spapr_cpu_core: rewrite machine type sanity check

This makes the code easier to understand and it is consistent with what
we already do for PHBs.
Signed-off-by: NGreg Kurz <groug@kaod.org>
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>

hw/ppc/spapr_cpu_core.c

@@ -137,7 +137,12 @@ error:
 
 static void spapr_cpu_core_realize(DeviceState *dev, Error **errp)
 {
-    sPAPRMachineState *spapr;
+    /* We don't use SPAPR_MACHINE() in order to exit gracefully if the user
+     * tries to add a sPAPR CPU core to a non-pseries machine.
+     */
+    sPAPRMachineState *spapr =
+        (sPAPRMachineState *) object_dynamic_cast(qdev_get_machine(),
+                                                  TYPE_SPAPR_MACHINE);
     sPAPRCPUCore *sc = SPAPR_CPU_CORE(OBJECT(dev));
     sPAPRCPUCoreClass *scc = SPAPR_CPU_CORE_GET_CLASS(OBJECT(dev));
     CPUCore *cc = CPU_CORE(OBJECT(dev));
@@ -146,9 +151,8 @@ static void spapr_cpu_core_realize(DeviceState *dev, Error **errp)
     void *obj;
     int i, j;
 
-    spapr = (sPAPRMachineState *) qdev_get_machine();
-    if (!object_dynamic_cast((Object *) spapr, TYPE_SPAPR_MACHINE)) {
-        error_setg(errp, "spapr-cpu-core needs a pseries machine");
+    if (!spapr) {
+        error_setg(errp, TYPE_SPAPR_CPU_CORE " needs a pseries machine");
         return;
     }