domain_conf: Add default memballoon in PostParse callbacks

This should be a no-op change for now.

src/conf/domain_conf.c

@@ -12205,19 +12205,6 @@ virDomainDefParseXML(xmlDocPtr xml,
 
         def->memballoon = memballoon;
         VIR_FREE(nodes);
-    } else {
-        if (def->virtType == VIR_DOMAIN_VIRT_XEN ||
-            def->virtType == VIR_DOMAIN_VIRT_QEMU ||
-            def->virtType == VIR_DOMAIN_VIRT_KQEMU ||
-            def->virtType == VIR_DOMAIN_VIRT_KVM) {
-            virDomainMemballoonDefPtr memballoon;
-            if (VIR_ALLOC(memballoon) < 0)
-                goto error;
-            memballoon->model = def->virtType == VIR_DOMAIN_VIRT_XEN ?
-                VIR_DOMAIN_MEMBALLOON_MODEL_XEN :
-                VIR_DOMAIN_MEMBALLOON_MODEL_VIRTIO;
-            def->memballoon = memballoon;
-        }
     }
 
     /* Parse the RNG device */

src/qemu/qemu_domain.c

@@ -784,6 +784,16 @@ qemuDomainDefPostParse(virDomainDefPtr def,
         return -1;
         }
     }
+
+    if (!def->memballoon) {
+        virDomainMemballoonDefPtr memballoon;
+        if (VIR_ALLOC(memballoon) < 0)
+            return -1;
+
+        memballoon->model = VIR_DOMAIN_MEMBALLOON_MODEL_VIRTIO;
+        def->memballoon = memballoon;
+    }
+
     return 0;
 }
 

src/xen/xen_driver.c

@@ -340,6 +340,15 @@ xenDomainDeviceDefPostParse(virDomainDeviceDefPtr dev,
         STRNEQ(def->os.type, "hvm"))
         dev->data.chr->targetType = VIR_DOMAIN_CHR_CONSOLE_TARGET_TYPE_XEN;
 
+    if (!def->memballoon) {
+        virDomainMemballoonDefPtr memballoon;
+        if (VIR_ALLOC(memballoon) < 0)
+            return -1;
+
+        memballoon->model = VIR_DOMAIN_MEMBALLOON_MODEL_XEN;
+        def->memballoon = memballoon;
+    }
+
     return 0;
 }