On Sat, Oct 18, 2025 at 01:17:46PM -0400, Pasha Tatashin wrote: > This series addresses comments and combines into one the two > series [1] and [2], and adds review-bys. > > This series refactors the KHO framework to better support in-kernel > users like the upcoming LUO. The current design, which relies on a > notifier chain and debugfs for control, is too restrictive for direct > programmatic use. > > The core of this rework is the removal of the notifier chain in favor of > a direct registration API. This decouples clients from the shutdown-time > finalization sequence, allowing them to manage their preserved state > more flexibly and at any time. > > Also, this series fixes a memory corruption bug in KHO that occurs when > KFENCE is enabled. > > The root cause is that KHO metadata, allocated via kzalloc(), can be > randomly serviced by kfence_alloc(). When a kernel boots via KHO, the > early memblock allocator is restricted to a "scratch area". This forces > the KFENCE pool to be allocated within this scratch area, creating a > conflict. If KHO metadata is subsequently placed in this pool, it gets > corrupted during the next kexec operation. > > [1] > https://lore.kernel.org/all/[email protected] > [2] > https://lore.kernel.org/all/[email protected] > > Mike Rapoport (Microsoft) (1): > kho: drop notifiers > > Pasha Tatashin (9): > kho: allow to drive kho from within kernel > kho: make debugfs interface optional > kho: add interfaces to unpreserve folios and page ranes > kho: don't unpreserve memory during abort > liveupdate: kho: move to kernel/liveupdate > kho: move kho debugfs directory to liveupdate > liveupdate: kho: warn and fail on metadata or preserved memory in scratch > area > liveupdate: kho: Increase metadata bitmap size to PAGE_SIZE > liveupdate: kho: allocate metadata directly from the buddy allocator
The fixes should go before the preparation for LUO or even better as a separate series. I've reread the LUO preparation patches and I don't think they are useful on their own. They introduce a couple of unused interfaces and I think it's better to have them along with the rest of LUO patches. -- Sincerely yours, Mike.
