Index: /trunk/doc/manual/en_US/user_BasicConcepts.xml
===================================================================
--- /trunk/doc/manual/en_US/user_BasicConcepts.xml	(revision 51260)
+++ /trunk/doc/manual/en_US/user_BasicConcepts.xml	(revision 51261)
@@ -1386,4 +1386,16 @@
       VM is powered off and remains persistent until changed.</para>
     </sect2>
+
+    <sect2 id="efibootargs">
+      <title>Specifying boot arguments</title>
+
+      <para>It is currently not possible to manipulate EFI variables from within a running guest
+      (e.g., setting the "boot-args" variable by running the <computeroutput>nvram</computeroutput> tool in a Mac OS X guest will not work).
+      As an alternative way, "VBoxInternal2/EfiBootArgs" extradata can be passed to a VM in order to set
+      the "boot-args" variable. To change the "boot-args" EFI variable:
+      <screen>VBoxManage setextradata "VM name" VBoxInternal2/EfiBootArgs &lt;value&gt;</screen>
+      </para>
+    </sect2>
+
   </sect1>
 </chapter>
Index: /trunk/doc/manual/en_US/user_KnownIssues.xml
===================================================================
--- /trunk/doc/manual/en_US/user_KnownIssues.xml	(revision 51260)
+++ /trunk/doc/manual/en_US/user_KnownIssues.xml	(revision 51261)
@@ -225,4 +225,9 @@
                 messages by issuing this command:<screen>VBoxManage setextradata "VM name" "VBoxInternal2/EfiBootArgs" "  "</screen>To
                 revert to the previous behavior, use:<screen>VBoxManage setextradata "VM name" "VBoxInternal2/EfiBootArgs" ""</screen></para>
+              </listitem>
+
+              <listitem>
+                <para>It is currently not possible to start a Mac OS X guest in safe mode by specifying "-x" option
+                in "VBoxInternal2/EfiBootArgs" extradata.</para>
               </listitem>
             </itemizedlist></para>