ppc: Add has_smt_siblings property to CPUPPCState

The decision to branch out to a slower SMT path in instruction
emulation will become a bit more complicated with the way that
"big-core" topology that will be implemented in subsequent changes.
Hide these details from the wider CPU emulation code with a bool
has_smt_siblings flag that can be set by machine initialisation.

Reviewed-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

hw/ppc/pnv_core.c

@@ -288,6 +288,9 @@ static void pnv_core_realize(DeviceState *dev, Error **errp)
         cpu = POWERPC_CPU(obj);
 
         pc->threads[i] = POWERPC_CPU(obj);
+        if (cc->nr_threads > 1) {
+            cpu->env.has_smt_siblings = true;
+        }
 
         snprintf(name, sizeof(name), "thread[%d]", i);
         object_property_add_child(OBJECT(pc), name, obj);

hw/ppc/spapr_cpu_core.c

@@ -349,9 +349,15 @@ static void spapr_cpu_core_realize(DeviceState *dev, Error **errp)
     qemu_register_reset(spapr_cpu_core_reset_handler, sc);
     sc->threads = g_new0(PowerPCCPU *, cc->nr_threads);
     for (i = 0; i < cc->nr_threads; i++) {
-        sc->threads[i] = spapr_create_vcpu(sc, i, errp);
-        if (!sc->threads[i] ||
-            !spapr_realize_vcpu(sc->threads[i], spapr, sc, i, errp)) {
+        PowerPCCPU *cpu;
+
+        cpu = spapr_create_vcpu(sc, i, errp);
+        sc->threads[i] = cpu;
+        if (cpu && cc->nr_threads > 1) {
+            cpu->env.has_smt_siblings = true;
+        }
+
+        if (!cpu || !spapr_realize_vcpu(cpu, spapr, sc, i, errp)) {
             spapr_cpu_core_unrealize(dev);
             return;
         }

target/ppc/cpu.h

@@ -1248,6 +1248,7 @@ struct CPUArchState {
     int access_type;
 
     /* For SMT processors */
+    bool has_smt_siblings;
     int core_index;
 
 #if !defined(CONFIG_USER_ONLY)
@@ -1514,7 +1515,7 @@ struct PowerPCCPUClass {
 
 static inline bool ppc_cpu_core_single_threaded(CPUState *cs)
 {
-    return cs->nr_threads == 1;
+    return !POWERPC_CPU(cs)->env.has_smt_siblings;
 }
 
 static inline bool ppc_cpu_lpar_single_threaded(CPUState *cs)