KeQueryGroupAffinity

KAFFINITY __stdcall KeQueryGroupAffinity(USHORT GroupNumber){
  if( GroupNumber >= KeActiveProcessors.Count )
    return 0i64;
  else
    return KeActiveProcessors.Bitmap[GroupNumber];
}

Referenced by:

EtwpProcessorRundown
ExpQuerySystemInformation
MmCreatePeb
NtCreateProfile
PopProcessorInformation
PpmEnableWmiInterface
PpmEventTraceProcessorPerformanceDomainRundown