kho: add support for deferred struct page init [LWN.net]

From:		Michal Clapinski <mclapinski-AT-google.com>
To:		Evangelos Petrongonas <epetron-AT-amazon.de>, Pasha Tatashin <pasha.tatashin-AT-soleen.com>, Mike Rapoport <rppt-AT-kernel.org>, Pratyush Yadav <pratyush-AT-kernel.org>, Alexander Graf <graf-AT-amazon.com>, Samiullah Khawaja <skhawaja-AT-google.com>, kexec-AT-lists.infradead.org, linux-mm-AT-kvack.org
Subject:		[PATCH v9 0/3] kho: add support for deferred struct page init
Date:		Thu, 23 Apr 2026 14:25:35 +0200
Message-ID:		<20260423122538.140993-1-mclapinski@google.com>
Cc:		linux-kernel-AT-vger.kernel.org, Andrew Morton <akpm-AT-linux-foundation.org>, Vlastimil Babka <vbabka-AT-kernel.org>, Suren Baghdasaryan <surenb-AT-google.com>, Michal Hocko <mhocko-AT-suse.com>, Brendan Jackman <jackmanb-AT-google.com>, Johannes Weiner <hannes-AT-cmpxchg.org>, Zi Yan <ziy-AT-nvidia.com>, Michal Clapinski <mclapinski-AT-google.com>
Archive-link:		Article

When CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled, struct page
initialization is deferred to parallel kthreads that run later in
the boot process.

Currently, KHO is incompatible with DEFERRED.
This series fixes that incompatibility.
---
v9:
- moved init_pageblock_migratetype from memmap_init_reserved_range
  to __init_page_from_nid
- reduced number of ifdefs
- new commit to test this feature
v8:
- moved overriding the migratetype from init_pageblock_migratetype
  to callsites
v7:
- reimplemented the initialization of kho scratch again
v6:
- reimplemented the initialization of kho scratch
v5:
- rebased
v4:
- added a new commit to fix deferred init of kho scratch
- switched to ulong when refering to pfn
v3:
- changed commit msg
- don't invoke early_pfn_to_nid if CONFIG_DEFERRED_STRUCT_PAGE_INIT=n
v2:
- updated a comment

I took Evangelos's test code:
https://git.infradead.org/?p=users/vpetrog/linux.git;a=sh...
and then modified it to this monster test that does 2 allocations:
at core_initcall (early) and at module_init (late). Then kexec, then
2 more allocations at these points, then restore the original 2, then
kexec, then restore the other 2. Basically I test preservation of early
and late allocation both on cold and on warm boot.
Tested it both with and without DEFERRED.
https://github.com/mclapinski/linux/commits/deferred_test/

This patch probably doesn't apply onto anything currently.
It's based on mm-new with
"memblock: move reserve_bootmem_range() to memblock.c and make it static"
cherrypicked from rppt/memblock.

Evangelos Petrongonas (1):
  kho: make preserved pages compatible with deferred struct page init

Michal Clapinski (2):
  kho: fix deferred initialization of scratch areas
  selftests: kho: test with deferred struct page init

 include/linux/memblock.h              | 21 +++++++++-
 kernel/liveupdate/Kconfig             |  2 -
 kernel/liveupdate/kexec_handover.c    | 52 ++++++++++++-------------
 mm/memblock.c                         | 56 +++++++++++----------------
 mm/mm_init.c                          | 30 +++++++-------
 tools/testing/selftests/kho/vmtest.sh |  4 ++
 6 files changed, 88 insertions(+), 77 deletions(-)

-- 
2.54.0.rc2.533.g4f5dca5207-goog