As an example, consider the AXI interfaces from the programmable logic to the PS that pass through the SMMU in the PS. When enabled, the SMMU also offers protection from DMA units in the PL restricted access to the PS memory region. This is protection in the context of a symmetric multiprocessing system running an OS. The OS on an APU can isolate the DMA from interfering with other devices under the APU. In a similar way, the SMMU can also be enabled to restrict DMA units or other hosts from accessing the PS memory region.