On 4/13/26 16:49, David Hildenbrand (Arm) wrote: > On 3/21/26 16:03, Gregory Price wrote: >> The dax kmem driver currently onlines memory during probe using the >> system default policy, with no way to control or query the region state >> at runtime - other than by inspecting the state of individual blocks. >> >> Offlining and removing an entire region requires operating on individual >> memory blocks, creating race conditions where external entities can >> interfere between the offline and remove steps. >> >> The problem was discussed specifically in the LPC2025 device memory >> sessions - https://lpc.events/event/19/contributions/2016/ - where >> it was discussed how the non-atomic interface for dax hotplug is causing >> issues in some distributions which have competing userland controllers >> that interfere with each other. >> >> This series adds a sysfs "hotplug" attribute for atomic whole-device >> hotplug control, along with the mm and dax plumbing to support it. >> >> The first five patches prepare the mm and dax layers: >> >> 1. Consolidate memory-tier type deduplication into mt_get_memory_type(), >> removing redundant per-driver infrastructure. >> 2. Add a memory_block_align_range() helper for hotplug range alignment. >> 3-5. Thread an explicit online_type through the memory hotplug and dax >> paths, allowing drivers to specify a preferred auto-online policy >> (ZONE_NORMAL vs ZONE_MOVABLE) instead of being forced to the >> system default. >> >> The last three patches build the dax/kmem feature: >> >> 6. Plumb online_type through the dax device creation path. >> 7. Extract hotplug/hotremove into helper functions to separate resource >> lifecycle from memory onlining. >> 8. Add the "hotplug" sysfs attribute supporting three states: >> - "unplug": memory blocks removed >> - "online": online as normal system RAM >> - "online_movable": online in ZONE_MOVABLE >> >> Transitions are atomic across all ranges in the device. Backward >> compatibility is preserved: probe still auto-onlines when the configured >> policy matches the system default. >> >> Specific notes for maintainers: >> >> I downgraded a BUG() to a WARN() when unbind is called while the dax >> device is not un an UNPLUGGED state. This is because the old pattern of >> toggling individual memory blocks is still used by userland tools, and >> will disconnect the `hotplug` value from the actual state of the overall >> memory region. >> >> Unless we move to deprecate per-block controls, we should just WARN() >> instead of BUG() as an indicator that userland tools need to be updated >> to use the new pattern (the old pattern is subject to race conditions). >> >> The first two commits are semi-unrelated cleanups that conflict with the >> changes made in the refactoring commits. (memory-tier dedup and align_range >> helper). These are intended to be used for future cxl region extensions, >> but if you prefer them to be dropped or submitted separately let me >> know. >> >> This is technically v3, but the patch line has diverged considerably and >> I've reworked the cover letter, apologies for prior obtuseness >> Link: https://lore.kernel.org/all/[email protected]/ > > > Hi Gregory, > > against which branch / base commit is this series? >
b4 am --guess-base Was helpful :) -- Cheers, David
