diff --git a/MdePkg/Include/Library/BaseLib.h b/MdePkg/Include/Library/BaseLib.h
index c79b7a9a2f..d704e98f5f 100644
--- a/MdePkg/Include/Library/BaseLib.h
+++ b/MdePkg/Include/Library/BaseLib.h
@@ -7006,7 +7006,7 @@ AsmDisablePaging64 (
   in ExtraStackSize. If parameters are passed to the 16-bit real mode code,
   then the actual minimum stack size is ExtraStackSize plus the maximum number
   of bytes that need to be passed to the 16-bit real mode code.
-
+  
   If RealModeBufferSize is NULL, then ASSERT().
   If ExtraStackSize is NULL, then ASSERT().
 
@@ -7030,6 +7030,9 @@ AsmGetThunk16Properties (
   Prepares all structures a code required to use AsmThunk16().
 
   Prepares all structures and code required to use AsmThunk16().
+  
+  This interface is limited to be used in physical mode but can not be used in 
+  virtual mode with paging.
 
   If ThunkContext is NULL, then ASSERT().
 
@@ -7090,6 +7093,9 @@ AsmPrepareThunk16 (
   If both THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 and THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL are set in 
   ThunkAttributes, then ASSERT().
 
+  This interface is limited to be used in physical mode but can not be used in 
+  virtual mode with paging.
+
   @param  ThunkContext  A pointer to the context structure that describes the
                         16-bit real mode code to call.
 
@@ -7112,6 +7118,9 @@ AsmThunk16 (
   real mode thunk, then it is more efficient if AsmPrepareThunk16() is called
   once and AsmThunk16() can be called for each 16-bit real mode thunk.
 
+  This interface is limited to be used in physical mode but can not be used in 
+  virtual mode with paging.
+
   See AsmPrepareThunk16() and AsmThunk16() for the detailed description and ASSERT() conditions.
 
   @param  ThunkContext  A pointer to the context structure that describes the
diff --git a/MdePkg/Library/BaseLib/X86Thunk.c b/MdePkg/Library/BaseLib/X86Thunk.c
index fbd198984d..72c918756d 100644
--- a/MdePkg/Library/BaseLib/X86Thunk.c
+++ b/MdePkg/Library/BaseLib/X86Thunk.c
@@ -109,6 +109,9 @@ AsmGetThunk16Properties (
   Prepares all structures a code required to use AsmThunk16().
 
   Prepares all structures and code required to use AsmThunk16().
+  
+  This interface is limited to be used in physical mode but can not be used in 
+  virtual mode with paging.
 
   If ThunkContext is NULL, then ASSERT().
 
@@ -227,6 +230,9 @@ AsmPrepareThunk16 (
   If both THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 and THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL are set in 
   ThunkAttributes, then ASSERT().
 
+  This interface is limited to be used in physical mode but can not be used in 
+  virtual mode with paging.
+  
   @param  ThunkContext  A pointer to the context structure that describes the
                         16-bit real mode code to call.
 
@@ -263,6 +269,9 @@ AsmThunk16 (
   real mode thunk, then it is more efficient if AsmPrepareThunk16() is called
   once and AsmThunk16() can be called for each 16-bit real mode thunk.
 
+  This interface is limited to be used in physical mode but can not be used in 
+  virtual mode with paging.
+  
   See AsmPrepareThunk16() and AsmThunk16() for the detailed description and ASSERT() conditions.
 
   @param  ThunkContext  A pointer to the context structure that describes the