[PATCH] MdeModulePkg PCD: Allow SkuId to be changed only once

[Star Zeng <star.zeng@intel.com>]

Current PI spec has no clear description about whether the
SkuId could be changed multiple times or not during one boot.

If the SkuId could be changed multiple times during one boot,
different modules may get inconsistent PCD values.
And DynamicHii PCD maps to UEFI variable, once one DynamicHii
PCD(UEFI variable) is set for one SkuId, then the PCD value
will be always from UEFI variable but not PCD database, even
the SkuId is set to other value.

This patch is to update PCD drivers to allow SkuId to be
changed only once during one boot.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
---
 MdeModulePkg/Universal/PCD/Dxe/Pcd.c | 27 +++++++++++++++++++++++----
 MdeModulePkg/Universal/PCD/Pei/Pcd.c | 28 ++++++++++++++++++++++++----
 2 files changed, 47 insertions(+), 8 deletions(-)

diff --git a/MdeModulePkg/Universal/PCD/Dxe/Pcd.c b/MdeModulePkg/Universal/PCD/Dxe/Pcd.c
index 1bb9098c04cf..9d710bbf1fb7 100644
--- a/MdeModulePkg/Universal/PCD/Dxe/Pcd.c
+++ b/MdeModulePkg/Universal/PCD/Dxe/Pcd.c
@@ -3,7 +3,7 @@
   produce the implementation of native PCD protocol and EFI_PCD_PROTOCOL defined in
   PI 1.4a Vol3.
 
-Copyright (c) 2006 - 2016, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2006 - 2017, Intel Corporation. All rights reserved.<BR>
 This program and the accompanying materials
 are licensed and made available under the terms and conditions of the BSD License
 which accompanies this distribution.  The full text of the license may be found at
@@ -272,19 +272,38 @@ DxePcdSetSku (
   SKU_ID    *SkuIdTable;
   UINTN     Index;
 
+  if (SkuId == mPcdDatabase.DxeDb->SystemSkuId) {
+    //
+    // The input SKU Id is equal to current SKU Id, return directly.
+    //
+    return;
+  }
+
+  if (mPcdDatabase.DxeDb->SystemSkuId != (SKU_ID) 0) {
+    DEBUG ((DEBUG_ERROR, "PcdDxe - The SKU Id could be changed only once."));
+    DEBUG ((
+      DEBUG_ERROR,
+      "PcdDxe - The SKU Id was set to 0x%lx already, it could not be set to 0x%lx any more.",
+      mPcdDatabase.DxeDb->SystemSkuId,
+      (SKU_ID) SkuId
+      ));
+    ASSERT (FALSE);
+    return;
+  }
+
   SkuIdTable = (SKU_ID *) ((UINT8 *) mPcdDatabase.DxeDb + mPcdDatabase.DxeDb->SkuIdTableOffset);
   for (Index = 0; Index < SkuIdTable[0]; Index++) {
     if (SkuId == SkuIdTable[Index + 1]) {
+      DEBUG ((EFI_D_INFO, "PcdDxe - Set current SKU Id to 0x%lx.\n", (SKU_ID) SkuId));
       mPcdDatabase.DxeDb->SystemSkuId = (SKU_ID) SkuId;
       return;
     }
   }
 
   //
-  // Invalid input SkuId, the default SKU Id will be used for the system.
+  // Invalid input SkuId, the default SKU Id will be still used for the system.
   //
-  DEBUG ((EFI_D_INFO, "PcdDxe - Invalid input SkuId, the default SKU Id will be used.\n"));
-  mPcdDatabase.DxeDb->SystemSkuId = (SKU_ID) 0;
+  DEBUG ((EFI_D_INFO, "PcdDxe - Invalid input SkuId, the default SKU Id will be still used.\n"));
   return;
 }
 
diff --git a/MdeModulePkg/Universal/PCD/Pei/Pcd.c b/MdeModulePkg/Universal/PCD/Pei/Pcd.c
index 668860b61c6c..a3f7337ceca3 100644
--- a/MdeModulePkg/Universal/PCD/Pei/Pcd.c
+++ b/MdeModulePkg/Universal/PCD/Pei/Pcd.c
@@ -1,7 +1,7 @@
 /** @file 
   All Pcd Ppi services are implemented here.
   
-Copyright (c) 2006 - 2016, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2006 - 2017, Intel Corporation. All rights reserved.<BR>
 (C) Copyright 2016 Hewlett Packard Enterprise Development LP<BR>
 This program and the accompanying materials
 are licensed and made available under the terms and conditions of the BSD License
@@ -262,19 +262,39 @@ PeiPcdSetSku (
   UINTN             Index;
 
   PeiPcdDb = GetPcdDatabase();
+
+  if (SkuId == PeiPcdDb->SystemSkuId) {
+    //
+    // The input SKU Id is equal to current SKU Id, return directly.
+    //
+    return;
+  }
+
+  if (PeiPcdDb->SystemSkuId != (SKU_ID) 0) {
+    DEBUG ((DEBUG_ERROR, "PcdPei - The SKU Id could be changed only once."));
+    DEBUG ((
+      DEBUG_ERROR,
+      "PcdPei - The SKU Id was set to 0x%lx already, it could not be set to 0x%lx any more.",
+      PeiPcdDb->SystemSkuId,
+      (SKU_ID) SkuId
+      ));
+    ASSERT (FALSE);
+    return;
+  }
+
   SkuIdTable = (SKU_ID *) ((UINT8 *) PeiPcdDb + PeiPcdDb->SkuIdTableOffset);
   for (Index = 0; Index < SkuIdTable[0]; Index++) {
     if (SkuId == SkuIdTable[Index + 1]) {
+      DEBUG ((EFI_D_INFO, "PcdPei - Set current SKU Id to 0x%lx.\n", (SKU_ID) SkuId));
       PeiPcdDb->SystemSkuId = (SKU_ID) SkuId;
       return;
     }
   }
 
   //
-  // Invalid input SkuId, the default SKU Id will be used for the system.
+  // Invalid input SkuId, the default SKU Id will be still used for the system.
   //
-  DEBUG ((EFI_D_INFO, "PcdPei - Invalid input SkuId, the default SKU Id will be used.\n"));
-  PeiPcdDb->SystemSkuId = (SKU_ID) 0;
+  DEBUG ((EFI_D_INFO, "PcdPei - Invalid input SkuId, the default SKU Id will be still used.\n"));
   return;
 }
 
-- 
2.7.0.windows.1