[PATCH v2] UefiCpuPkg/MpInitLib: fix AP init issue in 64-bit PEI

[Jian J Wang <jian.j.wang@intel.com>]

> v2:
>    Roll back changes (just white spaces) caused by misoperation in git

This issue is introduced by a patch at

   f32bfe6d061420a15bac6083063d227c567e6388

The above patch miss the case of 64-bit PEI, which will link
X64/MpFuncs.nasm instead of Ia32/MpFuncs.nasm. For X64/MpFuncs.nasm,
ExchangeInfo->ModeHighMemory should be always initialized no matter
if separate wakeup buffer is allocated or not. Ia32/MpFuncs.nasm will
not need ModeHighMemory during AP init. So the changes made in this
patch should not affect the functionality of it.

Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
---
 UefiCpuPkg/Library/MpInitLib/MpLib.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c
index 42011d6231..0b7073fd02 100644
--- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
+++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
@@ -834,14 +834,15 @@ FillExchangeInfoData (
       );
 
     ExchangeInfo->ModeTransitionMemory = (UINT32)CpuMpData->WakeupBufferHigh;
-    ExchangeInfo->ModeHighMemory = (UINT32)CpuMpData->WakeupBufferHigh +
-                                   (UINT32)ExchangeInfo->ModeOffset -
-                                   (UINT32)CpuMpData->AddressMap.ModeTransitionOffset;
-    ExchangeInfo->ModeHighSegment = (UINT16)ExchangeInfo->CodeSegment;
   } else {
     ExchangeInfo->ModeTransitionMemory = (UINT32)
       (ExchangeInfo->BufferStart + CpuMpData->AddressMap.ModeTransitionOffset);
   }
+
+  ExchangeInfo->ModeHighMemory = ExchangeInfo->ModeTransitionMemory +
+                         (UINT32)ExchangeInfo->ModeOffset -
+                         (UINT32)CpuMpData->AddressMap.ModeTransitionOffset;
+  ExchangeInfo->ModeHighSegment = (UINT16)ExchangeInfo->CodeSegment;
 }
 
 /**
-- 
2.15.1.windows.2