diff --git a/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm b/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm
index 4bfa084c85..64e51d87ae 100644
--- a/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm
+++ b/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm
@@ -181,7 +181,7 @@ GetProcessorNumber:
 GetNextProcNumber:
     cmp         [edi], edx                       ; APIC ID match?
     jz          ProgramStack
-    add         edi, 16
+    add         edi, 20
     inc         ebx
     jmp         GetNextProcNumber    
 
diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c
index 3c2e6d6b89..15dbfa1e7d 100644
--- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
+++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
@@ -433,7 +433,7 @@ InitializeApData (
   IN OUT CPU_MP_DATA      *CpuMpData,
   IN     UINTN            ProcessorNumber,
   IN     UINT32           BistData,
-  IN     UINTN            ApTopOfStack
+  IN     UINT64           ApTopOfStack
   )
 {
   CPU_INFO_IN_HOB          *CpuInfoInHob;
@@ -442,7 +442,7 @@ InitializeApData (
   CpuInfoInHob[ProcessorNumber].InitialApicId = GetInitialApicId ();
   CpuInfoInHob[ProcessorNumber].ApicId        = GetApicId ();
   CpuInfoInHob[ProcessorNumber].Health        = BistData;
-  CpuInfoInHob[ProcessorNumber].ApTopOfStack  = (UINT32) ApTopOfStack;
+  CpuInfoInHob[ProcessorNumber].ApTopOfStack  = ApTopOfStack;
 
   CpuMpData->CpuData[ProcessorNumber].Waiting    = FALSE;
   CpuMpData->CpuData[ProcessorNumber].CpuHealthy = (BistData == 0) ? TRUE : FALSE;
@@ -480,7 +480,7 @@ ApWakeupFunction (
   UINT32                     BistData;
   volatile UINT32            *ApStartupSignalBuffer;
   CPU_INFO_IN_HOB            *CpuInfoInHob;
-  UINTN                      ApTopOfStack;
+  UINT64                     ApTopOfStack;
 
   //
   // AP finished assembly code and begin to execute C code
@@ -500,7 +500,7 @@ ApWakeupFunction (
       // This is first time AP wakeup, get BIST information from AP stack
       //
       ApTopOfStack  = CpuMpData->Buffer + (ProcessorNumber + 1) * CpuMpData->CpuApStackSize;
-      BistData = *(UINT32 *) (ApTopOfStack - sizeof (UINTN));
+      BistData = *(UINT32 *) ((UINTN) ApTopOfStack - sizeof (UINTN));
       //
       // Do some AP initialize sync
       //
diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.h b/UefiCpuPkg/Library/MpInitLib/MpLib.h
index 0ac777a099..f73a469ae8 100644
--- a/UefiCpuPkg/Library/MpInitLib/MpLib.h
+++ b/UefiCpuPkg/Library/MpInitLib/MpLib.h
@@ -129,12 +129,14 @@ typedef struct {
 // we need to make sure the each fields offset same in different
 // architecture.
 //
+#pragma pack (1)
 typedef struct {
   UINT32                         InitialApicId;
   UINT32                         ApicId;
   UINT32                         Health;
-  UINT32                         ApTopOfStack;
+  UINT64                         ApTopOfStack;
 } CPU_INFO_IN_HOB;
+#pragma pack ()
 
 //
 // AP reset code information including code address and size,
diff --git a/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm b/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
index 138b97312b..aaabb50c54 100644
--- a/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
+++ b/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
@@ -185,13 +185,12 @@ GetProcessorNumber:
 GetNextProcNumber:
     cmp         dword [edi], edx                      ; APIC ID match?
     jz          ProgramStack
-    add         edi, 16
+    add         edi, 20
     inc         ebx
     jmp         GetNextProcNumber    
 
 ProgramStack:
-    xor         rsp, rsp
-    mov         esp, dword [edi + 12]
+    mov         rsp, qword [edi + 12]
 
 CProcedureInvoke:
     push       rbp               ; Push BIST data at top of AP stack