xend: NUMA: fix division by zero on unpopulated nodes

nodes without memory will currently be disabled by also moving the
physical cores connected to them to other nodes. This leads to nodes
without CPUs and thus to a division by zero in the node allocation
algorithm.  Attached patch fixes this by checking for 0 before the
division. This fixes domain creation on boxes with memory-less nodes.

Signed-off-by: Andre Przywara <andre.przywara@amd.com>

tools/python/xen/xend/XendDomainInfo.py

@@ -2709,9 +2709,12 @@ class XendDomainInfo:
                                     nodeload[i] += 1
                                     break
                 for i in range(0, nr_nodes):
-                    nodeload[i] = int(nodeload[i] * 16 / len(info['node_to_cpu'][i]))
-                    if len(info['node_to_cpu'][i]) == 0 or i not in node_list:
+                    if len(info['node_to_cpu'][i]) == 0:
                         nodeload[i] += 8
+                    else:
+                        nodeload[i] = int(nodeload[i] * 16 / len(info['node_to_cpu'][i]))
+                        if i not in node_list:
+                            nodeload[i] += 8
                 return map(lambda x: x[0], sorted(enumerate(nodeload), key=lambda x:x[1]))
 
             info = xc.physinfo()