When ACPI && NUMA, pxm_to_node is used and it exists in drivers/acpi/numa.c

Tony said:

  The patch makes sense ...  if you pick both of "ACPI" and "NUMA", then you
  need (and should automatically be given) ACPI_NUMA too.

  The only open question is whether there is a better way of getting there.
  Perhaps with less configuration options in the first place?  We are heading
  towards a future where so many systems will be NUMA that there would seem to
  be little benefit in keeping ACPI_NUMA separate from ACPI ...  but perhaps
  we aren't quite there yet.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujtisu.com>
Cc: Len Brown <lenb@kernel.org>
Acked-by: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>