[RFC PATCH 3/5] target/ppc: Add support for SMT CTRL register

[Nicholas Piggin <npiggin@gmail.com>]

A relatively simple case to begin with, CTRL is a SMT shared register
where reads and writes need to synchronise against state changes by
other threads in the core.

Atomic serialisation operations are used to achieve this.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 target/ppc/helper.h      |  2 ++
 target/ppc/misc_helper.c | 33 +++++++++++++++++++++++++++++++++
 target/ppc/translate.c   | 18 +++++++++++++++++-
 3 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/target/ppc/helper.h b/target/ppc/helper.h
index 38efbc351c..fda40b8a60 100644
--- a/target/ppc/helper.h
+++ b/target/ppc/helper.h
@@ -704,6 +704,8 @@ DEF_HELPER_3(store_dcr, void, env, tl, tl)
 
 DEF_HELPER_2(load_dump_spr, void, env, i32)
 DEF_HELPER_2(store_dump_spr, void, env, i32)
+DEF_HELPER_3(spr_write_CTRL, void, env, i32, tl)
+
 DEF_HELPER_4(fscr_facility_check, void, env, i32, i32, i32)
 DEF_HELPER_4(msr_facility_check, void, env, i32, i32, i32)
 DEF_HELPER_FLAGS_1(load_tbl, TCG_CALL_NO_RWG, tl, env)
diff --git a/target/ppc/misc_helper.c b/target/ppc/misc_helper.c
index 40ddc5c08c..ffe54a4310 100644
--- a/target/ppc/misc_helper.c
+++ b/target/ppc/misc_helper.c
@@ -43,6 +43,39 @@ void helper_store_dump_spr(CPUPPCState *env, uint32_t sprn)
              env->spr[sprn]);
 }
 
+void helper_spr_write_CTRL(CPUPPCState *env, uint32_t sprn,
+                           target_ulong val)
+{
+    CPUState *cs = env_cpu(env);
+    CPUState *ccs;
+    uint32_t nr_threads = cs->nr_threads;
+    uint32_t core_id = env->spr[SPR_PIR] & ~(nr_threads - 1);
+    uint32_t run = val & 1;
+    uint32_t ts, ts_mask;
+
+    assert(sprn == SPR_CTRL);
+    assert(core_id == env->spr[SPR_PIR] - env->spr[SPR_TIR]);
+
+    env->spr[sprn] &= ~1U;
+    env->spr[sprn] |= run;
+
+    ts_mask = ~(1U << (8 + env->spr[SPR_TIR]));
+    ts = run << (8 + env->spr[SPR_TIR]);
+
+    CPU_FOREACH(ccs) {
+        CPUPPCState *cenv = &POWERPC_CPU(ccs)->env;
+        uint32_t ccore_id = cenv->spr[SPR_PIR] & ~(nr_threads - 1);
+
+        assert(ccore_id == cenv->spr[SPR_PIR] - cenv->spr[SPR_TIR]);
+
+        if (ccore_id == core_id) {
+            cenv->spr[sprn] &= ts_mask;
+            cenv->spr[sprn] |= ts;
+        }
+    }
+}
+
+
 #ifdef TARGET_PPC64
 static void raise_hv_fu_exception(CPUPPCState *env, uint32_t bit,
                                   const char *caller, uint32_t cause,
diff --git a/target/ppc/translate.c b/target/ppc/translate.c
index 72270c2163..31821f92f5 100644
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -443,7 +443,7 @@ void spr_write_generic32(DisasContext *ctx, int sprn, int gprn)
 #endif
 }
 
-void spr_write_CTRL(DisasContext *ctx, int sprn, int gprn)
+static void spr_write_CTRL_ST(DisasContext *ctx, int sprn, int gprn)
 {
     /* This does not implement >1 thread */
     TCGv t0 = tcg_temp_new();
@@ -452,6 +452,22 @@ void spr_write_CTRL(DisasContext *ctx, int sprn, int gprn)
     tcg_gen_shli_tl(t1, t0, 8); /* Duplicate the bit in TS */
     tcg_gen_or_tl(t1, t1, t0);
     gen_store_spr(sprn, t1);
+}
+
+void spr_write_CTRL(DisasContext *ctx, int sprn, int gprn)
+{
+    if (!(ctx->flags & POWERPC_FLAG_SMT)) {
+        spr_write_CTRL_ST(ctx, sprn, gprn);
+        goto out;
+    }
+
+    if (!gen_serialize(ctx)) {
+        return;
+    }
+
+    gen_helper_spr_write_CTRL(cpu_env, tcg_constant_i32(sprn),
+                              cpu_gpr[gprn]);
+out:
     spr_store_dump_spr(sprn);
 
     /*
-- 
2.40.1