Updated: October 26, 2022

System memory management unit (IOMMU/SMMU) manager


smmuman options

Runs on:

QNX Neutrino


Options may be specified in the command line, or in a *.smmu configuration file, or both.

The smmuman service reads its startup configuration input in a single pass, from start to finish. If an option is specified more than once, the smmuman service does one of the following:

For more information, see Configuring smmuman,” Global options,” and the architecture-specific and board-specific entries in this chapter.


In all implementations, the smmuman service:


Until the smmuman service programs the IOMMU/SMMUs on a board with a DMA device's memory access permissions, that device has unrestricted access to memory.

Programming the IOMMU/SMMUs with DMA devices' memory access permissions specifies both the memory regions these devices may access and their permissions when accessing these regions (e.g., read only, read and write). It doesn't affect memory access managed by board MMUs (i.e., access that passes through the CPU).

When implemented in the host of a QNX Hypervisor system, in addition to the responsibilities listed above, the SMMUMAN: