domain: cpu: Rework vcpus setting slightly

Move it to Guest, where we have a more hollistic view of the issues.
This will be needed in later patches

virtinst/domain/cpu.py

@@ -208,10 +208,7 @@ class DomainCpu(XMLBuilder):
         Determine the CPU count represented by topology, or 1 if
         no topology is set
         """
-        self.set_topology_defaults()
-        if self.has_topology():
-            return self.sockets * self.cores * self.threads
-        return 1
+        return (self.sockets or 1) * (self.cores or 1) * (self.threads or 1)
 
     def has_topology(self):
         """
@@ -219,14 +216,11 @@ class DomainCpu(XMLBuilder):
         """
         return bool(self.sockets or self.cores or self.threads)
 
-    def set_topology_defaults(self, vcpus=None):
+    def set_topology_defaults(self, vcpus):
         """
         Fill in unset topology values, using the passed vcpus count if
         required
         """
-        if not self.has_topology():
-            return
-
         if vcpus is None:
             if self.sockets is None:
                 self.sockets = 1
@@ -306,8 +300,6 @@ class DomainCpu(XMLBuilder):
             self._validate_default_host_model_only(guest)
 
     def set_defaults(self, guest):
-        self.set_topology_defaults(guest.vcpus)
-
         if not self.conn.is_test() and not self.conn.is_qemu():
             return
         if (self.get_xml().strip() or

virtinst/guest.py

@@ -657,14 +657,25 @@ class Guest(XMLBuilder):
             logging.warning("KVM acceleration not available, using '%s'",
                             self.type)
 
-    def set_defaults(self, _guest):
-        if not self.uuid:
-            self.uuid = Guest.generate_uuid(self.conn)
-        if not self.vcpus and self.cpu.has_topology():
+    def sync_vcpus_topology(self):
+        """
+        <cpu> topology count and <vcpus> always need to match. Handle
+        the syncing here since we are less constrained then doing it
+        in CPU set_defaults
+        """
+        if not self.cpu.has_topology():
+            return
+        if not self.vcpus:
             self.vcpus = self.cpu.vcpus_from_topology()
+        self.cpu.set_topology_defaults(self.vcpus)
 
+    def set_defaults(self, _guest):
         self.set_capabilities_defaults()
 
+        if not self.uuid:
+            self.uuid = Guest.generate_uuid(self.conn)
+
+        self.sync_vcpus_topology()
         self._set_default_resources()
         self._set_default_machine()
         self._set_default_uefi()