DMA

A defective device may be able to falsely initiate a DMA transfer over the bus. This type of data transfer may corrupt the system memory.

Some host bus bridges provide an IOMMU which allows you to map a DMA region (within the bus address space) to the system memory. On such hardware, the bus driver is able to protect the system memory (which is not used for DMA buffers) from corruption caused by a falsely initiated DMA transfer. The bus driver should not use a static one-to-one mapping (from the system memory to the bus space) to handle DMA transfers. Instead, it should manage IOMMU mappings dynamically. The dma_alloc() method maps a memory region to the bus space, enabling DMA transfers. The dma_free() method invalidates any mapping, disabling DMA to the memory region.

A defective device may still corrupt a DMA buffer managed by another device driver.