linux-kernel - [RFC v1 0/4] Make KHO Stateless

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Message-ID: <20250917025019.1585041-1-jasonmiu@google.com>
Date: Tue, 16 Sep 2025 19:50:15 -0700
From: Jason Miu <jasonmiu@...gle.com>
To: Alexander Graf <graf@...zon.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Baoquan He <bhe@...hat.com>, Changyuan Lyu <changyuanl@...gle.com>, 
	David Matlack <dmatlack@...gle.com>, David Rientjes <rientjes@...gle.com>, 
	Jason Gunthorpe <jgg@...dia.com>, Jason Miu <jasonmiu@...gle.com>, 
	Joel Granados <joel.granados@...nel.org>, Marcos Paulo de Souza <mpdesouza@...e.com>, 
	Mario Limonciello <mario.limonciello@....com>, Mike Rapoport <rppt@...nel.org>, 
	Pasha Tatashin <pasha.tatashin@...een.com>, Petr Mladek <pmladek@...e.com>, 
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>, Steven Chen <chenste@...ux.microsoft.com>, 
	Yan Zhao <yan.y.zhao@...el.com>, kexec@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [RFC v1 0/4] Make KHO Stateless

This series transitions KHO from an xarray-based metadata tracking
system with serialization to using page table like data structures
that can be passed directly to the next kernel.

The key motivations for this change are to:
- Eliminate the need for data serialization before kexec.
- Remove the former KHO state machine by deprecating the finalize
  and abort states.
- Pass preservation metadata more directly to the next kernel via the FDT.

The new approach uses a per-order page table structure (kho_order_table,
kho_page_table, kho_bitmap_table) to mark preserved pages. The physical
address of the root `kho_order_table` is passed in the FDT, allowing the
next kernel to reconstruct the preserved memory map.

The series includes the following changes:
1.  Introduce the KHO page table data structures.
2.  Adopt the KHO page tables, remove the xarray-based tracking and
    the serialization/finalization code.
3.  Update memblock to use direct KHO API calls, and adjust KHO FDT
    completion timing.
4.  Remove the KHO notifier system infrastructure.
        

Jason Miu (4):
  kho: Introduce KHO page table data structures
  kho: Adopt KHO page tables and remove serialization
  memblock: Remove KHO notifier usage
  kho: Remove notifier system infrastructure

 include/linux/kexec_handover.h |  44 +-
 kernel/kexec_core.c            |   4 +
 kernel/kexec_handover.c        | 821 ++++++++++++++++-----------------
 kernel/kexec_internal.h        |   2 +
 mm/memblock.c                  |  46 +-
 5 files changed, 404 insertions(+), 513 deletions(-)

-- 
2.51.0.384.g4c02a37b29-goog