LinuxCon Europe + CloudOpen Europe

Linux kernel drivers map and unmap Dynamic Memory Access buffers using DMA API. DMA map operations can fail. Failure to check for errors can result in a variety of problems ranging from panics to silent data corruptions. Kernel panics can be fixed easily, however data corruptions are hard to debug. DMA mapping error analysis performed by the presenter found that more than 50% of map interface return values go unchecked in the kernel. Further more, several drivers fail to unmap buffers when an error occurs in the middle of a multi-page dma mapping attempt. Presenter added a new DMA Debug interface in Linux 3.9 to check for missing mapping error checks. This talk will share the results of the analysis and discuss how to find and fix missing mapping errors checks using the new interface. This talk will discuss possible enhancements to DMA Debug API to detect and flag unmap errors.