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>
---
 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 735e099..c6f8191 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);
-- 
2.9.3.windows.2

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