Index: /trunk/src/VBox/Devices/VirtIO/Virtio.cpp
===================================================================
--- /trunk/src/VBox/Devices/VirtIO/Virtio.cpp	(revision 71111)
+++ /trunk/src/VBox/Devices/VirtIO/Virtio.cpp	(revision 71112)
@@ -579,5 +579,14 @@
                 rc = pCallbacks->pfnReset(pState);
             else if (fHasBecomeReady)
+            {
+                /* Older hypervisors were lax and did not enforce bus mastering. Older guests
+                 * (Linux prior to 2.6.34, NetBSD 6.x) were lazy and did not enable bus mastering.
+                 * We automagically enable bus mastering on driver initialization to make existing
+                 * drivers work.
+                 */
+                PDMPciDevSetCommand(&pState->pciDevice, PDMPciDevGetCommand(&pState->pciDevice) | PCI_COMMAND_BUSMASTER);
+
                 pCallbacks->pfnReady(pState);
+            }
             break;