KeQueryGroupAffinity

NTSTATUS __fastcall KeQueryGroupAffinity(UINT16 a1){
  __int64 v1; 

  if( a1 >= KeActiveProcessors.Count )
    LODWORD(v1) = 0;
  else
    return KeActiveProcessors.Bitmap[a1];
  return v1;
}

Referenced by:

EtwpProcessorRundown
ExpQuerySystemInformation
MmCreatePeb
NtCreateProfile
PopProcessorInformation
PpmEnableWmiInterface
PpmEventTraceProcessorPerformanceDomainRundown