MdeModulePkg/VariableStandaloneMm: Notify variable write ready in MM

In Standalone MM, there is no notification to MM drivers that variable
write is ready. Install gSmmVariableWriteGuid into MM handle database
for the notification.

Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Ray Ni <ray.ni@intel.com>
Signed-off-by: Wei6 Xu <wei6.xu@intel.com>

MdeModulePkg/Universal/Variable/RuntimeDxe/VariableStandaloneMm.c

@@ -7,6 +7,8 @@ Copyright (c) 2018, Linaro, Ltd. All rights reserved. <BR>
 SPDX-License-Identifier: BSD-2-Clause-Patent
 
 **/
+
+#include <Library/MmServicesTableLib.h>
 #include <Library/StandaloneMmMemLib.h>
 #include "Variable.h"
 
@@ -67,6 +69,17 @@ VariableNotifySmmWriteReady (
   VOID
   )
 {
+  EFI_STATUS  Status;
+  EFI_HANDLE  Handle;
+
+  Handle = NULL;
+  Status = gMmst->MmInstallProtocolInterface (
+                    &Handle,
+                    &gSmmVariableWriteGuid,
+                    EFI_NATIVE_INTERFACE,
+                    NULL
+                    );
+  ASSERT_EFI_ERROR (Status);
 }
 
 /**

MdeModulePkg/Universal/Variable/RuntimeDxe/VariableStandaloneMm.inf

@@ -115,6 +115,7 @@
   gEfiMemoryOverwriteControlDataGuid            ## SOMETIMES_CONSUMES   ## Variable:L"MemoryOverwriteRequestControl"
   gEfiMemoryOverwriteRequestControlLockGuid     ## SOMETIMES_PRODUCES   ## Variable:L"MemoryOverwriteRequestControlLock"
 
+  gSmmVariableWriteGuid                         ## PRODUCES             ## GUID # Install protocol
   gEfiSystemNvDataFvGuid                        ## CONSUMES             ## GUID
   gEdkiiFaultTolerantWriteGuid                  ## SOMETIMES_CONSUMES   ## HOB