Index: /trunk/src/VBox/VMM/VMMR0/GMMR0.cpp
===================================================================
--- /trunk/src/VBox/VMM/VMMR0/GMMR0.cpp	(revision 29574)
+++ /trunk/src/VBox/VMM/VMMR0/GMMR0.cpp	(revision 29575)
@@ -3212,5 +3212,10 @@
             *ppvR3 = RTR0MemObjAddressR3(pChunk->paMappings[i].MapObj);
             Log(("gmmR0MapChunk: chunk %#x is already mapped at %p!\n", pChunk->Core.Key, *ppvR3));
+#ifdef VBOX_WITH_PAGE_SHARING
+            /* The ring-3 chunk cache can be out of sync; don't fail. */
+            return VINF_SUCCESS;
+#else
             return VERR_GMM_CHUNK_ALREADY_MAPPED;
+#endif
         }
     }