diff --git a/ArmVirtPkg/Library/DebugLibFdtPL011Uart/User.c b/ArmVirtPkg/Library/DebugLibFdtPL011Uart/User.c
index 6e012ee85b..2229cffde0 100644
--- a/ArmVirtPkg/Library/DebugLibFdtPL011Uart/User.c
+++ b/ArmVirtPkg/Library/DebugLibFdtPL011Uart/User.c
@@ -29,10 +29,11 @@ DebugLibFdtPL011UartUserConstructor (
   for (Index = 0; Index < SystemTable->NumberOfTableEntries; ++Index) {
     if (CompareGuid (&gEarlyPL011BaseAddressGuid, &(SystemTable->ConfigurationTable[Index].VendorGuid))) {
       mDebugLibFdtPL011UartAddress = (UINTN)SystemTable->ConfigurationTable[Index].VendorTable;
+      return EFI_SUCCESS;
     }
   }
 
-  return EFI_SUCCESS;
+  return EFI_NOT_FOUND;
 }
 
 /**
diff --git a/MdeModulePkg/Core/Dxe/SysCall/Initialization.c b/MdeModulePkg/Core/Dxe/SysCall/Initialization.c
index ee9a256080..b3a731ce63 100644
--- a/MdeModulePkg/Core/Dxe/SysCall/Initialization.c
+++ b/MdeModulePkg/Core/Dxe/SysCall/Initialization.c
@@ -73,6 +73,15 @@ InitializeRing3 (
     EFI_MEMORY_XP | EFI_MEMORY_USER
     );
 
+  Status = InitializePlatform (&gRing3Data->SystemTable);
+  if (EFI_ERROR (Status)) {
+    CoreFreePages (
+      (EFI_PHYSICAL_ADDRESS)(UINTN)gRing3Data,
+      EFI_SIZE_TO_PAGES (sizeof (RING3_DATA))
+      );
+    return Status;
+  }
+
   //
   // Initialize DxeRing3 with Supervisor privileges.
   //
@@ -81,14 +90,16 @@ InitializeRing3 (
 
   SetUefiImageProtectionAttributes (mDxeRing3, FALSE);
 
+  AllowSupervisorAccessToUserMemory ();
   Status = Image->EntryPoint (ImageHandle, (EFI_SYSTEM_TABLE *)gRing3Data);
 
-  SetUefiImageProtectionAttributes (mDxeRing3, TRUE);
-
   gRing3EntryPoint = gRing3Data->EntryPoint;
 
   gRing3Data->SystemTable.BootServices    = gRing3Data->BootServices;
   gRing3Data->SystemTable.RuntimeServices = gRing3Data->RuntimeServices;
+  ForbidSupervisorAccessToUserMemory ();
+
+  SetUefiImageProtectionAttributes (mDxeRing3, TRUE);
 
   Status = CoreAllocatePages (
              AllocateAnyPages,
@@ -112,19 +123,6 @@ InitializeRing3 (
     EFI_MEMORY_XP | EFI_MEMORY_USER
     );
 
-  Status = InitializePlatform (&gRing3Data->SystemTable);
-  if (EFI_ERROR (Status)) {
-    CoreFreePages (
-      (EFI_PHYSICAL_ADDRESS)(UINTN)gRing3Data,
-      EFI_SIZE_TO_PAGES (sizeof (RING3_DATA))
-      );
-    CoreFreePages (
-      (EFI_PHYSICAL_ADDRESS)(UINTN)gRing3Interfaces,
-      RING3_INTERFACES_PAGES
-      );
-    return Status;
-  }
-
   mExceptionAddresses = GetExceptionAddresses ();
 
   PeiHob.Raw = GetHobList ();