diff --git a/nova/virt/libvirt/config.py b/nova/virt/libvirt/config.py
index a931b57..4e8f545 100644
--- a/nova/virt/libvirt/config.py
+++ b/nova/virt/libvirt/config.py
@@ -311,6 +311,9 @@ class LibvirtConfigCPU(LibvirtConfigObject):
         return cpu
 
     def add_feature(self, feat):
+        for feature in self.features:
+            if feat.name == feature.name:
+                return
         self.features.append(feat)