MdePkg/BaseCpuLibNull: Add Null version of CpuLib for host testing

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2798

The services in CpuLib usually generate exceptions in a unit test
host application.  Provide a Null instance that can be safely used.

This Null instance can also be used as a template for implementing
new instances of CpuLib.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Sean Brogan <sean.brogan@microsoft.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

MdePkg/Library/BaseCpuLibNull/BaseCpuLibNull.c

@@ -0,0 +1,37 @@
+/** @file
+  Null instance of CPU Library.
+
+  Copyright (c) 2020, Intel Corporation. All rights reserved.<BR>
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+/**
+  Places the CPU in a sleep state until an interrupt is received.
+
+  Places the CPU in a sleep state until an interrupt is received. If interrupts
+  are disabled prior to calling this function, then the CPU will be placed in a
+  sleep state indefinitely.
+
+**/
+VOID
+EFIAPI
+CpuSleep (
+  VOID
+  )
+{
+}
+
+/**
+  Flushes all the Translation Lookaside Buffers(TLB) entries in a CPU.
+
+  Flushes all the Translation Lookaside Buffers(TLB) entries in a CPU.
+
+**/
+VOID
+EFIAPI
+CpuFlushTlb (
+  VOID
+  )
+{
+}

MdePkg/Library/BaseCpuLibNull/BaseCpuLibNull.inf

@@ -0,0 +1,26 @@
+## @file
+#  Null instance of CPU Library.
+#
+#  Copyright (c) 2020, Intel Corporation. All rights reserved.<BR>
+#  SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+  INF_VERSION                    = 0x00010005
+  BASE_NAME                      = BaseCpuLibNull
+  MODULE_UNI_FILE                = BaseCpuLibNull.uni
+  FILE_GUID                      = 8A29AAA5-0FB7-44CC-8709-1344FE89B878
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = CpuLib
+
+#
+#  VALID_ARCHITECTURES           = IA32 X64 EBC ARM AARCH64 RISCV64
+#
+
+[Sources]
+  BaseCpuLibNull.c
+
+[Packages]
+  MdePkg/MdePkg.dec

MdePkg/Library/BaseCpuLibNull/BaseCpuLibNull.uni

@@ -0,0 +1,11 @@
+// /** @file
+// Null instance of CPU Library.
+//
+// Copyright (c) 2020, Intel Corporation. All rights reserved.<BR>
+// SPDX-License-Identifier: BSD-2-Clause-Patent
+//
+// **/
+
+#string STR_MODULE_ABSTRACT             #language en-US "Null Instance of CPU Library"
+
+#string STR_MODULE_DESCRIPTION          #language en-US "Null instance of CPU Library."

MdePkg/MdePkg.dsc

@@ -1,7 +1,7 @@
 ## @file
 # EFI/PI MdePkg Package
 #
-# Copyright (c) 2007 - 2018, Intel Corporation. All rights reserved.<BR>
+# Copyright (c) 2007 - 2020, Intel Corporation. All rights reserved.<BR>
 # Portions copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>
 # (C) Copyright 2020 Hewlett Packard Enterprise Development LP<BR>
 #
@@ -36,6 +36,7 @@
   MdePkg/Library/UefiFileHandleLib/UefiFileHandleLib.inf
   MdePkg/Library/BaseCacheMaintenanceLib/BaseCacheMaintenanceLib.inf
   MdePkg/Library/BaseCpuLib/BaseCpuLib.inf
+  MdePkg/Library/BaseCpuLibNull/BaseCpuLibNull.inf
   MdePkg/Library/BaseDebugLibNull/BaseDebugLibNull.inf
   MdePkg/Library/BaseDebugLibSerialPort/BaseDebugLibSerialPort.inf
   MdePkg/Library/BaseDebugPrintErrorLevelLib/BaseDebugPrintErrorLevelLib.inf