Index: /trunk/src/VBox/Devices/Bus/DevPCI.cpp
===================================================================
--- /trunk/src/VBox/Devices/Bus/DevPCI.cpp	(revision 38851)
+++ /trunk/src/VBox/Devices/Bus/DevPCI.cpp	(revision 38852)
@@ -2099,4 +2099,8 @@
     pBus->pPciHlpR0 = pBus->pPciHlpR3->pfnGetR0Helpers(pDevIns);
 
+    /* Disable default device locking. */
+    rc = PDMDevHlpSetDeviceCritSect(pDevIns, PDMDevHlpCritSectGetNop(pDevIns));
+    AssertRCReturn(rc, rc);
+
     /*
      * Fill in PCI configs and add them to the bus.