spapr: Simplify error path of spapr_core_plug()

spapr_core_pre_plug() already guarantees that the slot for the given core
ID is available. It is thus safe to assume that spapr_find_cpu_slot()
returns a slot during plug. Turn the error path into an assertion.
It is also safe to assume that no device is attached to the corresponding
DRC and that spapr_drc_attach() shouldn't fail.

Pass &error_abort to spapr_drc_attach() and simplify error handling.

Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <20201201113728.885700-4-groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

hw/ppc/spapr.c

@@ -3738,8 +3738,7 @@ int spapr_core_dt_populate(SpaprDrc *drc, SpaprMachineState *spapr,
     return 0;
 }
 
-static void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
-                            Error **errp)
+static void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev)
 {
     SpaprMachineState *spapr = SPAPR_MACHINE(OBJECT(hotplug_dev));
     MachineClass *mc = MACHINE_GET_CLASS(spapr);
@@ -3754,20 +3753,20 @@ static void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
     int i;
 
     core_slot = spapr_find_cpu_slot(MACHINE(hotplug_dev), cc->core_id, &index);
-    if (!core_slot) {
-        error_setg(errp, "Unable to find CPU core with core-id: %d",
-                   cc->core_id);
-        return;
-    }
+    g_assert(core_slot); /* Already checked in spapr_core_pre_plug() */
+
     drc = spapr_drc_by_id(TYPE_SPAPR_DRC_CPU,
                           spapr_vcpu_id(spapr, cc->core_id));
 
     g_assert(drc || !mc->has_hotpluggable_cpus);
 
     if (drc) {
-        if (!spapr_drc_attach(drc, dev, errp)) {
-            return;
-        }
+        /*
+         * spapr_core_pre_plug() already buys us this is a brand new
+         * core being plugged into a free slot. Nothing should already
+         * be attached to the corresponding DRC.
+         */
+        spapr_drc_attach(drc, dev, &error_abort);
 
         if (hotplugged) {
             /*
@@ -4009,7 +4008,7 @@ static void spapr_machine_device_plug(HotplugHandler *hotplug_dev,
     if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
         spapr_memory_plug(hotplug_dev, dev);
     } else if (object_dynamic_cast(OBJECT(dev), TYPE_SPAPR_CPU_CORE)) {
-        spapr_core_plug(hotplug_dev, dev, errp);
+        spapr_core_plug(hotplug_dev, dev);
     } else if (object_dynamic_cast(OBJECT(dev), TYPE_SPAPR_PCI_HOST_BRIDGE)) {
         spapr_phb_plug(hotplug_dev, dev);
     } else if (object_dynamic_cast(OBJECT(dev), TYPE_SPAPR_TPM_PROXY)) {