KeSetSystemAffinityThreadEx

NTSTATUS __fastcall KeSetSystemAffinityThreadEx(UINT64 a1){
  unsigned __int16 v1; 
  _GROUP_AFFINITY Affinity; 
  _GROUP_AFFINITY PreviousAffinity; 

  v1 = 0;
  *(_QWORD *)&Affinity.Group = 0i64;
  Affinity.Mask = a1;
  PreviousAffinity = 0i64;
  if( KeForceGroupAwareness )
    v1 = KiActiveGroups - 1;
  Affinity.Group = v1;
  KeSetSystemGroupAffinityThread(&Affinity, &PreviousAffinity);
  return PreviousAffinity.Mask;
}

Referenced by:

KeSetSystemAffinityThread