1 files changed, 50 insertions, 1 deletions
diff --git a/UefiCpuPkg/CpuDxe/CpuMp.c b/UefiCpuPkg/CpuDxe/CpuMp.c
index de599dad6a..88bf95269d 100644
--- a/UefiCpuPkg/CpuDxe/CpuMp.c
+++ b/UefiCpuPkg/CpuDxe/CpuMp.c
@@ -31,10 +31,59 @@ EFI_MP_SERVICES_PROTOCOL  mMpServicesTemplate = {
   NULL, // StartupThisAP,
   NULL, // SwitchBSP,
   NULL, // EnableDisableAP,
-  NULL  // WhoAmI
+  WhoAmI
 };
 
 /**
+  This return the handle number for the calling processor.  This service may be
+  called from the BSP and APs.
+
+  This service returns the processor handle number for the calling processor.
+  The returned value is in the range from 0 to the total number of logical
+  processors minus 1. The total number of logical processors can be retrieved
+  with EFI_MP_SERVICES_PROTOCOL.GetNumberOfProcessors(). This service may be
+  called from the BSP and APs. If ProcessorNumber is NULL, then EFI_INVALID_PARAMETER
+  is returned. Otherwise, the current processors handle number is returned in
+  ProcessorNumber, and EFI_SUCCESS is returned.
+
+  @param[in]  This             A pointer to the EFI_MP_SERVICES_PROTOCOL instance.
+  @param[out] ProcessorNumber  The handle number of AP that is to become the new
+                               BSP. The range is from 0 to the total number of
+                               logical processors minus 1. The total number of
+                               logical processors can be retrieved by
+                               EFI_MP_SERVICES_PROTOCOL.GetNumberOfProcessors().
+
+  @retval EFI_SUCCESS             The current processor handle number was returned
+                                  in ProcessorNumber.
+  @retval EFI_INVALID_PARAMETER   ProcessorNumber is NULL.
+
+**/
+EFI_STATUS
+EFIAPI
+WhoAmI (
+  IN EFI_MP_SERVICES_PROTOCOL  *This,
+  OUT UINTN                    *ProcessorNumber
+  )
+{
+  UINTN   Index;
+  UINT32  ProcessorId;
+
+  if (ProcessorNumber == NULL) {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  ProcessorId = GetApicId ();
+  for (Index = 0; Index < mMpSystemData.NumberOfProcessors; Index++) {
+    if (mMpSystemData.CpuDatas[Index].Info.ProcessorId == ProcessorId) {
+      break;
+    }
+  }
+
+  *ProcessorNumber = Index;
+  return EFI_SUCCESS;
+}
+
+/**
   Application Processors do loop routine
   after switch to its own stack.