The file is used for 32 and 64 bit since:
commit cfb80c9eae
Author: Jeremy Fitzhardinge <jeremy@goop.org>
Date: Tue Dec 16 12:17:36 2008 -0800
x86: unify pci iommu setup and allow swiotlb to compile for 32 bit
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Ian Campbell