From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 64CC3C6FA83 for ; Mon, 12 Sep 2022 20:23:28 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BE1648D0001; Mon, 12 Sep 2022 16:23:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B90E96B0072; Mon, 12 Sep 2022 16:23:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A58C58D0001; Mon, 12 Sep 2022 16:23:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 94AD06B0071 for ; Mon, 12 Sep 2022 16:23:27 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 6D9E8A1053 for ; Mon, 12 Sep 2022 20:23:27 +0000 (UTC) X-FDA: 79904558454.28.35FCA85 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf22.hostedemail.com (Postfix) with ESMTP id 08F45C00BF for ; Mon, 12 Sep 2022 20:23:25 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 95E7DB80C9E; Mon, 12 Sep 2022 20:23:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 29911C433D6; Mon, 12 Sep 2022 20:23:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1663014203; bh=V7XKrZJImH3ItQ7EvPsT2qdGqMPYz4GDAX5yuckn2rQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=qNIPHzmgHprhHCZZQt1KEnDXQwoNzGJBbNmWaHY2Hyr6Y+pFN5ysScUAKnVVLAUct 1DqNhpDuDZBzf4Gc466iorybnr/i3RCihkAWQY2BIgOCAKTKLIN4Q6qjJ9ipSQvQuh YF5asvUxcEqMYSo/t/7k5gSY6zwv4DImn1wpmf5k= Date: Mon, 12 Sep 2022 13:23:22 -0700 From: Andrew Morton To: Pasha Tatashin Cc: corbet@lwn.net, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, rick.p.edgecombe@intel.com Subject: Re: [PATCH 0/3] page table check default to warn instead of panic Message-Id: <20220912132322.7c486c40c6acf8eec0785c87@linux-foundation.org> In-Reply-To: <20220911095923.3614387-1-pasha.tatashin@soleen.com> References: <20220911095923.3614387-1-pasha.tatashin@soleen.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=qNIPHzmg; spf=pass (imf22.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1663014206; a=rsa-sha256; cv=none; b=ZMa/ApR/sdXJbmhngK+U8CEqLJLs4KzyNoVd9ZtKGjkL8yBXjkxIuwKWlQPZ4GWar/rqvL zoRws643LJ4/UypSfyytK+F2300HwieSmmu1DqGtZVgh7eU0KQ1pgHuTV9QLj97uXv1Twm 4FnOmi1sgN3rPGyvXao5P910rK1u19o= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1663014206; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=E38x4yUqfl2eeIhpf2Rrmm5UtzhqSN0OrjVUrQ7btPI=; b=kjwjvk3bHErekpWo1dz/xSZH2HbCkbliaNoodyXeZ7q7E4YKeK+KOBgCIxE3dRCK8dz1Gl I6eDIpdtSCT0MayGdnxts8AQpJE9sIc2IUGx7ImMVpuATOa/hVlKouVhXr5v9JxPBoLHLQ XOXh38mO5s+D5Qbu1vsowV+NaV/IUZE= X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 08F45C00BF X-Rspam-User: Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=qNIPHzmg; spf=pass (imf22.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-Stat-Signature: k4t3bor7z97hjhm4k3pgcqybbi98izsh X-HE-Tag: 1663014205-444784 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun, 11 Sep 2022 09:59:20 +0000 Pasha Tatashin wrote: > From: Pasha Tatashin > > Page table check when detects errors panics the kernel. Let instead, > print a warning, and panic only when specifically requested via kernel > parameter: > > page_table_check=panic > > The discussion about using panic vs. warn is here: > https://lore.kernel.org/linux-mm/20220902232732.12358-1-rick.p.edgecombe@intel.com The changelog doesn't actually describe the reason for making this change. Somebody obviously wants pagetable check errors to no longer panic the kernel, but why?? (The same can be said of the [2/3] changelog). Also, should we be changing the default? People who like the panic will get a big surprise when they find out that they should have added a kernel parameter to get the old behaviour back. It would be less disruptive to default to panic unless page_table_check=warn was added. If there's a solid reason for changing the default, it should be changelogged. And if that reason is generally agreed to, perhaps the kernel should print a warning at boot if neither page_table_check=panic nor page_table_check=warn were provided. To tell people that the default has been changed.