From c6b0feb39637867744bb7bffaa8534ecb1de707d Mon Sep 17 00:00:00 2001
From: Jeff Fan <jeff.fan@intel.com>
Date: Wed, 24 May 2017 13:53:30 +0800
Subject: [PATCH] UefiCpuPkg/MpInitLib: Check APIC mode change around AP
 function

If APIC ID values are changed during AP functions execution, we need to update
new APIC ID values in local data structure accordingly.

But if APIC mode change happened during AP function execution, we do not support
APIC ID value changed.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
---
 UefiCpuPkg/Library/MpInitLib/MpLib.c | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c
index 735e099b32..c6f81914d2 100644
--- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
+++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
@@ -547,6 +547,7 @@ ApWakeupFunction (
   volatile UINT32            *ApStartupSignalBuffer;
   CPU_INFO_IN_HOB            *CpuInfoInHob;
   UINT64                     ApTopOfStack;
+  UINTN                      CurrentApicMode;
 
   //
   // AP finished assembly code and begin to execute C code
@@ -560,6 +561,7 @@ ApWakeupFunction (
   ProgramVirtualWireMode ();
   SyncLocalApicTimerSetting (CpuMpData);
 
+  CurrentApicMode = GetApicMode ();
   while (TRUE) {
     if (CpuMpData->InitFlag == ApInitConfig) {
       //
@@ -627,11 +629,23 @@ ApWakeupFunction (
             ApStartupSignalBuffer = CpuMpData->CpuData[ProcessorNumber].StartupApSignal;
             CpuInfoInHob[ProcessorNumber].ApTopOfStack = CpuInfoInHob[CpuMpData->NewBspNumber].ApTopOfStack;
           } else {
-            //
-            // Re-get the CPU APICID and Initial APICID
-            //
-            CpuInfoInHob[ProcessorNumber].ApicId        = GetApicId ();
-            CpuInfoInHob[ProcessorNumber].InitialApicId = GetInitialApicId ();
+            if (CpuInfoInHob[ProcessorNumber].ApicId != GetApicId () ||
+                CpuInfoInHob[ProcessorNumber].InitialApicId != GetInitialApicId ()) {
+              if (CurrentApicMode != GetApicMode ()) {
+                //
+                // If APIC mode change happened during AP function execution,
+                // we do not support APIC ID value changed.
+                //
+                ASSERT (FALSE);
+                CpuDeadLoop ();
+              } else {
+                //
+                // Re-get the CPU APICID and Initial APICID if they are changed
+                //
+                CpuInfoInHob[ProcessorNumber].ApicId        = GetApicId ();
+                CpuInfoInHob[ProcessorNumber].InitialApicId = GetInitialApicId ();
+              }
+            }
           }
         }
         SetApState (&CpuMpData->CpuData[ProcessorNumber], CpuStateFinished);
-- 
2.39.2