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Explore the implementation of CXL HDM-DB (Host-managed Device Memory – Device-coherent with Back-invalidate) support in Linux through this 29-minute conference talk from the Linux Plumbers Conference. Learn about this new type of device memory introduced in CXL 3.0 that enables Type 2 and Type 3 devices to manage memory coherence directly, with the device acting as the final arbiter of coherence for addresses it owns. Discover how HDM-DB allows devices to implement inclusive snoop filters to track host caching of device memory, reducing snooping overhead and enabling low-latency direct peer-to-peer communication without constant host CPU involvement. Examine the current upstream support and discuss future development directions, including general back-invalidate discoverability approaches, integration with Type 2 and HDM-D model support work, region creation semantics for both Type 2 and Type 3 devices, and practical use cases within Linux environments.
