HPE Adapt (2 of at least 4) - Handle pages being unmapped.

[andyw-lala]

HPE is planning to work with the community to enhance this xpmem repo, to provide the functionality currently supported by our in-house COS-only version. This issue is number 2 in a series of at least 4, and seeks to identify the known issues that must be addressed.

HPE COS xpmem relies on kernel patches to handle the scenario where pages are unmapped out from under xpmem (I believe this is know to occur with profilers/debuggers.) I am told that the linux kernel deprecated the notification mechanism previously used.

Need to investigate whether this xpmem is susceptible to the issue, or if it has already been addressed.