UefiCpuPkg/CpuMpPei: Place APs in proper loop mode after AP execution

After AP function is executed, we will place AP in proper loop mode. Because AP
maybe waken up by SMI or other reasons. We need to read signature in monitor
buffer to check if APs is waken up by BSP. If it is not waken up by BSP, we will
continue to place them into proper loop mode.

Contributed-under: TianoCore Contribution Agreement 1.0
Cc: Feng Tian <feng.tian@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Tested-by: Michael Kinney <michael.d.kinney@intel.com>
Reviewed-by: Michael Kinney <michael.d.kinney@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19345 6f19259b-4bc3-4df7-8a09-765794883524

UefiCpuPkg/CpuMpPei/CpuMpPei.h

@@ -38,6 +38,7 @@
 #include <Library/SynchronizationLib.h>
 #include <Library/TimerLib.h>
 #include <Library/UefiCpuLib.h>
+#include <Library/CpuLib.h>
 
 #include "Microcode.h"
 
@@ -50,6 +51,8 @@ typedef enum {
   CpuStateDisabled
 } CPU_STATE;
 
+#define WAKEUP_AP_SIGNAL SIGNATURE_32 ('S', 'T', 'A', 'P')
+
 typedef enum {
   ApInHltLoop   = 1,
   ApInMwaitLoop = 2,