[PATCH v2 06/31] OvmfPkg/XenResetVector: Add new entry point for Xen PVH

["Anthony PERARD" <anthony.perard@citrix.com>]

This one enter directly in 32bits

Information on the expected state of the machine when this entry point
is used can be found at:
https://xenbits.xenproject.org/docs/unstable/misc/pvh.html

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
---
 {UefiCpuPkg/ResetVector/Vtf0 => OvmfPkg/XenResetVector}/Ia16/ResetVectorVtf0.asm | 18 +++++++-
 OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm                                       | 47 ++++++++++++++++++++
 OvmfPkg/XenResetVector/XenResetVector.nasmb                                      |  1 +
 3 files changed, 65 insertions(+), 1 deletion(-)

diff --git a/UefiCpuPkg/ResetVector/Vtf0/Ia16/ResetVectorVtf0.asm b/OvmfPkg/XenResetVector/Ia16/ResetVectorVtf0.asm
similarity index 76%
copy from UefiCpuPkg/ResetVector/Vtf0/Ia16/ResetVectorVtf0.asm
copy to OvmfPkg/XenResetVector/Ia16/ResetVectorVtf0.asm
index 142d9f3212..46eec66859 100644
--- a/UefiCpuPkg/ResetVector/Vtf0/Ia16/ResetVectorVtf0.asm
+++ b/OvmfPkg/XenResetVector/Ia16/ResetVectorVtf0.asm
@@ -3,6 +3,8 @@
 ; First code executed by processor after resetting.
 ;
 ; Copyright (c) 2008 - 2014, Intel Corporation. All rights reserved.<BR>
+; Copyright (c) 2019, Citrix Systems, Inc.
+;
 ; This program and the accompanying materials
 ; are licensed and made available under the terms and conditions of the BSD License
 ; which accompanies this distribution.  The full text of the license may be found at
@@ -27,9 +29,23 @@ ALIGN   16
 ; located just below 0x100000000 (4GB) in the firmware device.
 ;
 %ifdef ALIGN_TOP_TO_4K_FOR_PAGING
-    TIMES (0x1000 - ($ - EndOfPageTables) - 0x20) DB 0
+    TIMES (0x1000 - ($ - EndOfPageTables) - (fourGigabytes - xenPVHEntryPoint)) DB 0
 %endif
 
+BITS    32
+xenPVHEntryPoint:
+;
+; Entry point to use when running as a Xen PVH guest. (0xffffffd0)
+;
+; Description of the expected state of the machine when this entry point is
+; used can be found at:
+; https://xenbits.xenproject.org/docs/unstable/misc/pvh.html
+;
+    jmp     xenPVHMain
+
+BITS    16
+ALIGN   16
+
 applicationProcessorEntryPoint:
 ;
 ; Application Processors entry point
diff --git a/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm b/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm
new file mode 100644
index 0000000000..c4802bf4d1
--- /dev/null
+++ b/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm
@@ -0,0 +1,47 @@
+;------------------------------------------------------------------------------
+; @file
+; An entry point use by Xen when a guest is started in PVH mode.
+;
+; Copyright (c) 2019, Citrix Systems, Inc.
+;
+; This program and the accompanying materials are licensed and made available
+; under the terms and conditions of the BSD License which accompanies this
+; distribution.  The full text of the license may be found at
+; http://opensource.org/licenses/bsd-license.php
+;
+; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT
+; WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+;
+;------------------------------------------------------------------------------
+
+BITS    32
+
+xenPVHMain:
+    mov     di, 'BP'
+
+    ; ESP -  Initial value of the EAX register (BIST: Built-in Self Test)
+    mov     esp, eax
+
+    cli
+
+    mov     ebx, ADDR_OF(gdtr)
+    lgdt    [ebx]
+
+    mov     eax, SEC_DEFAULT_CR0
+    mov     cr0, eax
+
+    jmp     LINEAR_CODE_SEL:ADDR_OF(.jmpToNewCodeSeg)
+.jmpToNewCodeSeg:
+
+    mov     eax, SEC_DEFAULT_CR4
+    mov     cr4, eax
+
+    mov     ax, LINEAR_SEL
+    mov     ds, ax
+    mov     es, ax
+    mov     fs, ax
+    mov     gs, ax
+    mov     ss, ax
+
+    ; return to the Main16
+    OneTimeCallRet TransitionFromReal16To32BitFlat
diff --git a/OvmfPkg/XenResetVector/XenResetVector.nasmb b/OvmfPkg/XenResetVector/XenResetVector.nasmb
index 49f2bab001..d5a791c139 100644
--- a/OvmfPkg/XenResetVector/XenResetVector.nasmb
+++ b/OvmfPkg/XenResetVector/XenResetVector.nasmb
@@ -70,6 +70,7 @@
 %include "Ia16/Init16.asm"
 
 %include "Main.asm"
+%include "Ia32/XenPVHMain.asm"
 
 %include "Ia16/ResetVectorVtf0.asm"
 
-- 
Anthony PERARD