Validating direct memory access interfaces with conformance checking

Direct Memory Access (DMA) interfaces are a common and important component of Hardware/Software (HW/SW) interfaces between peripheral devices and their device drivers. We present a HW/SW co-validation framework to validate DMA interface implementations of a device and its driver. This framework employs a virtual prototype of the device as a reference model and performs co-validation in two stages: (1) conformance checking which checks the DMA interface conformance between the device and its virtual prototype; (2) property checking which checks device/driver interactions across the DMA interface. In conformance checking, the virtual prototype infers the device state transitions by taking the same driver request sequence to the device. Property checking verifies system properties over the device state transitions exposed through the virtual prototype. This framework assists HW/SW integration validation by detecting DMA interface bugs in both devices and drivers. Furthermore, we have developed three key techniques: capture-on-write policy, partial capture, and environmental input prediction, to address two major challenges in scaling the framework: DMA capture overhead and imprecise environmental input simulation. We have applied this approach to four Ethernet adapters, discovering 12 serious DMA interface bugs from the devices, their virtual prototypes and their drivers. The results demonstrate that our approach has major potential in facilitating HW/SW co-validation.