[Patch 1/1] UefiCpuPkg: Always load microcode patch on AP processor.

["Siyuan, Fu" <siyuan.fu@intel.com>]

This patch updates the microcode loader to always perform a microcode detect
and load on both BSP and AP processor. This is to fix a potential microcode
revision mismatch issue in below situation:
1. Assume there are two microcode co-exists in flash: one production version
   and one debug version microcode.
2. FIT loads production microcode to BSP and all AP.
3. UefiCpuPkg loader loads debug microcode to BSP, and skip the loading on AP.
As a result, different microcode patches are loaded to BSP and AP, and trigger
microcode mismatch error during OS boot.

Bugzilla: https://bugzilla.tianocore.org/show_bug.cgi?id=2431

Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Signed-off-by: Siyuan Fu <siyuan.fu@intel.com>
---
 UefiCpuPkg/Library/MpInitLib/Microcode.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/UefiCpuPkg/Library/MpInitLib/Microcode.c b/UefiCpuPkg/Library/MpInitLib/Microcode.c
index 3da5bfb9cf2f..fa6f9681e55a 100644
--- a/UefiCpuPkg/Library/MpInitLib/Microcode.c
+++ b/UefiCpuPkg/Library/MpInitLib/Microcode.c
@@ -1,7 +1,7 @@
 /** @file
   Implementation of loading microcode on processors.
 
-  Copyright (c) 2015 - 2019, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2015 - 2020, Intel Corporation. All rights reserved.<BR>
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
 **/
@@ -105,12 +105,6 @@ MicrocodeDetect (
 
   CurrentRevision = GetCurrentMicrocodeSignature ();
   IsBspCallIn     = (ProcessorNumber == (UINTN)CpuMpData->BspNumber) ? TRUE : FALSE;
-  if (CurrentRevision != 0 && !IsBspCallIn) {
-    //
-    // Skip loading microcode if it has been loaded successfully
-    //
-    return;
-  }
 
   GetProcessorLocationByApicId (GetInitialApicId (), NULL, NULL, &ThreadId);
   if (ThreadId != 0) {
-- 
2.19.1.windows.1