The s390 iommu can only allow DMA transactions between the zPCI device entries start_dma and end_dma. Let's declare the regions before start_dma and after end_dma as reserved regions using the appropriate callback in iommu_ops. The reserved region may later be retrieved from sysfs or from the vfio iommu internal interface. This seems to me related with the work Shameer has started on vfio_iommu_type1 so I add Alex and Shameer to the CC list. Pierre Morel (1): iommu/s390: Declare s390 iommu reserved regions drivers/iommu/s390-iommu.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) -- 2.7.4