diff --git a/nova/tests/unit/virt/libvirt/fakelibvirt.py b/nova/tests/unit/virt/libvirt/fakelibvirt.py
index 51918b6d51f9..7992b1af7b8c 100644
--- a/nova/tests/unit/virt/libvirt/fakelibvirt.py
+++ b/nova/tests/unit/virt/libvirt/fakelibvirt.py
@@ -1786,6 +1786,11 @@ class FakeLibvirtFixture(fixtures.Fixture):
             'nova.virt.libvirt.driver.LibvirtDriver'
             '._get_host_sysinfo_serial_os', return_value=uuids.machine_id))
 
+        # Stub out _log_host_capabilities since it logs a giant string at INFO
+        # and we don't want that to blow up the subunit parser in test runs.
+        self.useFixture(fixtures.MockPatch(
+            'nova.virt.libvirt.host.Host._log_host_capabilities'))
+
         disable_event_thread(self)
 
         if self.stub_os_vif:
diff --git a/nova/virt/libvirt/host.py b/nova/virt/libvirt/host.py
index baf643496a39..c3ee485780f2 100644
--- a/nova/virt/libvirt/host.py
+++ b/nova/virt/libvirt/host.py
@@ -635,6 +635,13 @@ class Host(object):
 
         return online_cpus
 
+    @staticmethod
+    def _log_host_capabilities(xmlstr):
+        # NOTE(mriedem): This looks a bit weird but we do this so we can stub
+        # out this method in unit/functional test runs since the xml string is
+        # big and it can cause subunit parsing to fail (see bug 1813147).
+        LOG.info("Libvirt host capabilities %s", xmlstr)
+
     def get_capabilities(self):
         """Returns the host capabilities information
 
@@ -647,7 +654,7 @@ class Host(object):
         """
         if not self._caps:
             xmlstr = self.get_connection().getCapabilities()
-            LOG.info("Libvirt host capabilities %s", xmlstr)
+            self._log_host_capabilities(xmlstr)
             self._caps = vconfig.LibvirtConfigCaps()
             self._caps.parse_str(xmlstr)
             # NOTE(mriedem): Don't attempt to get baseline CPU features