From d603b1151c3b6d6961c65693063f16bb71a3c91c Mon Sep 17 00:00:00 2001
From: Jeff Fan <jeff.fan@intel.com>
Date: Fri, 18 Dec 2015 03:22:56 +0000
Subject: [PATCH] UefiCpuPkg/CpuMpPei: Fix pack(1) issue on x64 arch

Packing alignment for MP_CPU_EXCHANGE_INFO should be 1. This should be typo when
check-in CpuMpPei driver. IA32 arch MP_CPU_EXCHANGE_INFO is luckly pack(1). It
leads CpuMpPei x64 version hung.

Contributed-under: TianoCore Contribution Agreement 1.0
Reported-by: Michael Kinney <michael.d.kinney@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Tested-by: Michael Kinney <michael.d.kinney@intel.com>
Reviewed-by: Michael Kinney <michael.d.kinney@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19340 6f19259b-4bc3-4df7-8a09-765794883524
---
 UefiCpuPkg/CpuMpPei/CpuMpPei.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/UefiCpuPkg/CpuMpPei/CpuMpPei.h b/UefiCpuPkg/CpuMpPei/CpuMpPei.h
index f2286b990e..2b960c6eb1 100644
--- a/UefiCpuPkg/CpuMpPei/CpuMpPei.h
+++ b/UefiCpuPkg/CpuMpPei/CpuMpPei.h
@@ -72,7 +72,7 @@ typedef struct {
 
 typedef struct _PEI_CPU_MP_DATA  PEI_CPU_MP_DATA;
 
-#pragma pack()
+#pragma pack(1)
 
 typedef union {
   struct {
@@ -95,6 +95,8 @@ typedef union {
 
 //
 // MP CPU exchange information for AP reset code
+// This structure is required to be packed because fixed field offsets
+// into this structure are used in assembly code in this module
 //
 typedef struct {
   UINTN                 Lock;
-- 
2.39.2