diff --git a/nova/virt/hardware.py b/nova/virt/hardware.py
index 5e51d50de0df..98ad15419a7f 100644
--- a/nova/virt/hardware.py
+++ b/nova/virt/hardware.py
@@ -1200,8 +1200,16 @@ def numa_fit_instance_to_host(
     InstanceNUMATopology with it's cell ids set to host cell id's of
     the first successful permutation, or None.
     """
-    if (not (host_topology and instance_topology) or
-        len(host_topology) < len(instance_topology)):
+    if not (host_topology and instance_topology):
+        LOG.debug("Require both a host and instance NUMA topology to "
+                  "fit instance on host.")
+        return
+    elif len(host_topology) < len(instance_topology):
+        LOG.debug("There are not enough free cores on the system to schedule "
+                  "the instance correctly. Required: %(required)s, actual: "
+                  "%(actual)s",
+                  {'required': len(instance_topology),
+                   'actual': len(host_topology)})
         return
     else:
         # TODO(ndipanov): We may want to sort permutations differently