[PATCH v7 0/6] mm/memory-failure: add panic option for unrecoverable pages

[Breno Leitao <leitao@debian.org>]

A multi-bit ECC error on a kernel-owned page that the memory failure
handler cannot recover is currently swallowed: PG_hwpoison is set, the
event is logged, and the kernel keeps running.  The corrupted memory
remains accessible to the kernel and either drives silent data
corruption or surfaces seconds-to-minutes later as an apparently
unrelated crash.  In a large fleet that delayed, unattributable crash
turns into significant engineering effort to root-cause; in a kdump
configuration, by the time the crash happens the original error
context (faulting PFN, MCE/GHES record, page state) is long gone.

This series adds an opt-in sysctl,
vm.panic_on_unrecoverable_memory_failure, that converts an
unrecoverable kernel-page hwpoison event into an immediate panic with
a clean dmesg/vmcore that still contains the original failure
context.  The default is disabled so existing workloads see no
change.

Signed-off-by: Breno Leitao <leitao@debian.org>
---
Changes in v7:
- Move the PG_reserved / unhandlable-kernel-page classification into
  get_any_page() and surface it via -ENOTRECOVERABLE, per David
  Hildenbrand's and Lance Yang's review of v6.  This drops the
  is_reserved snapshot in memory_failure() and the mf_get_page_status
  enum / out-parameter introduced in v6.
- Restructure the post-call branch in memory_failure() as a switch
  over the get_hwpoison_page() return code (David).
- Drop the "reserved" qualifier from the MF_MSG_KERNEL label and the
  matching tracepoint string; the enum now covers both PG_reserved
  pages and other unhandlable kernel pages.
- Squash the former patches 1/4 ("MF_MSG_KERNEL for reserved pages")
  and 2/4 ("classify get_any_page() failures by reason") into a
  single classification patch; the series is now 3 patches.
- Simplify panic_on_unrecoverable_mf() to a single return statement
  (David).
- Link to v6: https://patch.msgid.link/20260511-ecc_panic-v6-0-183012ba7d4b@debian.org

Changes in v6:
- Dropped the selftest given the value was not clear
- Get the status of the failure from get_any_page()
- Small nits from different people/AIs.
- Link to v5: https://patch.msgid.link/20260424-ecc_panic-v5-0-a35f4b50425c@debian.org

Changes in v5:
- Add vm.panic_on_unrecoverable_memory_failure sysctl to panic on
  unrecoverable kernel page hwpoison events (reserved pages, refcount-0
  non-buddy pages, unknown state), with a recheck to avoid racing with
  concurrent buddy allocations. (Miaohe)
- Distinguish reserved pages as MF_MSG_KERNEL in memory_failure(),
  document the new sysctl in Documentation/admin-guide/sysctl/vm.rst,
  and add a selftest verifying SIGBUS recovery on userspace pages still
  works when the sysctl is enabled. (Miaohe)
- Added a selftest
- Link to v4:
  https://patch.msgid.link/20260415-ecc_panic-v4-0-2d0277f8f601@debian.org

Changes in v4:
- Drop CONFIG_BOOTPARAM_MEMORY_FAILURE_PANIC kernel configuration option.
- Split the reserved page classification (MF_MSG_KERNEL) into its own
  patch, separate from the panic mechanism.
- Document why the buddy allocator TOCTOU race (between
  get_hwpoison_page() and is_free_buddy_page()) cannot cause false
  positives: PG_hwpoison is set beforehand and check_new_page() in the
  page allocator rejects hwpoisoned pages.
- Document the narrow LRU isolation race window for MF_MSG_UNKNOWN and
  its mitigation via identify_page_state()'s two-pass design.
- Explicitly document why MF_MSG_GET_HWPOISON is excluded from the
  panic conditions (shared path with transient races and non-reserved
  kernel memory).
- Link to v3: https://patch.msgid.link/20260413-ecc_panic-v3-0-1dcbb2f12bc4@debian.org

Changes in v3:
- Rename is_unrecoverable_memory_failure() to panic_on_unrecoverable_mf()
  as suggested by maintainer.
- Add CONFIG_BOOTPARAM_MEMORY_FAILURE_PANIC kernel configuration option,
  similar to CONFIG_BOOTPARAM_HARDLOCKUP_PANIC.
- Add documentation for the sysctl and CONFIG option.
- Add code comments documenting the panic condition design rationale and
  how the retry mechanism mitigates false positives from buddy allocator
  races.
- Link to v2: https://patch.msgid.link/20260331-ecc_panic-v2-0-9e40d0f64f7a@debian.org

Changes in v2:
- Panic on MF_MSG_KERNEL, MF_MSG_KERNEL_HIGH_ORDER and MF_MSG_UNKNOWN
  instead of MF_MSG_GET_HWPOISON.
- Report MF_MSG_KERNEL for reserved pages when get_hwpoison_page() fails
  instead of MF_MSG_GET_HWPOISON.
- Link to v1: https://patch.msgid.link/20260323-ecc_panic-v1-0-72a1921726c5@debian.org

To: Miaohe Lin <linmiaohe@huawei.com>
To: Naoya Horiguchi <nao.horiguchi@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>
To: Steven Rostedt <rostedt@goodmis.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Jonathan Corbet <corbet@lwn.net>
To: Shuah Khan <skhan@linuxfoundation.org>
To: David Hildenbrand <david@kernel.org>
To: Lorenzo Stoakes <ljs@kernel.org>
To: "Liam R. Howlett" <liam@infradead.org>
To: Vlastimil Babka <vbabka@kernel.org>
To: Mike Rapoport <rppt@kernel.org>
To: Suren Baghdasaryan <surenb@google.com>
To: Michal Hocko <mhocko@suse.com>
To: Shuah Khan <shuah@kernel.org>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-trace-kernel@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org

---
Breno Leitao (6):
      mm/memory-failure: drop dead error_states[] entry for reserved pages
      mm/memory-failure: surface unhandlable kernel pages as -ENOTRECOVERABLE
      mm/memory-failure: report MF_MSG_KERNEL for unrecoverable kernel pages
      mm/memory-failure: short-circuit PG_reserved before get_hwpoison_page()
      mm/memory-failure: add panic option for unrecoverable pages
      Documentation: document panic_on_unrecoverable_memory_failure sysctl

 Documentation/admin-guide/sysctl/vm.rst | 80 +++++++++++++++++++++++++++++++
 mm/memory-failure.c                     | 85 +++++++++++++++++++++++++--------
 2 files changed, 146 insertions(+), 19 deletions(-)
---
base-commit: e98d21c170b01ddef366f023bbfcf6b31509fa83
change-id: 20260323-ecc_panic-4e473b83087c

Best regards,
--  
Breno Leitao <leitao@debian.org>