StandaloneMmPkg/Core: Introduce MM Communication Buffer

Get the MM Communication context from the MM Communication Buffer,
instead of the pointer inside gMmCorePrivate.
In the MmEntryPoint, check IsCommBufferValid from MM_COMM_BUFFER to
decide whether the MMI is Synchronous MMI or Asynchronous MMI. If it
is a Synchronous MMI, MM Core shadows the communication buffer into
a internal copy, then invokes the MMI handlers, lastly copies data
back to the MM Communication Buffer and set the return status.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Jiaxin Wu <jiaxin.wu@intel.com>
Signed-off-by: Wei6 Xu <wei6.xu@intel.com>

StandaloneMmPkg/Core/StandaloneMmCore.c

@@ -88,6 +88,8 @@ MM_CORE_MMI_HANDLERS  mMmCoreMmiHandlers[] = {
 
 UINTN                 mMmramRangeCount;
 EFI_MMRAM_DESCRIPTOR  *mMmramRanges;
+MM_COMM_BUFFER        *mMmCommunicationBuffer;
+VOID                  *mInternalCommBufferCopy;
 
 /**
   Place holder function until all the MM System Table Service are available.
@@ -397,6 +399,62 @@ MmCoreInstallLoadedImage (
   ASSERT_EFI_ERROR (Status);
 }
 
+/**
+  Prepare communication buffer for MMI.
+**/
+VOID
+MmCorePrepareCommunicationBuffer (
+  VOID
+  )
+{
+  EFI_STATUS            Status;
+  EFI_HOB_GUID_TYPE     *GuidHob;
+  EFI_PHYSICAL_ADDRESS  Buffer;
+
+  mMmCommunicationBuffer  = NULL;
+  mInternalCommBufferCopy = NULL;
+
+  GuidHob = GetFirstGuidHob (&gMmCommBufferHobGuid);
+  ASSERT (GuidHob != NULL);
+  if (GuidHob == NULL) {
+    return;
+  }
+
+  mMmCommunicationBuffer = (MM_COMM_BUFFER *)GET_GUID_HOB_DATA (GuidHob);
+  DEBUG ((
+    DEBUG_INFO,
+    "MM Communication Buffer is at %x, number of pages is %x\n",
+    mMmCommunicationBuffer->PhysicalStart,
+    mMmCommunicationBuffer->NumberOfPages
+    ));
+  ASSERT (mMmCommunicationBuffer->PhysicalStart != 0 && mMmCommunicationBuffer->NumberOfPages != 0);
+
+  if (!MmIsBufferOutsideMmValid (
+         mMmCommunicationBuffer->PhysicalStart,
+         EFI_PAGES_TO_SIZE (mMmCommunicationBuffer->NumberOfPages)
+         ))
+  {
+    mMmCommunicationBuffer = NULL;
+    DEBUG ((DEBUG_ERROR, "MM Communication Buffer is invalid!\n"));
+    ASSERT (FALSE);
+    return;
+  }
+
+  Status = MmAllocatePages (
+             AllocateAnyPages,
+             EfiRuntimeServicesData,
+             mMmCommunicationBuffer->NumberOfPages,
+             &Buffer
+             );
+  ASSERT_EFI_ERROR (Status);
+  if (EFI_ERROR (Status)) {
+    return;
+  }
+
+  mInternalCommBufferCopy = (VOID *)(UINTN)Buffer;
+  DEBUG ((DEBUG_INFO, "Internal Communication Buffer Copy is at %p\n", mInternalCommBufferCopy));
+}
+
 /**
   The main entry point to MM Foundation.
 
@@ -414,6 +472,8 @@ MmEntryPoint (
 {
   EFI_STATUS                 Status;
   EFI_MM_COMMUNICATE_HEADER  *CommunicateHeader;
+  MM_COMM_BUFFER_STATUS      *CommunicationStatus;
+  UINTN                      BufferSize;
 
   DEBUG ((DEBUG_INFO, "MmEntryPoint ...\n"));
 
@@ -440,33 +500,65 @@ MmEntryPoint (
   // Check to see if this is a Synchronous MMI sent through the MM Communication
   // Protocol or an Asynchronous MMI
   //
-  if (gMmCorePrivate->CommunicationBuffer != 0) {
+  if ((mMmCommunicationBuffer != NULL) && (mInternalCommBufferCopy != NULL)) {
-    //
+    CommunicationStatus = (MM_COMM_BUFFER_STATUS *)(UINTN)mMmCommunicationBuffer->Status;
-    // Synchronous MMI for MM Core or request from Communicate protocol
+    if (CommunicationStatus->IsCommBufferValid) {
-    //
-    if (!MmIsBufferOutsideMmValid ((UINTN)gMmCorePrivate->CommunicationBuffer, gMmCorePrivate->BufferSize)) {
       //
-      // If CommunicationBuffer is not in valid address scope, return EFI_INVALID_PARAMETER
+      // Synchronous MMI for MM Core or request from Communicate protocol
       //
-      gMmCorePrivate->CommunicationBuffer = 0;
+      CommunicateHeader = (EFI_MM_COMMUNICATE_HEADER *)(UINTN)mMmCommunicationBuffer->PhysicalStart;
-      gMmCorePrivate->ReturnStatus        = EFI_INVALID_PARAMETER;
+      BufferSize        = OFFSET_OF (EFI_MM_COMMUNICATE_HEADER, Data) + CommunicateHeader->MessageLength;
-    } else {
+      if (BufferSize <= EFI_PAGES_TO_SIZE (mMmCommunicationBuffer->NumberOfPages)) {
-      CommunicateHeader           = (EFI_MM_COMMUNICATE_HEADER *)(UINTN)gMmCorePrivate->CommunicationBuffer;
+        //
-      gMmCorePrivate->BufferSize -= OFFSET_OF (EFI_MM_COMMUNICATE_HEADER, Data);
+        // Shadow the data from MM Communication Buffer to internal buffer
-      Status                      = MmiManage (
+        //
-                                      &CommunicateHeader->HeaderGuid,
+        CopyMem (
-                                      NULL,
+          mInternalCommBufferCopy,
-                                      CommunicateHeader->Data,
+          (VOID *)(UINTN)mMmCommunicationBuffer->PhysicalStart,
-                                      (UINTN *)&gMmCorePrivate->BufferSize
+          BufferSize
-                                      );
+          );
-      //
+        ZeroMem (
-      // Update CommunicationBuffer, BufferSize and ReturnStatus
+          (UINT8 *)mInternalCommBufferCopy + BufferSize,
-      // Communicate service finished, reset the pointer to CommBuffer to NULL
+          EFI_PAGES_TO_SIZE (mMmCommunicationBuffer->NumberOfPages) - BufferSize
-      //
+          );
-      gMmCorePrivate->BufferSize         += OFFSET_OF (EFI_MM_COMMUNICATE_HEADER, Data);
+
-      gMmCorePrivate->CommunicationBuffer = 0;
+        CommunicateHeader = (EFI_MM_COMMUNICATE_HEADER *)mInternalCommBufferCopy;
-      gMmCorePrivate->ReturnStatus        = (Status == EFI_SUCCESS) ? EFI_SUCCESS : EFI_NOT_FOUND;
+        BufferSize        = CommunicateHeader->MessageLength;
+        Status            = MmiManage (
+                              &CommunicateHeader->HeaderGuid,
+                              NULL,
+                              CommunicateHeader->Data,
+                              &BufferSize
+                              );
+
+        BufferSize = BufferSize + OFFSET_OF (EFI_MM_COMMUNICATE_HEADER, Data);
+        if (BufferSize <= EFI_PAGES_TO_SIZE (mMmCommunicationBuffer->NumberOfPages)) {
+          //
+          // Copy the data back to MM Communication Buffer
+          //
+          CopyMem (
+            (VOID *)(UINTN)mMmCommunicationBuffer->PhysicalStart,
+            mInternalCommBufferCopy,
+            BufferSize
+            );
+        } else {
+          DEBUG ((DEBUG_ERROR, "Returned buffer size is larger than the size of MM Communication Buffer\n"));
+          ASSERT (FALSE);
+        }
+
+        //
+        // Update CommunicationBuffer, BufferSize and ReturnStatus
+        // Communicate service finished, reset the pointer to CommBuffer to NULL
+        //
+        CommunicationStatus->ReturnBufferSize = BufferSize;
+        CommunicationStatus->ReturnStatus     = (Status == EFI_SUCCESS) ? EFI_SUCCESS : EFI_NOT_FOUND;
+      } else {
+        DEBUG ((DEBUG_ERROR, "Input buffer size is larger than the size of MM Communication Buffer\n"));
+        ASSERT (FALSE);
+      }
     }
+  } else {
+    DEBUG ((DEBUG_ERROR, "No valid communication buffer, no Synchronous MMI will be processed\n"));
   }
 
   //
@@ -738,6 +830,8 @@ StandaloneMmMain (
     DEBUG ((DEBUG_INFO, "MmiHandlerRegister - GUID %g - Status %d\n", mMmCoreMmiHandlers[Index].HandlerType, Status));
   }
 
+  MmCorePrepareCommunicationBuffer ();
+
   //
   // Install Loaded Image Protocol form MM Core
   //

StandaloneMmPkg/Core/StandaloneMmCore.h

@@ -30,6 +30,7 @@
 #include <Guid/HobList.h>
 #include <Guid/MmFvDispatch.h>
 #include <Guid/MmramMemoryReserve.h>
+#include <Guid/MmCommBuffer.h>
 
 #include <Library/StandaloneMmCoreEntryPoint.h>
 #include <Library/BaseLib.h>

StandaloneMmPkg/Core/StandaloneMmCore.inf

@@ -76,6 +76,7 @@
   gEfiEventLegacyBootGuid
   gEfiEventExitBootServicesGuid
   gEfiEventReadyToBootGuid
+  gMmCommBufferHobGuid
 
 [Pcd]
   gStandaloneMmPkgTokenSpaceGuid.PcdFwVolMmMaxEncapsulationDepth    ##CONSUMES