_RTC_CLK  = 0x00010000,
     POWERPC_FLAG_BUS_CLK  = 0x00020000,
+    /* Has CFAR                                                              */
+    POWERPC_FLAG_CFAR     = 0x00040000,
 };
 
 /*****************************************************************************/
@@ -872,6 +874,10 @@ struct CPUPPCState {
     target_ulong ctr;
     /* condition register */
     uint32_t crf[8];
+#if defined(TARGET_PPC64)
+    /* CFAR */
+    target_ulong cfar;
+#endif
     /* XER */
     target_ulong xer;
     /* Reservation address */
@@ -1204,6 +1210,7 @@ static inline void cpu_clone_regs(CPUState *env, target_ulong newsp)
 #define SPR_601_UDECR         (0x006)
 #define SPR_LR                (0x008)
 #define SPR_CTR               (0x009)
+#define SPR_DSCR              (0x011)
 #define SPR_DSISR             (0x012)
 #define SPR_DAR               (0x013) /* DAE for PowerPC 601 */
 #define SPR_601_RTCU          (0x014)
@@ -1212,6 +1219,7 @@ static inline void cpu_clone_regs(CPUState *env, target_ulong newsp)
 #define SPR_SDR1              (0x019)
 #define SPR_SRR0              (0x01A)
 #define SPR_SRR1              (0x01B)
+#define SPR_CFAR              (0x01C)
 #define SPR_AMR               (0x01D)
 #define SPR_BOOKE_PID         (0x030)
 #define SPR_BOOKE_DECAR       (0x036)
diff --git a/target-ppc/translate.c b/target-ppc/translate.c
index 4277460..1e362fc 100644
--- a/target-ppc/translate.c
+++ b/target-ppc/translate.c
@@ -69,6 +69,9 @@ static TCGv cpu_nip;
 static TCGv cpu_msr;
 static TCGv cpu_ctr;
 static TCGv cpu_lr;
+#if defined(TARGET_PPC64)
+static TCGv cpu_cfar;
+#endif
 static TCGv cpu_xer;
 static TCGv cpu_reserve;
 static TCGv_i32 cpu_fpscr;
@@ -154,6 +157,11 @@ void ppc_translate_init(void)
     cpu_lr = tcg_global_mem_new(TCG_AREG0,
                                 offsetof(CPUState, lr), "lr");
 
+#if defined(TARGET_PPC64)
+    cpu_cfar = tcg_global_mem_new(TCG_AREG0,
+                                  offsetof(CPUState, cfar), "cfar");
+#endif
+
     cpu_xer = tcg_global_mem_new(TCG_AREG0,
                                  offsetof(CPUState, xer), "xer");
 
@@ -187,6 +195,7 @@ typedef struct DisasContext {
     int le_mode;
 #if defined(TARGET_PPC64)
     int sf_mode;
+    int has_cfar;
 #endif
     int fpu_enabled;
     int altivec_enabled;
@@ -3345,6 +3354,14 @@ static inline void gen_qemu_st32fiw(DisasContext *ctx, TCGv_i64 arg1, TCGv arg2)
 /* stfiwx */
 GEN_STXF(stfiw, st32fiw, 0x17, 0x1E, PPC_FLOAT_STFIWX);
 
+static inline void gen_update_cfar(DisasContext *ctx, target_ulong nip)
+{
+#if defined(TARGET_PPC64)
+    if (ctx->has_cfar)
+        tcg_gen_movi_tl(cpu_cfar, nip);
+#endif
+}
+
 /***                                Branch                                 ***/
 static inline void gen_goto_tb(DisasContext *ctx, int n, target_ulong dest)
 {
@@ -3407,6 +3424,7 @@ static void gen_b(DisasContext *ctx)
         target = li;
     if (LK(ctx->opcode))
         gen_setlr(ctx, ctx->nip);
+    gen_update_cfar(ctx, ctx->nip);
     gen_goto_tb(ctx, 0, target);
 }
 
@@ -3469,6 +3487,7 @@ static inline void gen_bcond(DisasContext *ctx, int type)
         }
         tcg_temp_free_i32(temp);
     }
+    gen_update_cfar(ctx, ctx->nip);
     if (type == BCOND_IM) {
         target_ulong li = (target_long)((int16_t)(BD(ctx->opcode)));
         if (likely(AA(ctx->opcode) == 0)) {
@@ -3580,6 +3599,7 @@ static void gen_rfi(DisasContext *ctx)
         gen_inval_exception(ctx, POWERPC_EXCP_PRIV_OPC);
         return;
     }
+    gen_update_cfar(ctx, ctx->nip);
     gen_helper_rfi();
     gen_sync_exception(ctx);
 #endif
@@ -3596,6 +3616,7 @@ static void gen_rfid(DisasContext *ctx)
         gen_inval_exception(ctx, POWERPC_EXCP_PRIV_OPC);
         return;
     }
+    gen_update_cfar(ctx, ctx->nip);
     gen_helper_rfid();
     gen_sync_exception(ctx);
 #endif
@@ -9263,6 +9284,12 @@ void cpu_dump_state (CPUState *env, FILE *f, fprintf_function cpu_fprintf,
          */
     }
 
+#if defined(TARGET_PPC64)
+    if (env->flags & POWERPC_FLAG_CFAR) {
+        cpu_fprintf(f, " CFAR " TARGET_FMT_lx"\n", env->cfar);
+    }
+#endif
+
     switch (env->mmu_model) {
     case POWERPC_MMU_32B:
     case POWERPC_MMU_601:
@@ -9371,6 +9398,7 @@ static inline void gen_intermediate_code_internal(CPUState *env,
     ctx.le_mode = env->hflags & (1 << MSR_LE) ? 1 : 0;
 #if defined(TARGET_PPC64)
     ctx.sf_mode = msr_sf;
+    ctx.has_cfar = !!(env->flags & POWERPC_FLAG_CFAR);
 #endif
     ctx.fpu_enabled = msr_fp;
     if ((env->flags & POWERPC_FLAG_SPE) && msr_spe)
diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
index 9ea193d..211f3bd 100644
--- a/target-ppc/translate_init.c
+++ b/target-ppc/translate_init.c
@@ -129,6 +129,19 @@ static void spr_write_lr (void *opaque, int sprn, int gprn)
     tcg_gen_mov_tl(cpu_lr, cpu_gpr[gprn]);
 }
 
+/* CFAR */
+#if defined(TARGET_PPC64) && !defined(CONFIG_USER_ONLY)
+static void spr_read_cfar (void *opaque, int gprn, int sprn)
+{
+    tcg_gen_mov_tl(cpu_gpr[gprn], cpu_cfar);
+}
+
+static void spr_write_cfar (void *opaque, int sprn, int gprn)
+{
+    tcg_gen_mov_tl(cpu_cfar, cpu_gpr[gprn]);
+}
+#endif /* defined(TARGET_PPC64) && !defined(CONFIG_USER_ONLY) */
+
 /* CTR */
 static void spr_read_ctr (void *opaque, int gprn, int sprn)
 {
@@ -6489,7 +6502,7 @@ static void init_proc_970MP (CPUPPCState *env)
 #define POWERPC_BFDM_POWER7   (bfd_mach_ppc64)
 #define POWERPC_FLAG_POWER7   (POWERPC_FLAG_VRE | POWERPC_FLAG_SE |            \
                               POWERPC_FLAG_BE | POWERPC_FLAG_PMM |            \
-                              POWERPC_FLAG_BUS_CLK)
+                              POWERPC_FLAG_BUS_CLK | POWERPC_FLAG_CFAR)
 #define check_pow_POWER7    check_pow_nocheck
 
 static void init_proc_POWER7 (CPUPPCState *env)
@@ -6508,6 +6521,14 @@ static void init_proc_POWER7 (CPUPPCState *env)
                  &spr_read_purr, SPR_NOACCESS,
                  &spr_read_purr, SPR_NOACCESS,
                  0x00000000);
+    spr_register(env, SPR_CFAR, "SPR_CFAR",
+                 SPR_NOACCESS, SPR_NOACCESS,
+                 &spr_read_cfar, &spr_write_cfar,
+                 0x00000000);
+    spr_register(env, SPR_DSCR, "SPR_DSCR",
+                 SPR_NOACCESS, SPR_NOACCESS,
+                 &spr_read_generic, &spr_write_generic,
+                 0x00000000);
 #endif /* !CONFIG_USER_ONLY */
     /* Memory management */
     /* XXX : not implemented */
-- 
1.6.0.2