linux-kernel - [PATCH v8 0/8] liveupdate: Rework KHO for in-kernel users

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Message-ID: <20251024161002.747372-1-pasha.tatashin@soleen.com>
Date: Fri, 24 Oct 2025 12:09:54 -0400
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: akpm@...ux-foundation.org,
	brauner@...nel.org,
	corbet@....net,
	graf@...zon.com,
	jgg@...pe.ca,
	linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	linux-mm@...ck.org,
	masahiroy@...nel.org,
	ojeda@...nel.org,
	pasha.tatashin@...een.com,
	pratyush@...nel.org,
	rdunlap@...radead.org,
	rppt@...nel.org,
	tj@...nel.org
Subject: [PATCH v8 0/8] liveupdate: Rework KHO for in-kernel users

Changelog:
v8:
Added review-bys and addressed comments from Mike Rapoport and
Pratyush Yadav.
Added "memblock: Unpreserve memory in case of error" to handle
rollback if preserve fails half way through.

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.

In support of this new model, this series also:
 - Exports kho_finalize() and kho_abort() for programmatic control.
 - Makes the debugfs interface optional.
 - Introduces APIs to unpreserve memory and fixes a bug in the abort
   path where client state was being incorrectly discarded. Note that
   this is an interim step, as a more comprehensive fix is planned as
   part of the stateless KHO work [1].
 - Moves all KHO code into a new kernel/liveupdate/ directory to
   consolidate live update components.

[1] https://lore.kernel.org/all/20251020100306.2709352-1-jasonmiu@google.com

Mike Rapoport (Microsoft) (1):
  kho: drop notifiers

Pasha Tatashin (7):
  kho: allow to drive kho from within kernel
  kho: make debugfs interface optional
  kho: add interfaces to unpreserve folios and page ranges
  kho: don't unpreserve memory during abort
  liveupdate: kho: move to kernel/liveupdate
  liveupdate: kho: move kho debugfs directory to liveupdate
  memblock: Unpreserve memory in case of error

 Documentation/core-api/kho/concepts.rst       |   2 +-
 MAINTAINERS                                   |   3 +-
 include/linux/kexec_handover.h                |  53 +-
 init/Kconfig                                  |   2 +
 kernel/Kconfig.kexec                          |  24 -
 kernel/Makefile                               |   3 +-
 kernel/kexec_handover_internal.h              |  16 -
 kernel/liveupdate/Kconfig                     |  39 ++
 kernel/liveupdate/Makefile                    |   5 +
 kernel/{ => liveupdate}/kexec_handover.c      | 508 +++++++-----------
 .../{ => liveupdate}/kexec_handover_debug.c   |   0
 kernel/liveupdate/kexec_handover_debugfs.c    | 219 ++++++++
 kernel/liveupdate/kexec_handover_internal.h   |  56 ++
 lib/test_kho.c                                |  33 +-
 mm/memblock.c                                 |  82 ++-
 tools/testing/selftests/kho/init.c            |   2 +-
 tools/testing/selftests/kho/vmtest.sh         |   1 +
 17 files changed, 590 insertions(+), 458 deletions(-)
 delete mode 100644 kernel/kexec_handover_internal.h
 create mode 100644 kernel/liveupdate/Kconfig
 create mode 100644 kernel/liveupdate/Makefile
 rename kernel/{ => liveupdate}/kexec_handover.c (80%)
 rename kernel/{ => liveupdate}/kexec_handover_debug.c (100%)
 create mode 100644 kernel/liveupdate/kexec_handover_debugfs.c
 create mode 100644 kernel/liveupdate/kexec_handover_internal.h


base-commit: 72fb0170ef1f45addf726319c52a0562b6913707
-- 
2.51.1.821.gb6fe4d2222-goog