xend, NUMA: Fix computation of needed nodes

Enumerate the best nodes and add CPU affinity until all VCPUs can be
backed by at least one physical core. This should fix problems with
asymmetric NUMA configurations and cropped number of CPUs in Xen.

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

tools/python/xen/xend/XendDomainInfo.py

@@ -2724,13 +2724,12 @@ class XendDomainInfo:
                         candidate_node_list.append(i)
                 best_node = find_relaxed_node(candidate_node_list)[0]
                 cpumask = info['node_to_cpu'][best_node]
-                cores_per_node = info['nr_cpus'] / info['nr_nodes']
-                nodes_required = (self.info['VCPUs_max'] + cores_per_node - 1) / cores_per_node
-                if nodes_required > 1:
-                    log.debug("allocating %d NUMA nodes", nodes_required)
-                    best_nodes = find_relaxed_node(filter(lambda x: x != best_node, range(0,info['nr_nodes'])))
-                    for i in best_nodes[:nodes_required - 1]:
-                        cpumask = cpumask + info['node_to_cpu'][i]
+                best_nodes = find_relaxed_node(filter(lambda x: x != best_node, range(0,info['nr_nodes'])))
+                for node_idx in best_nodes:
+                    if len(cpumask) >= self.info['VCPUs_max']:
+                        break
+                    cpumask = cpumask + info['node_to_cpu'][node_idx]
+                    log.debug("allocating additional NUMA node %d", node_idx)
                 for v in range(0, self.info['VCPUs_max']):
                     xc.vcpu_setaffinity(self.domid, v, cpumask)
         return index