[Patch] UefiCpuPkg/MpInitLib: Optimize get processor number performance.

[Eric Dong <eric.dong@intel.com>]

Current function has low performance because it calls GetApicId
many times.

New logic first try to base on the stack range used by AP to
find the processor number. If this solution failed, then call
GetApicId once and base on this value to search the processor.

Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Jeff Fan <vanjeff_919@hotmail.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Eric Dong <eric.dong@intel.com>
---
 UefiCpuPkg/Library/MpInitLib/MpLib.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c
index eb2765910c..abd65bee1a 100644
--- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
+++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
@@ -418,7 +418,8 @@ ApInitializeSync (
 }
 
 /**
-  Find the current Processor number by APIC ID.
+  First try to find the current Processor number by stack address,
+  if it failed, then base on APIC ID.
 
   @param[in]  CpuMpData         Pointer to PEI CPU MP Data
   @param[out] ProcessorNumber   Return the pocessor number found
@@ -435,16 +436,34 @@ GetProcessorNumber (
   UINTN                   TotalProcessorNumber;
   UINTN                   Index;
   CPU_INFO_IN_HOB         *CpuInfoInHob;
+  UINT32                  CurrentApicId;
 
+  TotalProcessorNumber = CpuMpData->CpuCount;
   CpuInfoInHob = (CPU_INFO_IN_HOB *) (UINTN) CpuMpData->CpuInfoInHob;
 
-  TotalProcessorNumber = CpuMpData->CpuCount;
+  //
+  // First try to base on current stack address to find the AP index.
+  // &TotalProcessorNumber value located in the stack range.
+  //
   for (Index = 0; Index < TotalProcessorNumber; Index ++) {
-    if (CpuInfoInHob[Index].ApicId == GetApicId ()) {
+    if ((CpuInfoInHob[Index].ApTopOfStack > (UINTN) (&TotalProcessorNumber)) &&
+        (CpuInfoInHob[Index].ApTopOfStack - CpuMpData->CpuApStackSize < (UINTN) (&TotalProcessorNumber))) {
       *ProcessorNumber = Index;
       return EFI_SUCCESS;
     }
   }
+
+  //
+  // If can't base on stack to find the AP index, use the APIC ID.
+  //
+  CurrentApicId = GetApicId ();
+  for (Index = 0; Index < TotalProcessorNumber; Index ++) {
+    if (CpuInfoInHob[Index].ApicId == CurrentApicId) {
+      *ProcessorNumber = Index;
+      return EFI_SUCCESS;
+    }
+  }
+
   return EFI_NOT_FOUND;
 }
 
-- 
2.15.0.windows.1