Index: /trunk/src/VBox/ValidationKit/bootsectors/bs3kit/Makefile.kmk
===================================================================
--- /trunk/src/VBox/ValidationKit/bootsectors/bs3kit/Makefile.kmk	(revision 59893)
+++ /trunk/src/VBox/ValidationKit/bootsectors/bs3kit/Makefile.kmk	(revision 59894)
@@ -96,4 +96,5 @@
        bs3-cmn-SwitchToRing3.asm \
        bs3-cmn-SwitchTo16Bit.asm \
+       bs3-cmn-SwitchTo16BitV86.asm \
        bs3-cmn-SwitchTo32Bit.asm \
        bs3-cmn-SwitchTo64Bit.asm \
Index: /trunk/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-SwitchTo16BitV86.asm
===================================================================
--- /trunk/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-SwitchTo16BitV86.asm	(revision 59894)
+++ /trunk/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-SwitchTo16BitV86.asm	(revision 59894)
@@ -0,0 +1,113 @@
+; $Id$
+;; @file
+; BS3Kit - Bs3SwitchTo16BitV86
+;
+
+;
+; Copyright (C) 2007-2016 Oracle Corporation
+;
+; This file is part of VirtualBox Open Source Edition (OSE), as
+; available from http://www.virtualbox.org. This file is free software;
+; you can redistribute it and/or modify it under the terms of the GNU
+; General Public License (GPL) as published by the Free Software
+; Foundation, in version 2 as it comes in the "COPYING" file of the
+; VirtualBox OSE distribution. VirtualBox OSE is distributed in the
+; hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
+;
+; The contents of this file may alternatively be used under the terms
+; of the Common Development and Distribution License Version 1.0
+; (CDDL) only, as it comes in the "COPYING.CDDL" file of the
+; VirtualBox OSE distribution, in which case the provisions of the
+; CDDL are applicable instead of those of the GPL.
+;
+; You may elect to license modified versions of this file under the
+; terms and conditions of either the GPL or the CDDL or both.
+;
+
+%include "bs3kit-template-header.mac"
+
+%if TMPL_BITS != 64
+
+BS3_EXTERN_DATA16   g_bBs3CurrentMode
+BS3_EXTERN_CMN      Bs3SwitchToRing0
+TMPL_BEGIN_TEXT
+
+
+;;
+; @cproto   BS3_DECL(void) Bs3SwitchTo16BitV86(void);
+;
+BS3_PROC_BEGIN_CMN Bs3SwitchTo16BitV86
+        ; Construct basic v8086 return frame.
+        BS3_ONLY_16BIT_STMT push gs
+        BS3_ONLY_16BIT_STMT movzx esp, sp
+        push    dword fs
+        push    dword BS3_SEL_DATA16    ; ES
+        push    dword BS3_SEL_DATA16    ; DS
+        push    dword ss
+        push    dword 0                 ; return ESP, later.
+        pushfd
+        or      dword [esp], X86_EFL_VM ; Set the VM flag in EFLAGS.
+        push    dword BS3_SEL_TEXT16
+        push    word 0
+ %if TMPL_BITS == 16
+        push    word [esp + 2 + 7 * 4 + 2]
+ %else
+        push    word [esp + 2 + 7 * 4]
+ %endif
+        ; Save registers and stuff.
+        push    eax
+ %if TMPL_BITS == 16
+        push    ds
+
+        ; Check g_bBs3CurrentMode whether we're in v8086 mode or not.
+        mov     ax, seg g_bBs3CurrentMode
+        mov     ds, ax
+        mov     al, [g_bBs3CurrentMode]
+        and     al, BS3_MODE_CODE_MASK
+        cmp     al, BS3_MODE_CODE_V86
+        jne     .not_v8086
+
+        pop     ds
+        pop     eax
+        add     xSP, (9-1)*4
+        ret
+
+.not_v8086:
+        pop     ax                      ; Drop the push ds so the stacks are identical. Keep DS = BS3DATA16 though.
+ %endif
+
+        ; Ensure that we're in ring-0.
+        mov     ax, ss
+        test    ax, 3
+        jz      .is_ring0
+        call    Bs3SwitchToRing0
+.is_ring0:
+
+        ; Update globals.
+        and     byte [g_bBs3CurrentMode], ~BS3_MODE_CODE_MASK
+        or      byte [g_bBs3CurrentMode], BS3_MODE_CODE_16
+
+ %if TMPL_BITS != 16
+        ; Set GS.
+        mov     ax, gs
+        mov     [xSP + 4 + 20h], ax
+ %endif
+
+        ; Thunk SS:ESP, first step: calc flat address.
+        lea     eax, [esp + 4 + 24h]
+        push    eax
+        push    ss
+;        call    Bs3SelFar32ToFlat32
+
+        ; Second step: Calc realmode segment and offset.
+
+
+        ; Return to v8086 mode.
+        pop     eax
+        iretd
+BS3_PROC_END_CMN   Bs3SwitchTo16Bit
+
+
+
+%endif ; ! 64-bit
+