Index: /trunk/src/VBox/VMM/VMMAll/PGMAllPool.cpp
===================================================================
--- /trunk/src/VBox/VMM/VMMAll/PGMAllPool.cpp	(revision 22711)
+++ /trunk/src/VBox/VMM/VMMAll/PGMAllPool.cpp	(revision 22712)
@@ -1622,4 +1622,6 @@
         return false;
 
+    GCPhys = GCPhys & ~(RTGCPHYS)(PAGE_SIZE - 1);
+
     for (unsigned i = 0; i < RT_ELEMENTS(pPool->aIdxDirtyPages); i++)
     {