Index: /trunk/src/VBox/VMM/VMMR3/PDMAsyncCompletionFileNormal.cpp
===================================================================
--- /trunk/src/VBox/VMM/VMMR3/PDMAsyncCompletionFileNormal.cpp	(revision 66652)
+++ /trunk/src/VBox/VMM/VMMR3/PDMAsyncCompletionFileNormal.cpp	(revision 66653)
@@ -1465,7 +1465,9 @@
              * the transfer needs to be continued.
              */
-            if (RT_UNLIKELY(   cbTransfered < pTask->DataSeg.cbSeg
+            pTask->cbTransfered += cbTransfered;
+
+            if (RT_UNLIKELY(   pTask->cbTransfered < pTask->DataSeg.cbSeg
                             || (   pTask->cbBounceBuffer
-                                && cbTransfered < pTask->cbBounceBuffer)))
+                                && pTask->cbTransfered < pTask->cbBounceBuffer)))
             {
                 RTFOFF offStart;
@@ -1480,14 +1482,14 @@
                 {
                     AssertPtr(pTask->pvBounceBuffer);
-                    offStart     = (pTask->Off & ~((RTFOFF)512-1)) + cbTransfered;
-                    cbToTransfer = pTask->cbBounceBuffer - cbTransfered;
-                    pbBuf        = (uint8_t *)pTask->pvBounceBuffer + cbTransfered;
+                    offStart     = (pTask->Off & ~((RTFOFF)512-1)) + pTask->cbTransfered;
+                    cbToTransfer = pTask->cbBounceBuffer - pTask->cbTransfered;
+                    pbBuf        = (uint8_t *)pTask->pvBounceBuffer + pTask->cbTransfered;
                 }
                 else
                 {
                     Assert(!pTask->pvBounceBuffer);
-                    offStart     = pTask->Off + cbTransfered;
-                    cbToTransfer = pTask->DataSeg.cbSeg - cbTransfered;
-                    pbBuf        = (uint8_t *)pTask->DataSeg.pvSeg + cbTransfered;
+                    offStart     = pTask->Off + pTask->cbTransfered;
+                    cbToTransfer = pTask->DataSeg.cbSeg - pTask->cbTransfered;
+                    pbBuf        = (uint8_t *)pTask->DataSeg.pvSeg + pTask->cbTransfered;
                 }
 
@@ -1524,4 +1526,6 @@
                 RTFOFF offStart = pTask->Off & ~(RTFOFF)(512-1);
                 size_t cbToTransfer = RT_ALIGN_Z(pTask->DataSeg.cbSeg + (pTask->Off - offStart), 512);
+
+                pTask->cbTransfered = 0;
 
                 /* Grow the file if needed. */
Index: /trunk/src/VBox/VMM/include/PDMAsyncCompletionFileInternal.h
===================================================================
--- /trunk/src/VBox/VMM/include/PDMAsyncCompletionFileInternal.h	(revision 66652)
+++ /trunk/src/VBox/VMM/include/PDMAsyncCompletionFileInternal.h	(revision 66653)
@@ -484,4 +484,6 @@
     /** Start offset */
     RTFOFF                               Off;
+    /** Amount of data transfered so far. */
+    size_t                               cbTransfered;
     /** Data segment. */
     RTSGSEG                              DataSeg;