50 files changed, 147 insertions, 141 deletions
diff --git a/MdePkg/Library/BaseLib/X64/DisablePaging64.asm b/MdePkg/Library/BaseLib/X64/DisablePaging64.asm
index 7b1e1b8bd2..2609c941aa 100644
--- a/MdePkg/Library/BaseLib/X64/DisablePaging64.asm
+++ b/MdePkg/Library/BaseLib/X64/DisablePaging64.asm
@@ -23,6 +23,17 @@
 
     .code
 
+;------------------------------------------------------------------------------
+; VOID
+; EFIAPI
+; InternalX86DisablePaging64 (
+;   IN      UINT16                    Cs,
+;   IN      UINT32                    EntryPoint,
+;   IN      UINT32                    Context1,  OPTIONAL
+;   IN      UINT32                    Context2,  OPTIONAL
+;   IN      UINT32                    NewStack
+;   );
+;------------------------------------------------------------------------------
 InternalX86DisablePaging64    PROC
     cli
     shl     rcx, 32
diff --git a/MdePkg/Library/BaseLib/X64/FxRestore.asm b/MdePkg/Library/BaseLib/X64/FxRestore.asm
index 8acfc2f00f..7e7037e9e6 100644
--- a/MdePkg/Library/BaseLib/X64/FxRestore.asm
+++ b/MdePkg/Library/BaseLib/X64/FxRestore.asm
@@ -23,6 +23,13 @@
 
     .code
 
+;------------------------------------------------------------------------------
+; VOID
+; EFIAPI
+; InternalX86FxRestore (
+;   IN CONST IA32_FX_BUFFER *Buffer
+;   );
+;------------------------------------------------------------------------------
 InternalX86FxRestore  PROC
     fxrstor [rcx]
     ret
diff --git a/MdePkg/Library/BaseLib/X64/FxSave.asm b/MdePkg/Library/BaseLib/X64/FxSave.asm
index cacb1f5283..ea19cd1648 100644
--- a/MdePkg/Library/BaseLib/X64/FxSave.asm
+++ b/MdePkg/Library/BaseLib/X64/FxSave.asm
@@ -23,6 +23,13 @@
 
     .code
 
+;------------------------------------------------------------------------------
+; VOID
+; EFIAPI
+; InternalX86FxSave (
+;   OUT IA32_FX_BUFFER *Buffer
+;   );
+;------------------------------------------------------------------------------
 InternalX86FxSave PROC
     fxsave  [rcx]
     ret
diff --git a/MdePkg/Library/BaseLib/X64/LongJump.asm b/MdePkg/Library/BaseLib/X64/LongJump.asm
index fb6378d030..6ef5f964e0 100644
--- a/MdePkg/Library/BaseLib/X64/LongJump.asm
+++ b/MdePkg/Library/BaseLib/X64/LongJump.asm
@@ -21,6 +21,14 @@
 
     .code
 
+;------------------------------------------------------------------------------
+; VOID
+; EFIAPI
+; InternalLongJump (
+;   IN      BASE_LIBRARY_JUMP_BUFFER  *JumpBuffer,
+;   IN      UINTN                     Value
+;   );
+;------------------------------------------------------------------------------
 InternalLongJump    PROC
     mov     rbx, [rcx]
     mov     rsp, [rcx + 8]
diff --git a/MdePkg/Library/BaseLib/X64/ReadCs.asm b/MdePkg/Library/BaseLib/X64/ReadCs.asm
index 126149a47c..642ce5b169 100644
--- a/MdePkg/Library/BaseLib/X64/ReadCs.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadCs.asm
@@ -31,7 +31,7 @@
 ;   );
 ;------------------------------------------------------------------------------
 AsmReadCs   PROC
-    mov     ax, cs
+    mov     eax, cs
     ret
 AsmReadCs   ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/ReadDs.asm b/MdePkg/Library/BaseLib/X64/ReadDs.asm
index bdcddb65d8..6f2629872b 100644
--- a/MdePkg/Library/BaseLib/X64/ReadDs.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadDs.asm
@@ -31,9 +31,8 @@
 ;   );
 ;------------------------------------------------------------------------------
 AsmReadDs   PROC
-    mov     ax, ds
+    mov     eax, ds
     ret
 AsmReadDs   ENDP
 
     END
-
diff --git a/MdePkg/Library/BaseLib/X64/ReadEs.asm b/MdePkg/Library/BaseLib/X64/ReadEs.asm
index 40384bcd71..d5fe84d73f 100644
--- a/MdePkg/Library/BaseLib/X64/ReadEs.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadEs.asm
@@ -31,7 +31,7 @@
 ;   );
 ;------------------------------------------------------------------------------
 AsmReadEs   PROC
-    mov     ax, es
+    mov     eax, es
     ret
 AsmReadEs   ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/ReadFs.asm b/MdePkg/Library/BaseLib/X64/ReadFs.asm
index b63e474023..d44ee545af 100644
--- a/MdePkg/Library/BaseLib/X64/ReadFs.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadFs.asm
@@ -31,7 +31,7 @@
 ;   );
 ;------------------------------------------------------------------------------
 AsmReadFs   PROC
-    mov     ax, fs
+    mov     eax, fs
     ret
 AsmReadFs   ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/ReadGdtr.asm b/MdePkg/Library/BaseLib/X64/ReadGdtr.asm
index 2d40599a8b..0bc2949b54 100644
--- a/MdePkg/Library/BaseLib/X64/ReadGdtr.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadGdtr.asm
@@ -23,6 +23,13 @@
 
     .code
 
+;------------------------------------------------------------------------------
+; VOID
+; EFIAPI
+; InternalX86ReadGdtr (
+;   OUT IA32_DESCRIPTOR  *Gdtr
+;   );
+;------------------------------------------------------------------------------
 InternalX86ReadGdtr   PROC
     sgdt    fword ptr [rcx]
     ret
diff --git a/MdePkg/Library/BaseLib/X64/ReadGs.asm b/MdePkg/Library/BaseLib/X64/ReadGs.asm
index 02d140e670..bc5de7691b 100644
--- a/MdePkg/Library/BaseLib/X64/ReadGs.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadGs.asm
@@ -31,7 +31,7 @@
 ;   );
 ;------------------------------------------------------------------------------
 AsmReadGs   PROC
-    mov     ax, gs
+    mov     eax, gs
     ret
 AsmReadGs   ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/ReadIdtr.asm b/MdePkg/Library/BaseLib/X64/ReadIdtr.asm
index 260f697178..db684f3671 100644
--- a/MdePkg/Library/BaseLib/X64/ReadIdtr.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadIdtr.asm
@@ -23,6 +23,13 @@
 
     .code
 
+;------------------------------------------------------------------------------
+; VOID
+; EFIAPI
+; InternalX86ReadIdtr (
+;   OUT     IA32_DESCRIPTOR           *Idtr
+;   );
+;------------------------------------------------------------------------------
 InternalX86ReadIdtr   PROC
     sidt    fword ptr [rcx]
     ret
diff --git a/MdePkg/Library/BaseLib/X64/ReadMm0.asm b/MdePkg/Library/BaseLib/X64/ReadMm0.asm
index 1239bcacd6..a81d208298 100644
--- a/MdePkg/Library/BaseLib/X64/ReadMm0.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadMm0.asm
@@ -24,7 +24,7 @@
     .code
 
 ;------------------------------------------------------------------------------
-; UINTN
+; UINT64
 ; EFIAPI
 ; AsmReadMm0 (
 ;   VOID
diff --git a/MdePkg/Library/BaseLib/X64/ReadMm1.asm b/MdePkg/Library/BaseLib/X64/ReadMm1.asm
index b42bd7f63f..5da8c4f9e5 100644
--- a/MdePkg/Library/BaseLib/X64/ReadMm1.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadMm1.asm
@@ -24,7 +24,7 @@
     .code
 
 ;------------------------------------------------------------------------------
-; UINTN
+; UINT64
 ; EFIAPI
 ; AsmReadMm1 (
 ;   VOID
diff --git a/MdePkg/Library/BaseLib/X64/ReadMm2.asm b/MdePkg/Library/BaseLib/X64/ReadMm2.asm
index b10782e403..3b2b1e3af3 100644
--- a/MdePkg/Library/BaseLib/X64/ReadMm2.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadMm2.asm
@@ -24,7 +24,7 @@
     .code
 
 ;------------------------------------------------------------------------------
-; UINTN
+; UINT64
 ; EFIAPI
 ; AsmReadMm2 (
 ;   VOID
diff --git a/MdePkg/Library/BaseLib/X64/ReadMm3.asm b/MdePkg/Library/BaseLib/X64/ReadMm3.asm
index 15a96475bd..6283c30285 100644
--- a/MdePkg/Library/BaseLib/X64/ReadMm3.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadMm3.asm
@@ -24,7 +24,7 @@
     .code
 
 ;------------------------------------------------------------------------------
-; UINTN
+; UINT64
 ; EFIAPI
 ; AsmReadMm3 (
 ;   VOID
diff --git a/MdePkg/Library/BaseLib/X64/ReadMm4.asm b/MdePkg/Library/BaseLib/X64/ReadMm4.asm
index 73f528342e..a65f130283 100644
--- a/MdePkg/Library/BaseLib/X64/ReadMm4.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadMm4.asm
@@ -24,7 +24,7 @@
     .code
 
 ;------------------------------------------------------------------------------
-; UINTN
+; UINT64
 ; EFIAPI
 ; AsmReadMm4 (
 ;   VOID
diff --git a/MdePkg/Library/BaseLib/X64/ReadMm5.asm b/MdePkg/Library/BaseLib/X64/ReadMm5.asm
index a487889480..5295c38ae0 100644
--- a/MdePkg/Library/BaseLib/X64/ReadMm5.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadMm5.asm
@@ -24,7 +24,7 @@
     .code
 
 ;------------------------------------------------------------------------------
-; UINTN
+; UINT64
 ; EFIAPI
 ; AsmReadMm5 (
 ;   VOID
diff --git a/MdePkg/Library/BaseLib/X64/ReadMm6.asm b/MdePkg/Library/BaseLib/X64/ReadMm6.asm
index 56f81bf7b1..acdc99b888 100644
--- a/MdePkg/Library/BaseLib/X64/ReadMm6.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadMm6.asm
@@ -24,7 +24,7 @@
     .code
 
 ;------------------------------------------------------------------------------
-; UINTN
+; UINT64
 ; EFIAPI
 ; AsmReadMm6 (
 ;   VOID
diff --git a/MdePkg/Library/BaseLib/X64/ReadMm7.asm b/MdePkg/Library/BaseLib/X64/ReadMm7.asm
index e3ad6bb658..7a1b4e6111 100644
--- a/MdePkg/Library/BaseLib/X64/ReadMm7.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadMm7.asm
@@ -24,7 +24,7 @@
     .code
 
 ;------------------------------------------------------------------------------
-; UINTN
+; UINT64
 ; EFIAPI
 ; AsmReadMm7 (
 ;   VOID
diff --git a/MdePkg/Library/BaseLib/X64/ReadMsr32.asm b/MdePkg/Library/BaseLib/X64/ReadMsr32.asm
deleted file mode 100644
index 271eabbeae..0000000000
--- a/MdePkg/Library/BaseLib/X64/ReadMsr32.asm
+++ /dev/null
@@ -1,38 +0,0 @@
-;------------------------------------------------------------------------------
-;
-; Copyright (c) 2006, Intel Corporation
-; All rights reserved. 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.
-;
-; Module Name:
-;
-;   ReadMsr32.Asm
-;
-; Abstract:
-;
-;   AsmReadMsr32 function
-;
-; Notes:
-;
-;------------------------------------------------------------------------------
-
-    .code
-
-;------------------------------------------------------------------------------
-; UINT32
-; EFIAPI
-; AsmReadMsr32 (
-;   IN UINT32  Index
-;   );
-;------------------------------------------------------------------------------
-AsmReadMsr32    PROC
-    rdmsr
-    ret
-AsmReadMsr32    ENDP
-
-    END
diff --git a/MdePkg/Library/BaseLib/X64/ReadMsr64.asm b/MdePkg/Library/BaseLib/X64/ReadMsr64.asm
index 4444c18676..580c0761a4 100644
--- a/MdePkg/Library/BaseLib/X64/ReadMsr64.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadMsr64.asm
@@ -31,9 +31,9 @@
 ;   );
 ;------------------------------------------------------------------------------
 AsmReadMsr64    PROC
-    rdmsr
-    shl     rax, 20h
-    shrd    rax, rdx, 20h
+    rdmsr                               ; edx & eax are zero extended
+    shl     rdx, 20h
+    or      rax, rdx
     ret
 AsmReadMsr64    ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/ReadPmc.asm b/MdePkg/Library/BaseLib/X64/ReadPmc.asm
index b5004d6f34..5ca60fa85f 100644
--- a/MdePkg/Library/BaseLib/X64/ReadPmc.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadPmc.asm
@@ -32,11 +32,8 @@
 ;------------------------------------------------------------------------------
 AsmReadPmc  PROC
     rdpmc
-    shl     ecx, 1
-    jnc     @F
-    shl     rax, 20h
-    shrd    rax, rdx, 20h
-@@:
+    shl     rdx, 20h
+    or      rax, rdx
     ret
 AsmReadPmc  ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/ReadSs.asm b/MdePkg/Library/BaseLib/X64/ReadSs.asm
index 4aa480d71b..2c2be564ac 100644
--- a/MdePkg/Library/BaseLib/X64/ReadSs.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadSs.asm
@@ -31,7 +31,7 @@
 ;   );
 ;------------------------------------------------------------------------------
 AsmReadSs   PROC
-    mov     ax, ss
+    mov     eax, ss
     ret
 AsmReadSs   ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/ReadTsc.asm b/MdePkg/Library/BaseLib/X64/ReadTsc.asm
index 25fa2cc5d8..7c45eebd54 100644
--- a/MdePkg/Library/BaseLib/X64/ReadTsc.asm
+++ b/MdePkg/Library/BaseLib/X64/ReadTsc.asm
@@ -32,8 +32,8 @@
 ;------------------------------------------------------------------------------
 AsmReadTsc  PROC
     rdtsc
-    shl     rax, 20h
-    shrd    rax, rdx, 20h
+    shl     rdx, 20h
+    or      rax, rdx
     ret
 AsmReadTsc  ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/SetJump.asm b/MdePkg/Library/BaseLib/X64/SetJump.asm
index 148b0cb65e..2ed581ea9d 100644
--- a/MdePkg/Library/BaseLib/X64/SetJump.asm
+++ b/MdePkg/Library/BaseLib/X64/SetJump.asm
@@ -23,6 +23,13 @@
 
 EXTERNDEF   InternalAssertJumpBuffer:PROC
 
+;------------------------------------------------------------------------------
+; UINTN
+; EFIAPI
+; SetJump (
+;   OUT     BASE_LIBRARY_JUMP_BUFFER  *JumpBuffer
+;   );
+;------------------------------------------------------------------------------
 SetJump     PROC
     push    rcx
     add     rsp, -20h
diff --git a/MdePkg/Library/BaseLib/X64/Thunk16.asm b/MdePkg/Library/BaseLib/X64/Thunk16.asm
index b120434efb..2c35c72a57 100644
--- a/MdePkg/Library/BaseLib/X64/Thunk16.asm
+++ b/MdePkg/Library/BaseLib/X64/Thunk16.asm
@@ -61,6 +61,10 @@ SavedGdt    LABEL   FWORD
             DW      ?
             DQ      ?
 
+;------------------------------------------------------------------------------
+; _BackFromUserCode() takes control in real mode after 'retf' has been executed
+; by user code. It will be shadowed to somewhere in memory below 1MB.
+;------------------------------------------------------------------------------
 _BackFromUserCode   PROC
     DB      16h                         ; push ss
     DB      0eh                         ; push cs
@@ -125,6 +129,10 @@ _16Gdtr     LABEL   FWORD
 _16GdtrBase DQ      _NullSegDesc
 _16Idtr     FWORD   (1 SHL 10) - 1
 
+;------------------------------------------------------------------------------
+; _ToUserCode() takes control in real mode before passing control to user code.
+; It will be shadowed to somewhere in memory below 1MB.
+;------------------------------------------------------------------------------
 _ToUserCode PROC
     mov     edi, ss
     mov     ss, edx                     ; set new segment selectors
@@ -184,11 +192,14 @@ _16DsDesc       LABEL   QWORD
                 DB      0
 GdtEnd          LABEL   QWORD
 
-;
-;   @param  RegSet  Pointer to a IA32_DWORD_REGS structure
-;   @param  Transition  Pointer to the transition code
-;   @return The address of the 16-bit stack after returning from user code
-;
+;------------------------------------------------------------------------------
+; IA32_REGISTER_SET *
+; EFIAPI
+; InternalAsmThunk16 (
+;   IN      IA32_REGISTER_SET         *RegisterSet,
+;   IN OUT  VOID                      *Transition
+;   );
+;------------------------------------------------------------------------------
 InternalAsmThunk16  PROC    USES    rbp rbx rsi rdi
     mov     r10d, ds
     mov     r11d, es
diff --git a/MdePkg/Library/BaseLib/X64/WriteCr0.asm b/MdePkg/Library/BaseLib/X64/WriteCr0.asm
index defc7e7c96..caf1904d2e 100644
--- a/MdePkg/Library/BaseLib/X64/WriteCr0.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteCr0.asm
@@ -27,11 +27,12 @@
 ; UINTN
 ; EFIAPI
 ; AsmWriteCr0 (
-;   VOID
+;   UINTN  Cr0
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteCr0 PROC
     mov     cr0, rcx
+    mov     rax, rcx
     ret
 AsmWriteCr0 ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/WriteCr2.asm b/MdePkg/Library/BaseLib/X64/WriteCr2.asm
index ebe6f89d62..ee5b546262 100644
--- a/MdePkg/Library/BaseLib/X64/WriteCr2.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteCr2.asm
@@ -27,11 +27,12 @@
 ; UINTN
 ; EFIAPI
 ; AsmWriteCr2 (
-;   VOID
+;   UINTN  Cr2
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteCr2 PROC
     mov     cr2, rcx
+    mov     rax, rcx
     ret
 AsmWriteCr2 ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/WriteCr3.asm b/MdePkg/Library/BaseLib/X64/WriteCr3.asm
index 5715dea9b7..e63229820e 100644
--- a/MdePkg/Library/BaseLib/X64/WriteCr3.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteCr3.asm
@@ -27,11 +27,12 @@
 ; UINTN
 ; EFIAPI
 ; AsmWriteCr3 (
-;   VOID
+;   UINTN  Cr3
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteCr3 PROC
     mov     cr3, rcx
+    mov     rax, rcx
     ret
 AsmWriteCr3 ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/WriteCr4.asm b/MdePkg/Library/BaseLib/X64/WriteCr4.asm
index 210744e16f..3e79fe23e4 100644
--- a/MdePkg/Library/BaseLib/X64/WriteCr4.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteCr4.asm
@@ -27,11 +27,12 @@
 ; UINTN
 ; EFIAPI
 ; AsmWriteCr4 (
-;   VOID
+;   UINTN  Cr4
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteCr4 PROC
     mov     cr4, rcx
+    mov     rax, rcx
     ret
 AsmWriteCr4 ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/WriteDr0.asm b/MdePkg/Library/BaseLib/X64/WriteDr0.asm
index 2515a20404..a1131fead9 100644
--- a/MdePkg/Library/BaseLib/X64/WriteDr0.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteDr0.asm
@@ -27,11 +27,12 @@
 ; UINTN
 ; EFIAPI
 ; AsmWriteDr0 (
-;   VOID
+;   IN UINTN Value
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteDr0 PROC
     mov     dr0, rcx
+    mov     rax, rcx
     ret
 AsmWriteDr0 ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/WriteDr1.asm b/MdePkg/Library/BaseLib/X64/WriteDr1.asm
index 89f36ac3f9..366edb6ef8 100644
--- a/MdePkg/Library/BaseLib/X64/WriteDr1.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteDr1.asm
@@ -27,11 +27,12 @@
 ; UINTN
 ; EFIAPI
 ; AsmWriteDr1 (
-;   VOID
+;   IN UINTN Value
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteDr1 PROC
     mov     dr1, rcx
+    mov     rax, rcx
     ret
 AsmWriteDr1 ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/WriteDr2.asm b/MdePkg/Library/BaseLib/X64/WriteDr2.asm
index 820977c2e4..bde8e3d929 100644
--- a/MdePkg/Library/BaseLib/X64/WriteDr2.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteDr2.asm
@@ -27,11 +27,12 @@
 ; UINTN
 ; EFIAPI
 ; AsmWriteDr2 (
-;   VOID
+;   IN UINTN Value
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteDr2 PROC
     mov     dr2, rcx
+    mov     rax, rcx
     ret
 AsmWriteDr2 ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/WriteDr3.asm b/MdePkg/Library/BaseLib/X64/WriteDr3.asm
index 51c1407277..65180a27d5 100644
--- a/MdePkg/Library/BaseLib/X64/WriteDr3.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteDr3.asm
@@ -27,11 +27,12 @@
 ; UINTN
 ; EFIAPI
 ; AsmWriteDr3 (
-;   VOID
+;   IN UINTN Value
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteDr3 PROC
     mov     dr3, rcx
+    mov     rax, rcx
     ret
 AsmWriteDr3 ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/WriteDr4.asm b/MdePkg/Library/BaseLib/X64/WriteDr4.asm
index 12b643825b..ad618f1089 100644
--- a/MdePkg/Library/BaseLib/X64/WriteDr4.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteDr4.asm
@@ -27,11 +27,12 @@
 ; UINTN
 ; EFIAPI
 ; AsmWriteDr4 (
-;   VOID
+;   IN UINTN Value
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteDr4 PROC
     DB      0fh, 23h, 0e1h
+    mov     rax, rcx
     ret
 AsmWriteDr4 ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/WriteDr5.asm b/MdePkg/Library/BaseLib/X64/WriteDr5.asm
index 6d454d5267..91eeef20e3 100644
--- a/MdePkg/Library/BaseLib/X64/WriteDr5.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteDr5.asm
@@ -26,12 +26,13 @@
 ;------------------------------------------------------------------------------
 ; UINTN
 ; EFIAPI
-; AsmWriteDr5 (
-;   VOID
+; AsmWriteDr6 (
+;   IN UINTN Value
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteDr5 PROC
     DB      0fh, 23h, 0e9h
+    mov     rax, rcx
     ret
 AsmWriteDr5 ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/WriteDr6.asm b/MdePkg/Library/BaseLib/X64/WriteDr6.asm
index b7b9f2509d..f1ddae8bfc 100644
--- a/MdePkg/Library/BaseLib/X64/WriteDr6.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteDr6.asm
@@ -27,11 +27,12 @@
 ; UINTN
 ; EFIAPI
 ; AsmWriteDr6 (
-;   VOID
+;   IN UINTN Value
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteDr6 PROC
     mov     dr6, rcx
+    mov     rax, rcx
     ret
 AsmWriteDr6 ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/WriteDr7.asm b/MdePkg/Library/BaseLib/X64/WriteDr7.asm
index de2237b6e4..6a0cbfa6ff 100644
--- a/MdePkg/Library/BaseLib/X64/WriteDr7.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteDr7.asm
@@ -27,11 +27,12 @@
 ; UINTN
 ; EFIAPI
 ; AsmWriteDr7 (
-;   VOID
+;   IN UINTN Value
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteDr7 PROC
     mov     dr7, rcx
+    mov     rax, rcx
     ret
 AsmWriteDr7 ENDP
 
diff --git a/MdePkg/Library/BaseLib/X64/WriteGdtr.asm b/MdePkg/Library/BaseLib/X64/WriteGdtr.asm
index 1757e3dea4..fa99a499e7 100644
--- a/MdePkg/Library/BaseLib/X64/WriteGdtr.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteGdtr.asm
@@ -23,6 +23,13 @@
 
     .code
 
+;------------------------------------------------------------------------------
+; VOID
+; EFIAPI
+; InternalX86WriteGdtr (
+;   IN      CONST IA32_DESCRIPTOR     *Idtr
+;   );
+;------------------------------------------------------------------------------
 InternalX86WriteGdtr  PROC
     lgdt    fword ptr [rcx]
     ret
diff --git a/MdePkg/Library/BaseLib/X64/WriteIdtr.asm b/MdePkg/Library/BaseLib/X64/WriteIdtr.asm
index 09fcb9e457..2f6c081ab6 100644
--- a/MdePkg/Library/BaseLib/X64/WriteIdtr.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteIdtr.asm
@@ -23,6 +23,13 @@
 
     .code
 
+;------------------------------------------------------------------------------
+; VOID
+; EFIAPI
+; InternalX86WriteIdtr (
+;   IN      CONST IA32_DESCRIPTOR     *Idtr
+;   );
+;------------------------------------------------------------------------------
 InternalX86WriteIdtr  PROC
     lidt    fword ptr [rcx]
     ret
diff --git a/MdePkg/Library/BaseLib/X64/WriteMm0.asm b/MdePkg/Library/BaseLib/X64/WriteMm0.asm
index bb9a576125..0ad65e366d 100644
--- a/MdePkg/Library/BaseLib/X64/WriteMm0.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteMm0.asm
@@ -24,10 +24,10 @@
     .code
 
 ;------------------------------------------------------------------------------
-; UINTN
+; VOID
 ; EFIAPI
 ; AsmWriteMm0 (
-;   VOID
+;   IN UINT64   Value
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteMm0 PROC
diff --git a/MdePkg/Library/BaseLib/X64/WriteMm1.asm b/MdePkg/Library/BaseLib/X64/WriteMm1.asm
index 1bab3bcd8e..66425a43c2 100644
--- a/MdePkg/Library/BaseLib/X64/WriteMm1.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteMm1.asm
@@ -24,10 +24,10 @@
     .code
 
 ;------------------------------------------------------------------------------
-; UINTN
+; VOID
 ; EFIAPI
 ; AsmWriteMm1 (
-;   VOID
+;   IN UINT64   Value
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteMm1 PROC
diff --git a/MdePkg/Library/BaseLib/X64/WriteMm2.asm b/MdePkg/Library/BaseLib/X64/WriteMm2.asm
index 97e8a6a676..bd0f0a0e1a 100644
--- a/MdePkg/Library/BaseLib/X64/WriteMm2.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteMm2.asm
@@ -24,10 +24,10 @@
     .code
 
 ;------------------------------------------------------------------------------
-; UINTN
+; VOID
 ; EFIAPI
 ; AsmWriteMm2 (
-;   VOID
+;   IN UINT64   Value
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteMm2 PROC
diff --git a/MdePkg/Library/BaseLib/X64/WriteMm3.asm b/MdePkg/Library/BaseLib/X64/WriteMm3.asm
index d55e19a406..fa36ea64bb 100644
--- a/MdePkg/Library/BaseLib/X64/WriteMm3.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteMm3.asm
@@ -24,10 +24,10 @@
     .code
 
 ;------------------------------------------------------------------------------
-; UINTN
+; VOID
 ; EFIAPI
 ; AsmWriteMm3 (
-;   VOID
+;   IN UINT64   Value
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteMm3 PROC
diff --git a/MdePkg/Library/BaseLib/X64/WriteMm4.asm b/MdePkg/Library/BaseLib/X64/WriteMm4.asm
index 2a69b93bcc..d9bc46e16c 100644
--- a/MdePkg/Library/BaseLib/X64/WriteMm4.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteMm4.asm
@@ -24,10 +24,10 @@
     .code
 
 ;------------------------------------------------------------------------------
-; UINTN
+; VOID
 ; EFIAPI
 ; AsmWriteMm4 (
-;   VOID
+;   IN UINT64   Value
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteMm4 PROC
diff --git a/MdePkg/Library/BaseLib/X64/WriteMm5.asm b/MdePkg/Library/BaseLib/X64/WriteMm5.asm
index c4d798bcbd..f268bea8ec 100644
--- a/MdePkg/Library/BaseLib/X64/WriteMm5.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteMm5.asm
@@ -24,10 +24,10 @@
     .code
 
 ;------------------------------------------------------------------------------
-; UINTN
+; VOID
 ; EFIAPI
 ; AsmWriteMm5 (
-;   VOID
+;   IN UINT64   Value
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteMm5 PROC
diff --git a/MdePkg/Library/BaseLib/X64/WriteMm6.asm b/MdePkg/Library/BaseLib/X64/WriteMm6.asm
index c0164f66da..cb32ea6dc3 100644
--- a/MdePkg/Library/BaseLib/X64/WriteMm6.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteMm6.asm
@@ -24,10 +24,10 @@
     .code
 
 ;------------------------------------------------------------------------------
-; UINTN
+; VOID
 ; EFIAPI
 ; AsmWriteMm6 (
-;   VOID
+;   IN UINT64   Value
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteMm6 PROC
diff --git a/MdePkg/Library/BaseLib/X64/WriteMm7.asm b/MdePkg/Library/BaseLib/X64/WriteMm7.asm
index 20768e2b78..f5713823bb 100644
--- a/MdePkg/Library/BaseLib/X64/WriteMm7.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteMm7.asm
@@ -24,10 +24,10 @@
     .code
 
 ;------------------------------------------------------------------------------
-; UINTN
+; VOID
 ; EFIAPI
 ; AsmWriteMm7 (
-;   VOID
+;   IN UINT64   Value
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteMm7 PROC
diff --git a/MdePkg/Library/BaseLib/X64/WriteMsr32.asm b/MdePkg/Library/BaseLib/X64/WriteMsr32.asm
deleted file mode 100644
index 0a74403624..0000000000
--- a/MdePkg/Library/BaseLib/X64/WriteMsr32.asm
+++ /dev/null
@@ -1,41 +0,0 @@
-;------------------------------------------------------------------------------
-;
-; Copyright (c) 2006, Intel Corporation
-; All rights reserved. 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.
-;
-; Module Name:
-;
-;   WriteMsr32.Asm
-;
-; Abstract:
-;
-;   AsmWriteMsr32 function
-;
-; Notes:
-;
-;------------------------------------------------------------------------------
-
-    .code
-
-;------------------------------------------------------------------------------
-; UINT32
-; EFIAPI
-; AsmWriteMsr32 (
-;   IN UINT32  Index,
-;   IN UINT32  Value
-;   );
-;------------------------------------------------------------------------------
-AsmWriteMsr32   PROC
-    mov     eax, edx
-    xor     edx, edx
-    wrmsr
-    ret
-AsmWriteMsr32   ENDP
-
-    END
diff --git a/MdePkg/Library/BaseLib/X64/WriteMsr64.asm b/MdePkg/Library/BaseLib/X64/WriteMsr64.asm
index 3337f45891..6b8066f922 100644
--- a/MdePkg/Library/BaseLib/X64/WriteMsr64.asm
+++ b/MdePkg/Library/BaseLib/X64/WriteMsr64.asm
@@ -32,11 +32,9 @@
 ;   );
 ;------------------------------------------------------------------------------
 AsmWriteMsr64   PROC
-    push    rdx
-    mov     eax, edx
+    mov     rax, rdx
     shr     rdx, 20h
     wrmsr
-    pop     rax
     ret
 AsmWriteMsr64   ENDP