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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AA0BEC6FA8B for ; Mon, 12 Sep 2022 20:23:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229718AbiILUX2 (ORCPT ); Mon, 12 Sep 2022 16:23:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47656 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229538AbiILUX0 (ORCPT ); Mon, 12 Sep 2022 16:23:26 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F0E96481D9; Mon, 12 Sep 2022 13:23:25 -0700 (PDT) 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 9B3A8B80C68; 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.