diff --git a/MdeModulePkg/Core/PiSmmCore/PiSmmIpl.c b/MdeModulePkg/Core/PiSmmCore/PiSmmIpl.c
index 31d2c9e45e..a7663ca291 100644
--- a/MdeModulePkg/Core/PiSmmCore/PiSmmIpl.c
+++ b/MdeModulePkg/Core/PiSmmCore/PiSmmIpl.c
@@ -90,20 +90,30 @@ SmmBase2GetSmstLocation (
   be called in physical mode prior to SetVirtualAddressMap() and in virtual mode 
   after SetVirtualAddressMap().
 
-  @param[in]     This                The EFI_SMM_COMMUNICATION_PROTOCOL instance.
-  @param[in, out] CommBuffer          A pointer to the buffer to convey into SMRAM.
-  @param[in, out] CommSize            The size of the data buffer being passed in.On exit, the size of data
-                                     being returned. Zero if the handler does not wish to reply with any data.
+  @param[in] This                The EFI_SMM_COMMUNICATION_PROTOCOL instance.
+  @param[in, out] CommBuffer     A pointer to the buffer to convey into SMRAM.
+  @param[in, out] CommSize       The size of the data buffer being passed in. On exit, the size of data
+                                 being returned. Zero if the handler does not wish to reply with any data.
+                                 This parameter is optional and may be NULL.
+
+  @retval EFI_SUCCESS            The message was successfully posted.
+  @retval EFI_INVALID_PARAMETER  The CommBuffer was NULL.
+  @retval EFI_BAD_BUFFER_SIZE    The buffer is too large for the MM implementation.
+                                 If this error is returned, the MessageLength field
+                                 in the CommBuffer header or the integer pointed by
+                                 CommSize, are updated to reflect the maximum payload
+                                 size the implementation can accommodate.
+  @retval EFI_ACCESS_DENIED      The CommunicateBuffer parameter or CommSize parameter,
+                                 if not omitted, are in address range that cannot be
+                                 accessed by the MM environment.
 
-  @retval EFI_SUCCESS                The message was successfully posted.
-  @retval EFI_INVALID_PARAMETER      The CommBuffer was NULL.
 **/
 EFI_STATUS
 EFIAPI
 SmmCommunicationCommunicate (
   IN CONST EFI_SMM_COMMUNICATION_PROTOCOL  *This,
   IN OUT VOID                              *CommBuffer,
-  IN OUT UINTN                             *CommSize
+  IN OUT UINTN                             *CommSize OPTIONAL
   );
 
 /**