KiGetThreadCpuSetMaskPointer

__int64 __fastcall KiGetThreadCpuSetMaskPointer(__int64 a1, _DWORD *a2){
  if( (*(_DWORD *)(a1 + 1296) & 0x20000) != 0 )
  {
    if( a2 )
      *a2 = (unsigned __int16)KiMaximumGroups;
    return *(_QWORD *)(a1 + 1536);
  }
  else
  {
    if( a2 )
      *a2 = 1;
    return a1 + 1536;
  }
}

Referenced by:

KeQueryCpuSetsThread
KeSetSelectedCpuSetsThread