target/ppc: Implement SPRC/SPRD SPRs

This implements the POWER SPRC/SPRD SPRs, and SCRATCH0-7 registers that
can be accessed via these indirect SPRs.

SCRATCH registers only provide storage, but they are used by firmware
for low level crash and progress data, so this implementation logs
writes to the registers to help with analysis.

Reviewed-by: Glenn Miles <milesg@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

6 files changed, 105 insertions, 2 deletions

diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
index 823be85..e4c342b 100644
--- a/target/ppc/cpu.h
+++ b/target/ppc/cpu.h
@@ -1264,6 +1264,9 @@ struct CPUArchState {
     ppc_slb_t slb[MAX_SLB_ENTRIES]; /* PowerPC 64 SLB area */
     struct CPUBreakpoint *ciabr_breakpoint;
     struct CPUWatchpoint *dawr0_watchpoint;
+
+    /* POWER CPU regs/state */
+    target_ulong scratch[8]; /* SCRATCH registers (shared across core) */
 #endif
     target_ulong sr[32];   /* segment registers */
     uint32_t nb_BATs;      /* number of BATs */
@@ -1806,9 +1809,9 @@ void ppc_compat_add_property(Object *obj, const char *name,
 #define SPR_SPRG2             (0x112)
 #define SPR_SPRG3             (0x113)
 #define SPR_SPRG4             (0x114)
-#define SPR_SCOMC             (0x114)
+#define SPR_POWER_SPRC        (0x114)
 #define SPR_SPRG5             (0x115)
-#define SPR_SCOMD             (0x115)
+#define SPR_POWER_SPRD        (0x115)
 #define SPR_SPRG6             (0x116)
 #define SPR_SPRG7             (0x117)
 #define SPR_ASR               (0x118)
diff --git a/target/ppc/cpu_init.c b/target/ppc/cpu_init.c
index d181adc..8cfaee6 100644
--- a/target/ppc/cpu_init.c
+++ b/target/ppc/cpu_init.c
@@ -5777,6 +5777,16 @@ static void register_power_common_book4_sprs(CPUPPCState *env)
                  SPR_NOACCESS, SPR_NOACCESS,
                  &spr_read_generic, &spr_core_write_generic,
                  0x00000000);
+    spr_register_hv(env, SPR_POWER_SPRC, "SPRC",
+                 SPR_NOACCESS, SPR_NOACCESS,
+                 SPR_NOACCESS, SPR_NOACCESS,
+                 &spr_read_generic, &spr_write_sprc,
+                 0x00000000);
+    spr_register_hv(env, SPR_POWER_SPRD, "SPRD",
+                 SPR_NOACCESS, SPR_NOACCESS,
+                 SPR_NOACCESS, SPR_NOACCESS,
+                 &spr_read_sprd, &spr_write_sprd,
+                 0x00000000);
 #endif
 }
 
diff --git a/target/ppc/helper.h b/target/ppc/helper.h
index 09d50f9..57bf835 100644
--- a/target/ppc/helper.h
+++ b/target/ppc/helper.h
@@ -730,6 +730,9 @@ DEF_HELPER_2(book3s_msgsndp, void, env, tl)
 DEF_HELPER_2(book3s_msgclrp, void, env, tl)
 DEF_HELPER_1(load_tfmr, tl, env)
 DEF_HELPER_2(store_tfmr, void, env, tl)
+DEF_HELPER_FLAGS_2(store_sprc, TCG_CALL_NO_RWG, void, env, tl)
+DEF_HELPER_FLAGS_1(load_sprd, TCG_CALL_NO_RWG_SE, tl, env)
+DEF_HELPER_FLAGS_2(store_sprd, TCG_CALL_NO_RWG, void, env, tl)
 #endif
 DEF_HELPER_2(store_sdr1, void, env, tl)
 DEF_HELPER_2(store_pidr, void, env, tl)
diff --git a/target/ppc/misc_helper.c b/target/ppc/misc_helper.c
index a67930d..fa47be2 100644
--- a/target/ppc/misc_helper.c
+++ b/target/ppc/misc_helper.c
@@ -307,6 +307,72 @@ void helper_store_dpdes(CPUPPCState *env, target_ulong val)
     }
     bql_unlock();
 }
+
+/* Indirect SCOM (SPRC/SPRD) access to SCRATCH0-7 are implemented. */
+void helper_store_sprc(CPUPPCState *env, target_ulong val)
+{
+    if (val & ~0x3f8ULL) {
+        qemu_log_mask(LOG_GUEST_ERROR, "Invalid SPRC register value "
+                      TARGET_FMT_lx"\n", val);
+        return;
+    }
+    env->spr[SPR_POWER_SPRC] = val;
+}
+
+target_ulong helper_load_sprd(CPUPPCState *env)
+{
+    target_ulong sprc = env->spr[SPR_POWER_SPRC];
+
+    switch (sprc & 0x3c0) {
+    case 0: /* SCRATCH0-7 */
+        return env->scratch[(sprc >> 3) & 0x7];
+    default:
+        qemu_log_mask(LOG_UNIMP, "mfSPRD: Unimplemented SPRC:0x"
+                                  TARGET_FMT_lx"\n", sprc);
+        break;
+    }
+    return 0;
+}
+
+static void do_store_scratch(CPUPPCState *env, int nr, target_ulong val)
+{
+    CPUState *cs = env_cpu(env);
+    CPUState *ccs;
+    uint32_t nr_threads = cs->nr_threads;
+
+    /*
+     * Log stores to SCRATCH, because some firmware uses these for debugging
+     * and logging, but they would normally be read by the BMC, which is
+     * not implemented in QEMU yet. This gives a way to get at the information.
+     * Could also dump these upon checkstop.
+     */
+    qemu_log("SPRD write 0x" TARGET_FMT_lx " to SCRATCH%d\n", val, nr);
+
+    if (nr_threads == 1) {
+        env->scratch[nr] = val;
+        return;
+    }
+
+    THREAD_SIBLING_FOREACH(cs, ccs) {
+        CPUPPCState *cenv = &POWERPC_CPU(ccs)->env;
+        cenv->scratch[nr] = val;
+    }
+}
+
+void helper_store_sprd(CPUPPCState *env, target_ulong val)
+{
+    target_ulong sprc = env->spr[SPR_POWER_SPRC];
+
+    switch (sprc & 0x3c0) {
+    case 0: /* SCRATCH0-7 */
+        do_store_scratch(env, (sprc >> 3) & 0x7, val);
+        break;
+    default:
+        qemu_log_mask(LOG_UNIMP, "mfSPRD: Unimplemented SPRC:0x"
+                                  TARGET_FMT_lx"\n", sprc);
+        break;
+    }
+}
 #endif /* defined(TARGET_PPC64) */
 
 void helper_store_pidr(CPUPPCState *env, target_ulong val)
diff --git a/target/ppc/spr_common.h b/target/ppc/spr_common.h
index 85f73b8..01aff44 100644
--- a/target/ppc/spr_common.h
+++ b/target/ppc/spr_common.h
@@ -207,6 +207,9 @@ void spr_write_lpcr(DisasContext *ctx, int sprn, int gprn);
 void spr_read_dexcr_ureg(DisasContext *ctx, int gprn, int sprn);
 void spr_read_ppr32(DisasContext *ctx, int sprn, int gprn);
 void spr_write_ppr32(DisasContext *ctx, int sprn, int gprn);
+void spr_write_sprc(DisasContext *ctx, int sprn, int gprn);
+void spr_read_sprd(DisasContext *ctx, int sprn, int gprn);
+void spr_write_sprd(DisasContext *ctx, int sprn, int gprn);
 #endif
 
 void register_low_BATs(CPUPPCState *env);
diff --git a/target/ppc/translate.c b/target/ppc/translate.c
index 64131bf..0bc16d7 100644
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -1301,6 +1301,24 @@ void spr_write_tfmr(DisasContext *ctx, int sprn, int gprn)
     gen_helper_store_tfmr(tcg_env, cpu_gpr[gprn]);
 }
 
+void spr_write_sprc(DisasContext *ctx, int sprn, int gprn)
+{
+    gen_helper_store_sprc(tcg_env, cpu_gpr[gprn]);
+}
+
+void spr_read_sprd(DisasContext *ctx, int gprn, int sprn)
+{
+    gen_helper_load_sprd(cpu_gpr[gprn], tcg_env);
+}
+
+void spr_write_sprd(DisasContext *ctx, int sprn, int gprn)
+{
+    if (!gen_serialize_core(ctx)) {
+        return;
+    }
+    gen_helper_store_sprd(tcg_env, cpu_gpr[gprn]);
+}
+
 void spr_write_lpcr(DisasContext *ctx, int sprn, int gprn)
 {
     translator_io_start(&ctx->base);