OvmfPkg: QemuFlashFvbServicesRuntimeDxe: Abstract out SMM/DXE functions

This update refactors QemuFlashFvbServicesRuntimeDxe to abstract out
direct calls to SMM and DXE specific functions.

Specifically, dynamic PCD usage and gBS references have been moved to SMM
specific files.

The constructor functionality has been relocated to a common
implementation and is invoked from their respective entry points.

These changes lay the groundwork for supporting a Standalone MM-based
solution in the future.

Signed-off-by: Kun Qin <kun.qin@microsoft.com>

OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FwBlockService.c

@@ -27,9 +27,7 @@
 #include <Library/BaseMemoryLib.h>
 #include <Library/DebugLib.h>
 #include <Library/DevicePathLib.h>
-#include <Library/DxeServicesTableLib.h>
 #include <Library/MemoryAllocationLib.h>
-#include <Library/UefiBootServicesTableLib.h>
 
 #include "FwBlockService.h"
 #include "QemuFlash.h"
@@ -976,7 +974,6 @@ FvbInitialize (
   EFI_PHYSICAL_ADDRESS        BaseAddress;
   UINTN                       Length;
   UINTN                       NumOfBlocks;
-  RETURN_STATUS               PcdStatus;
 
   if (EFI_ERROR (QemuFlashInitialize ())) {
     //
@@ -1129,7 +1126,8 @@ FvbInitialize (
   //
   InstallVirtualAddressChangeHandler ();
 
-  PcdStatus = PcdSetBoolS (PcdOvmfFlashVariablesEnable, TRUE);
-  ASSERT_RETURN_ERROR (PcdStatus);
+  // Abstract dynamic PCD set to support Standalone MM
+  UpdateQemuFlashVariablesEnable ();
+
   return EFI_SUCCESS;
 }

OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FwBlockService.h

@@ -194,4 +194,9 @@ SetPcdFlashNvStorageBaseAddresses (
   VOID
   );
 
+VOID
+UpdateQemuFlashVariablesEnable (
+  VOID
+  );
+
 #endif

OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FwBlockServiceDxe.c

@@ -244,3 +244,14 @@ SetPcdFlashNvStorageBaseAddresses (
                 );
   ASSERT_RETURN_ERROR (PcdStatus);
 }
+
+VOID
+UpdateQemuFlashVariablesEnable (
+  VOID
+  )
+{
+  RETURN_STATUS  PcdStatus;
+
+  PcdStatus = PcdSetBoolS (PcdOvmfFlashVariablesEnable, TRUE);
+  ASSERT_RETURN_ERROR (PcdStatus);
+}

OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FwBlockServiceSmm.c

@@ -84,3 +84,14 @@ SetPcdFlashNvStorageBaseAddresses (
   // Do nothing.
   //
 }
+
+VOID
+UpdateQemuFlashVariablesEnable (
+  VOID
+  )
+{
+  RETURN_STATUS  PcdStatus;
+
+  PcdStatus = PcdSetBoolS (PcdOvmfFlashVariablesEnable, TRUE);
+  ASSERT_RETURN_ERROR (PcdStatus);
+}