Enable this option to debug the use of the DMA API by device drivers.
With this option you will be able to detect common bugs in device
drivers like double-freeing of DMA mappings or freeing mappings that
were never allocated.

This also attempts to catch cases where a page owned by DMA is
accessed by the cpu in a way that could cause data corruption. For
example, this enables cow_user_page() to check that the source page is
not undergoing DMA.

This option causes a performance degradation. Use only if you want to
debug device drivers and dma interactions.

If unsure, say N.

source code:

kernel/dma/debug.c