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

[Mike Rapoport]

On Wed, Aug 19, 2026 at 03:23:04PM +0100, Bradley Morgan wrote:
> On 19 August 2026 10:36:17 BST, Mike Rapoport <rppt@xxxxxxxxxx> wrote:
> >On Wed, Aug 12, 2026 at 04:31:50AM -0700, Breno Leitao 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.
> >
> >I queued this for v7.4, the patches will appear in the liveupdate tree
> >after the merge window.
> > 
> 
> Ah, so it'll appear in a maintainers tree after MW?

Yes
 
> >> Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
> >> ---
> >> 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@xxxxxxxxxx
> >> 
> >> 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@xxxxxxxxxx
> >> 
> >> 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@xxxxxxxxxx
> >> 
> >> 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@xxxxxxxxxx
> >> 
> >> 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@xxxxxxxxxx
> >> 
> >> To: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> >> To: David Hildenbrand <david@xxxxxxxxxx>
> >> To: Lorenzo Stoakes <ljs@xxxxxxxxxx>
> >> To: "Liam R. Howlett" <liam@xxxxxxxxxxxxx>
> >> To: Vlastimil Babka <vbabka@xxxxxxxxxx>
> >> To: Mike Rapoport <rppt@xxxxxxxxxx>
> >> To: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> >> To: Michal Hocko <mhocko@xxxxxxxx>
> >> To: Baoquan He <baoquan.he@xxxxxxxxx>
> >> To: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
> >> To: Pratyush Yadav <pratyush@xxxxxxxxxx>
> >> To: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> >> To: Naoya Horiguchi <nao.horiguchi@xxxxxxxxx>
> >> Cc: linux-mm@xxxxxxxxx
> >> Cc: linux-kernel@xxxxxxxxxxxxxxx
> >> Cc: kexec@xxxxxxxxxxxxxxxxxxx
> >> Cc: rmikey@xxxxxxxx
> >> Cc: riel@xxxxxxxxxxx
> >> 
> >> ---
> >> 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@xxxxxxxxxx>
> >> 
> >
> >
> 
> Thanks!

-- 
Sincerely yours,
Mike.