Re: [PATCH v6 0/2] kexec: keep the next kernel off hardware-poisoned pages

[Bradley Morgan]

On 12 August 2026 12:31:50 BST, Breno Leitao <leitao at debian.org> wrote:
>Memory failures are common enough on large fleets that kexec regularly
>lands the next kernel on a frame the memory failure subsystem has already
>marked bad. Patch 2 teaches the segment placement to avoid those frames.
>
>Patch 1 is a prerequisite. locate_mem_hole_top_down() walks candidates
>downwards without ever checking that the subtraction stays above zero, so
>the walk can wrap and report success with a destination outside of RAM.
>Patch 2 adds one more downward step to that loop, so the bug is fixed
>first and both patches rely on the same bail-out.
>
>Signed-off-by: Breno Leitao <leitao at debian.org>
>---
>Changes in v6:
>- Split the pre-existing top-down underflow out into its own patch, and
>  drop the "if (poison < kbuf->memsz)" guard from the hwpoison hunk now
>  that the loop bail-out covers it. (Mike Rapoport, Sashiko)
>- Reword the changelog: the MCE comes from reading the poison back, not
>  from the relocation copy writing it, and the placement paragraphs read
>  better split up. (Mike Rapoport)
>- Move cond_resched() after the struct page dereference, so the scan does
>  not yield between pfn_to_online_page() and is_page_hwpoison().
>  (Pratyush Yadav, Sashiko)
>- Keep cond_resched() per pfn rather than batching it. (Kiryl Shutsemau,
>  Rik van Riel)
>- Link to v5: https://patch.msgid.link/20260810-kexec_posioned-v5-1-95e1b5e2e656@debian.org

This is a two patch series with one patch, why?


>
>Changes in v5:
>- Return -EHWPOISON instead of -EADDRNOTAVAIL
>- Leverage is_page_hwpoison() instead of per-page check
>- Link to v4: https://patch.msgid.link/20260807-kexec_posioned-v4-1-70d57f14625d@debian.org
>
>Changes in v4:
>- Anchor the top-down hole finder on the first poisoned page in the
>  window and the bottom-up one on the last, so each jumps clear of the
>  poison in one step. New range_first_hwpoison(). (Kiryl Shutsemau)
>- Count a poisoned hugetlb folio in full: the flag lives on the folio,
>  not on the subpages, so the per-pfn scan missed poisoned tail pages.
>  (Kiryl Shutsemau)
>- Link to v3: https://patch.msgid.link/20260803-kexec_posioned-v3-1-83aa6ede0351@debian.org
>
>Changes in v3:
>- Return the address of the last poisoned page in the range, or
>  PHYS_ADDR_MAX when it is clean, instead of a bool plus an output
>  parameter. Renamed to range_last_hwpoison(). (Pratyush Yadav)
>- Add cond_resched() to the scan loop, as a segment can span half of
>  memory. (Sashiko)
>- Link to v2: https://patch.msgid.link/20260730-kexec_posioned-v2-1-f92d18551f64@debian.org
>
>Changes in v2:
>- Change from pfn_to_page() to pfn_to_online_page(). (Miaohe Lin)
>- Return the poisoned address once we find a hit, to avoid the O(n^2)
>  rescan. (Sashiko)
>- Link to v1: https://patch.msgid.link/20260728-kexec_posioned-v1-1-160c81d180fe@debian.org
>
>To: Andrew Morton <akpm at linux-foundation.org>
>To: David Hildenbrand <david at kernel.org>
>To: Lorenzo Stoakes <ljs at kernel.org>
>To: "Liam R. Howlett" <liam at infradead.org>
>To: Vlastimil Babka <vbabka at kernel.org>
>To: Mike Rapoport <rppt at kernel.org>
>To: Suren Baghdasaryan <surenb at google.com>
>To: Michal Hocko <mhocko at suse.com>
>To: Baoquan He <baoquan.he at linux.dev>
>To: Pasha Tatashin <pasha.tatashin at soleen.com>
>To: Pratyush Yadav <pratyush at kernel.org>
>To: Miaohe Lin <linmiaohe at huawei.com>
>To: Naoya Horiguchi <nao.horiguchi at gmail.com>
>Cc: linux-mm at kvack.org
>Cc: linux-kernel at vger.kernel.org
>Cc: kexec at lists.infradead.org
>Cc: rmikey at meta.com
>Cc: riel at surriel.com
>
>---
>Breno Leitao (2):
>      kexec_file: stop the top-down search before it underflows
>      kexec: keep the next kernel off hardware-poisoned pages
>
> include/linux/mm.h  | 14 ++++++++++++++
> kernel/kexec_core.c | 10 ++++++++++
> kernel/kexec_file.c | 20 +++++++++++++++++++-
> mm/memory-failure.c | 40 ++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 83 insertions(+), 1 deletion(-)
>---
>base-commit: c5e32e86ca02b003f86e095d379b38148999293d
>change-id: 20260727-kexec_posioned-72bb0a4143a0
>
>Best regards,
>--  
>Breno Leitao <leitao at debian.org>
>
>

Thanks!