From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DA74D34750B for ; Mon, 27 Apr 2026 16:00:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777305609; cv=none; b=n6bjHxBFJoH9itZ8ZOn+XLDiMsZFefMFDaP+fagYYLFCOkYCzu5VqxnNQLvGS1BrUfUwMUGBSt8WiPS0fyzvJyUrUO08cqVuH6+vmqfqwZjj8tzZiLi06UwC/cu7EoIbBntZiTbZjg+9iZecytwUCRa1r1ZadK7LRrutq0g0UTE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777305609; c=relaxed/simple; bh=IT/ZUIGgrC5Pmy+1qfTD3+DeHjae/oNLIWKouVVM1bo=; h=Date:To:From:Subject:Message-Id; b=P40MdWtH/vSvk0akaghsKhqu/4Nx0939PqfOawAXJw1/+4v0kSlew3DZopo6GFiNAvunU6OayULuhJ1bnYoEbz+ptJ9E1x0TBdRikwPH6eSuJvr5kljpXvB90x5xHmDI71tduyBrPwQZMnGCBIBOKbQuvRO3KiuQqBnQL8a2xr0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=t2SWxKir; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="t2SWxKir" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B25E1C19425; Mon, 27 Apr 2026 16:00:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1777305609; bh=IT/ZUIGgrC5Pmy+1qfTD3+DeHjae/oNLIWKouVVM1bo=; h=Date:To:From:Subject:From; b=t2SWxKirl1JMCl9ePW4gEa4XLaBsdHnnd+Ve3TeYMlFqvT0hrR4s4C4xINU7RP3Pl jzMuAH2Jjp/nZr55f9TdKTg27/uEMs5DIhj8eQssY7gYWDvZBYHr3UtgOTEwNwAUqb aso2m89gw+N/h+ec9e+Q9X3wTfaoeAUZhuAsZG1w= Date: Mon, 27 Apr 2026 09:00:09 -0700 To: mm-commits@vger.kernel.org,leitao@debian.org,akpm@linux-foundation.org From: Andrew Morton Subject: [to-be-updated] documentation-document-panic_on_unrecoverable_memory_failure-sysctl.patch removed from -mm tree Message-Id: <20260427160009.B25E1C19425@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: Documentation: document panic_on_unrecoverable_memory_failure sysctl has been removed from the -mm tree. Its filename was documentation-document-panic_on_unrecoverable_memory_failure-sysctl.patch This patch was dropped because an updated version will be issued ------------------------------------------------------ From: Breno Leitao Subject: Documentation: document panic_on_unrecoverable_memory_failure sysctl Date: Fri, 24 Apr 2026 05:24:01 -0700 Add documentation for the new vm.panic_on_unrecoverable_memory_failure sysctl, describing the three categories of failures that trigger a panic and noting which kernel page types are not yet covered. Link: https://lore.kernel.org/20260424-ecc_panic-v5-3-a35f4b50425c@debian.org Signed-off-by: Breno Leitao Cc: David Hildenbrand Cc: Jonathan Corbet Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Miaohe Lin Cc: Michal Hocko Cc: Mike Rapoport Cc: Naoya Horiguchi Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Lance Yang Signed-off-by: Andrew Morton --- Documentation/admin-guide/sysctl/vm.rst | 65 ++++++++++++++++++++++ 1 file changed, 65 insertions(+) --- a/Documentation/admin-guide/sysctl/vm.rst~documentation-document-panic_on_unrecoverable_memory_failure-sysctl +++ a/Documentation/admin-guide/sysctl/vm.rst @@ -67,6 +67,7 @@ Currently, these files are in /proc/sys/ - page-cluster - page_lock_unfairness - panic_on_oom +- panic_on_unrecoverable_memory_failure - percpu_pagelist_high_fraction - stat_interval - stat_refresh @@ -925,6 +926,70 @@ panic_on_oom=2+kdump gives you very stro why oom happens. You can get snapshot. +panic_on_unrecoverable_memory_failure +====================================== + +When a hardware memory error (e.g. multi-bit ECC) hits a kernel page +that cannot be recovered by the memory failure handler, the default +behaviour is to ignore the error and continue operation. This is +dangerous because the corrupted data remains accessible to the kernel, +risking silent data corruption or a delayed crash when the poisoned +memory is next accessed. + +When enabled, this sysctl triggers a panic on three categories of +unrecoverable failures: reserved kernel pages, non-buddy kernel pages +with zero refcount (e.g. tail pages of high-order allocations), and +pages whose state cannot be classified as recoverable. + +Note that some kernel page types — such as slab objects, vmalloc +allocations, kernel stacks, and page tables — share a failure path +with transient refcount races and are not currently covered by this +option. I.e, do not panic when not confident of the page status. + +For many environments it is preferable to panic immediately with a clean +crash dump that captures the original error context, rather than to +continue and face a random crash later whose cause is difficult to +diagnose. + +Use cases +--------- + +This option is most useful in environments where unattributed crashes +are expensive to debug or where data integrity must take precedence +over availability: + +* Large fleets, where multi-bit ECC errors on kernel pages are observed + regularly and post-mortem analysis of an unrelated downstream crash + (often seconds to minutes after the original error) consumes + significant engineering effort. + +* Systems configured with kdump, where panicking at the moment of the + hardware error produces a vmcore that still contains the faulting + address, the affected page state, and the originating MCE/GHES + record — context that is typically lost by the time a delayed crash + occurs. + +* High-availability clusters that rely on fast, deterministic node + failure for failover, and prefer an immediate panic over silent data + corruption propagating to replicas or persistent storage. + +* Kernel and platform developers reproducing hwpoison issues with + tools such as ``mce-inject`` or error-injection debugfs interfaces, + where panicking on the unrecoverable path makes regressions + immediately visible instead of surfacing as later, unrelated + failures. + += ===================================================================== +0 Try to continue operation (default). +1 Panic immediately. If the ``panic`` sysctl is also non-zero then the + machine will be rebooted. += ===================================================================== + +Example:: + + echo 1 > /proc/sys/vm/panic_on_unrecoverable_memory_failure + + percpu_pagelist_high_fraction ============================= _ Patches currently in -mm which might be from leitao@debian.org are selftests-mm-regression-test-for-panic_on_unrecoverable_memory_failure.patch mm-huge_memory-use-sysfs_match_string-in-defrag_store.patch mm-huge_memory-refactor-defrag_show-to-use-defrag_flags.patch mm-vmstat-spread-vmstat_update-requeue-across-the-stat-interval.patch