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 6F1F73385BE; Mon, 27 Apr 2026 15:40:43 +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=1777304443; cv=none; b=OmpsdKgaeP/eNhA5MXaardK3zAddNMDAflVJPBTvYFv6Ygvp7D87qaUEK+bpCuGtI2P8tPbystxYNJP63yvZNhFO3wXk2+5JP/gdaRYqTL1U8EQVALbkg4IdsFKNaOUMQqYQeVTTmT1uxIZoBOikR7dz88mWkghM0vdNQNLOhf4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777304443; c=relaxed/simple; bh=c8ztL5UJrnKIx/gGq3C03wQiSe/tIOB3pUyZvRG+qEY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=SzIZGs+ZytAdWBm/yUvwn6qGYOeCnODBdWGNJeTti2e27WoESR1dByFkdqapwkrSmqdavbxVQb7S1E/moq71XP8MejtxW+ahQ00ntW61godtjHEJ+ijEFBzUnnQRBI4Ni3oeN5U+l2b8nIKNFPG3HBtObovSULN3XYKLZz5y8oY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mUWPmibx; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mUWPmibx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 32E84C19425; Mon, 27 Apr 2026 15:40:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777304443; bh=c8ztL5UJrnKIx/gGq3C03wQiSe/tIOB3pUyZvRG+qEY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=mUWPmibx6XGiHzbFEs7Q45k7h6/CeaHuAHbjRnQNotmsWKgFaOgF4Thugm9BA15E4 ssViSqsIK/A49KyM3PkCBLRtdA39SeG4grMveEhu0+Vq0DxpA5lBl1M5QAK4X6AHqt tSwxoyLHsmqdi/VuI1u6Feu8i9f3ScduyyuVzt2t9bHgzHfCl4PiLDqSyPVG0BiFK1 O7pTqpztSboqGVB09gRretT2FHBO6LAXojisdHqCAH3y/TN8T4lSJr4Mh1G9dOvpYX nEFw4+p/i7tSKDH6opba6CZB7xqiGQbbnLpT69yCQ5KBlDgik3xfb6ZWFc9VhvNWi8 gHjPQimeD6xgw== Message-ID: Date: Mon, 27 Apr 2026 17:40:34 +0200 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 4/7] mm: add page consistency checker implementation To: Sasha Levin Cc: Pasha Tatashin , akpm@linux-foundation.org, corbet@lwn.net, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, skhan@linuxfoundation.org, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Sasha Levin , Sanif Veeras , "Claude:claude-opus-4-7" References: <20260424140056.2094777-1-sashal@kernel.org> <20260424140056.2094777-5-sashal@kernel.org> <4b961a07-b72d-4c8a-ab49-23f61ed12b53@kernel.org> <12985b32-88b3-47ab-8292-2e0ec6f5fbae@kernel.org> <3146ebcf-5649-44a7-aa21-163bf404c42b@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit >>> >>> For something like a datacenter deployment I'd agree with you - the odds are >>> too low to care. For an unsupervised self driving vehicle, where there's no >>> human (locally or remotely) available to take over, I'd like the odds to be as >>> low as possible :) >> >> I thought that people usually use special RT OSes (with proven logic etc) for >> any safety-related systems. Using Linux on the core safety system sounds ... >> scary. > > RT OSes are indeed the current approach. > > s/scary/exciting ;) Not so exciting for the passengers ;) > >> But, I'd expect corruption of other data (user pages? page tables?) a much >> bigger problem than page al locator metdata? What am I missing that this here is >> -- in context of the bigger problems there -- a thing we particularly care about? > > You are very correct! The allocator work was fairly standalone, so it was an > easy first project to tackle. But in general, wouldn't we just expect ECC memory to give us an MCE, so we can detect what was corrupted and act accordingly? That's how it usually works: hw detects a memory corruption and injects an MCE. We detect that we corrupted memmap state and kill the kernel. Why does ECC not help here? > > In general, the approach depends on what we're trying to defend from: > > 1. bugs: an ASI-like MMU enforced "context" system. > 2. physics: just like in most other areas - lots of redundancy. For example, > consider redundant variables in safety critical code which exists as two > copies: var_v1 = value and var_v2 = value XOR mask. When accessing them, read > both copies, XOR the second back, compare. > > There were a few sessions back in LPC about this. Here's the one from Bryan > Huntsman which gives a good overview: > https://www.youtube.com/watch?v=ie_ClBCed94 Thanks, but I fundamentally don't understand how RAS capabilities interact here? We have mm/memory-failure.c for a reason :) -- Cheers, David