This epic tracks exploring how to support cxl memory in nova.

CXL (compute express link) is an alternative host bus that can operate in several modes.
This epic specifically relates to CXL Memory mode which enabled cache coherent direct memory access to memory located on the CXL bus as if it was ram or persistent memory connect directly to the host memory controller.

in 2022 Samsung released CXL 2.0 type 3 memory expandtion modules into the market.

https://semiconductor.samsung.com/us/news-events/tech-blog/expanding-the-limits-of-memory-bandwidth-and-density-samsungs-cxl-dram-memory-expander/

these modules can be configured with daxctl to be used in system-ram mode

i.e. "daxctl reconfigure-device --no-movable --mode=system-ram dax0.0"

which will be presented to the host kernel as an additional numa node containing only memory.

nova does not support CXL devices in any mode today.
nova does not support creating vms with a numa topology where a numa cell only has CPU or memory.

as such since the cxl memory devices are model as separate numa nodes they are incompatible with nova numa support by design.

This epic tracks designing and developing a way to integrate CXL-memory into nova so that a future release of openstack can support this technology.