[$] Hotplugging and poisoning

Memory hotplugging is one of the least-loved areas of the memory-managementsubsystem; there are many use cases for it, but nobody has taken ownershipof it. A similar situation exists for hardware pagepoisoning, a somewhat neglected mechanism for dealing with memory errors.At the 2018 Linux Storage, Filesystem, and Memory-Management summit, MichalHocko and Mike Kravetz dedicated a pair of brief memory-management tracksessions to problems that have been encountered in these subsystems, one ofwhich seems more likely to get the attention it needs than the other.