From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from stravinsky.debian.org (stravinsky.debian.org [82.195.75.108]) (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 C18CE37DEBE; Fri, 26 Jun 2026 15:34:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=82.195.75.108 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782488051; cv=none; b=U2HeTknuus1yPSFzyWXf0NJWUqEfyFekcjyYaNwqiIc4m4Bckqw8FpFJjchKYamUUFQa2b/Zl3uvixyZ71J3BsD5jEM2Aq+InDtrQsPOFZtwVNTADzepCy96rSS2TfTlM0q4rbAr9Bem3zYcWtiHUVgcQqmP5Hmq9K9sITnUX7c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782488051; c=relaxed/simple; bh=msoDLvFqwsOJsYCzBq/Fp8NcqXTHSLhr0v0oqz9cZZ0=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=c3QCN+FrJascC4ECqzva7M0ERXsWoadb0UCQlMiLyGeJ8x9/E97KedizkwZiDa73smv5/PK8x9q+zgwafq0fGAAz6jQwCHW/ewvMcgDYE4gODcU84f6tPBmDTMapCBz96dYYuqn0RAg/pgPyfsr4EOeP6KMxDCZNuAOMapPWJGo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=debian.org; spf=pass smtp.mailfrom=debian.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b=TwUXR5E9; arc=none smtp.client-ip=82.195.75.108 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=debian.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=debian.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b="TwUXR5E9" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=debian.org; s=smtpauto.stravinsky; h=X-Debian-User:Cc:To:In-Reply-To:References: Message-Id:Content-Transfer-Encoding:Content-Type:MIME-Version:Subject:Date: From:Reply-To:Content-ID:Content-Description; bh=f+riptiA6r5Y/PNxg2RAlIaqa1a8ryBQwwolMCsPfZU=; b=TwUXR5E9/K37R5jz0A2WuTPfbL Dsobixxr4sNOLkxi+2HZ1OCS7KvmFJOiRPVsi7kDxsSwVi7SvRQNaKIyJmxM7aCBJJDO05ZrhOmfr Tkq3TBZOMCS83htptyCNWALmAlvNRMCdD/N7ARfZ580aEZBBvGzRAI6y8zTn7o6nlp7JyJC4/RSEa G7UOu0m+8QjuQxsNwctvCZNfXs7YFtQVTIkTo2G6ROO2BzkTdypuldIS5yxWvPpWgv3YatDynbAi/ g1A54zXsj24o9cp0JxIhSYZoC4G3WFKe3CObnfBee87VvkJSNPc1abUNIiV2IpM+d2MpntQdstXzH 2PWsV1Yw==; Received: from authenticated-user by stravinsky.debian.org with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.96) (envelope-from ) id 1wd8Z5-0044Em-0f; Fri, 26 Jun 2026 15:33:59 +0000 From: Breno Leitao Date: Fri, 26 Jun 2026 08:33:19 -0700 Subject: [PATCH v10 5/6] Documentation: document panic_on_unrecoverable_memory_failure sysctl Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Message-Id: <20260626-ecc_panic-v10-5-6dacb8ad024d@debian.org> References: <20260626-ecc_panic-v10-0-6dacb8ad024d@debian.org> In-Reply-To: <20260626-ecc_panic-v10-0-6dacb8ad024d@debian.org> To: Miaohe Lin , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Naoya Horiguchi , Jonathan Corbet , Shuah Khan , "Liam R. Howlett" , lance.yang@linux.dev, Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , "Liam R. Howlett" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, Breno Leitao , linux-trace-kernel@vger.kernel.org, kernel-team@meta.com X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=4818; i=leitao@debian.org; h=from:subject:message-id; bh=msoDLvFqwsOJsYCzBq/Fp8NcqXTHSLhr0v0oqz9cZZ0=; b=owEBbQKS/ZANAwAIATWjk5/8eHdtAcsmYgBqPpvFGxxyKT9/sgwOOS0p+wzSQP+2uxPNzEPhh B8C+2sz0neJAjMEAAEIAB0WIQSshTmm6PRnAspKQ5s1o5Of/Hh3bQUCaj6bxQAKCRA1o5Of/Hh3 bdfYD/9Q3Rl+4JzL2jM/faeOug7+fuPvmgpElU1400RuLNC0KARD/bUAd6RtRjjjCka/eLoHDwP aKRf6ZUyL0HzrTZ5xoP3yfrrFiM1OOXW33F24m5WViPF19uPOYQHRTcFWE3/gWFzUhd0MkapvIu bzH9CP5xaKBycNQrvdJ6ryToVS+DcYhGnu0SIA9eBQ1dYXl6//rKAJ75cW24T+Y/3Jph/Et1QEn K4Pplpm6urFSaiPabT64tvILB3guoQPj0MW0lu5r5TKvSLAJUZYNCsuGZ9CFxMYfQ+lE0615NGT jh+Y5GlMyBH2/OUYd3yywqV927hh1pkA10nAzxdRSsSXXYL0I1hpk8UoZDX/6XGvjQRTKFNY305 0crU4ZE+7gxzwuIipO0HirQI1j3lvYOxRaLMptDwa/CD6id8/kj5cH+B4tgV78LLWBbypkbf2mm mVoXZaiJMP8p0LdebVWsUvszcOAOXElEW4WFRy/BnxR0sNPzJpZ1iBnlf5kkXBJoQxUd1zf9rsq IyZifZaNUDQpGhNdeoCPrK+z7ZGsY3tV3moKC3/81tPAoShFSjmXW/ZAbq+LcmM+qn+uqs0Y4dC lYvGy1Z9oYkWg9sjW3A4BRWg+m21JYo3ca7BSt0OSWGGtfD6ugSzqHl9eCwTeNn6oOCtlLLmuGx yVpTpqOz7c9NtIw== X-Developer-Key: i=leitao@debian.org; a=openpgp; fpr=AC8539A6E8F46702CA4A439B35A3939FFC78776D X-Debian-User: leitao Add documentation for the new vm.panic_on_unrecoverable_memory_failure sysctl, describing which failures trigger a panic (kernel-owned pages the handler cannot recover) and which are intentionally left out (transient allocator races and unclassified pages). Signed-off-by: Breno Leitao --- Documentation/admin-guide/sysctl/vm.rst | 80 +++++++++++++++++++++++++++++++++ 1 file changed, 80 insertions(+) diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst index b9b0c218bfb44..22cc54cac3b21 100644 --- a/Documentation/admin-guide/sysctl/vm.rst +++ b/Documentation/admin-guide/sysctl/vm.rst @@ -67,6 +67,7 @@ Currently, these files are in /proc/sys/vm: - page-cluster - page_lock_unfairness - panic_on_oom +- panic_on_unrecoverable_memory_failure - percpu_pagelist_high_fraction - stat_interval - stat_refresh @@ -925,6 +926,85 @@ panic_on_oom=2+kdump gives you very strong tool to investigate 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 memory failure events +hitting kernel-owned pages that the handler cannot recover: +``PageReserved`` (firmware reservations, kernel image, vDSO, zero +page, and similar memblock-reserved regions), ``PageSlab``, +``PageTable``, and ``PageLargeKmalloc``. These are owned by the +kernel and the memory failure handler cannot reliably evict their +contents. + +Other unrecoverable kernel-owned populations (vmalloc allocations, +kernel stack pages, ...) are not currently covered because the +handler has no page-type signal that distinguishes them from a +userspace folio temporarily off the LRU during migration or +compaction. Such pages still go through the standard +MF_MSG_GET_HWPOISON path: ``PG_hwpoison`` is set on them and a +delayed crash on the next access remains possible. Coverage may +grow as the handler gains stronger kernel-ownership signals. + +Recoverable failure paths are also intentionally left out: in-flight +buddy allocations and other transient races with the page allocator +can reach the same diagnostic, and panicking on them would risk +killing the box for a page destined for userspace where the standard +SIGBUS recovery path applies. Pages whose state could not be +classified at all are not covered either, since an unknown state is +not a sound basis for a panic decision. + +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 ============================= -- 2.53.0-Meta