On Wed, Aug 12, 2026 at 02:01:12PM +0200, Pankaj Gupta wrote: > > > > Bonus Configuration: HBM device memory tiering > > ============================================== > > echo 1 > dax0.0/private # make the node private > > echo 0 > dax0.0/adistance # highest tier > > echo 1 > dax0.0/reclaim # reclaim active > > echo 1 > dax0.0/demotion # may demote from the node > > echo 1 > dax0.0/user_numa # mbind() > > echo online_movable > dax0.0/state > > echo 1 > numa/demotion_enabled > > I am bit confused by the HBM device example being discovered as a DAX > device. Is it to > only to showcase the use-case? Or we see HBM device is actually > expected to be discovered as > DAX device with N_MEMORY_PRIVATE? >
"actually expected to be" -> no. there's no requirement HBM be discovered and boudn to DAX, DAX is simply a convenient intermediary to memory-hotplug. This is at best a demonstration. A device driver could very well just call memory-hotplug directly, or its memory could be brought up as a private node via a boot paremeter (which I have sculpted for v7). The former is preferred, but there's a bit of a chicken/egg scenario for bootstrapping. Most of these UAPI extensions are going to be consolidated into a debugfs interface for testing purposes only in v7. I've been working on aggressive Linux Test Project test expansion to ensure there is no UAPI regressions. ~Gregory
