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 X-Spam-Level: X-Spam-Status: No, score=-12.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8725FC433C1 for ; Thu, 25 Mar 2021 19:29:27 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 039E661A31 for ; Thu, 25 Mar 2021 19:29:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 039E661A31 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8396B6B006C; Thu, 25 Mar 2021 15:29:26 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 811036B006E; Thu, 25 Mar 2021 15:29:26 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6FF656B0070; Thu, 25 Mar 2021 15:29:26 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0001.hostedemail.com [216.40.44.1]) by kanga.kvack.org (Postfix) with ESMTP id 55D056B006C for ; Thu, 25 Mar 2021 15:29:26 -0400 (EDT) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 1A9A9C5B7 for ; Thu, 25 Mar 2021 19:29:26 +0000 (UTC) X-FDA: 77959385532.06.4277D3D Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf21.hostedemail.com (Postfix) with ESMTP id 6BA0CE000252 for ; Thu, 25 Mar 2021 19:29:24 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id CB40761A26; Thu, 25 Mar 2021 19:29:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1616700564; bh=mP2NouLDus9q94+GA0gdi+r3nEQsG5iXHcIixE8bd94=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=hC8YAnn8yxndfhJ9e1Cxb8w9k0Fkk54vFTDaFZ58BLD2VK2opByIRzjm/+MFra0hP XOKroJa5ZZNtc05/h4eJDzyhAswNHLa/+aB9k7VGeCN+OffuoaS/oJsfxlMsnYJ4cw ALQdfLkphsF9Oe0D/NVUVAq1ausScmmRY9DV3H9B0AhSzr2SFUuHaGYIX7aXKVINlt lAVaHObSdO7pHnam+GRuBiE35yFr8snAC7dnNm5L/3p1q7CzwUGmA78XErDHkEAlHE vDB+DyoCv2rsnM8pz+50LI3k39PbKiiVhtXyMfyyCSTnli2bC1wHygX+oFpyCiOAIJ IM26YWjJ/AdYg== Date: Thu, 25 Mar 2021 19:29:19 +0000 From: Will Deacon To: Dmitry Vyukov Cc: syzbot , kernel-team@android.com, Andrew Morton , LKML , Linux-MM , syzkaller-bugs , Linux ARM , syzkaller Subject: Re: [syzbot] BUG: soft lockup in do_wp_page (4) Message-ID: <20210325192918.GB16123@willie-the-truck> References: <000000000000ce4c9505bdd4a48f@google.com> <20210325182046.GA15860@willie-the-truck> <20210325191006.GE15860@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 6BA0CE000252 X-Stat-Signature: n6mufd1rbsshus45fahk9ui5m9damq5h Received-SPF: none (kernel.org>: No applicable sender policy available) receiver=imf21; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1616700564-558092 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 Thu, Mar 25, 2021 at 08:24:53PM +0100, Dmitry Vyukov wrote: > On Thu, Mar 25, 2021 at 8:10 PM Will Deacon wrote: > > On Thu, Mar 25, 2021 at 07:34:54PM +0100, Dmitry Vyukov wrote: > > > On Thu, Mar 25, 2021 at 7:20 PM Will Deacon wrote: > > > > On Thu, Mar 18, 2021 at 08:34:16PM +0100, Dmitry Vyukov wrote: > > > > > On Thu, Mar 18, 2021 at 8:31 PM syzbot > > > > > wrote: > > > > > commit cae118b6acc309539b33339e846cbb19187c164c > > > > > Author: Will Deacon > > > > > Date: Wed Mar 3 13:49:27 2021 +0000 > > > > > arm64: Drop support for CMDLINE_EXTEND > > > > > > > > > > syzbot passes lots of critical things in CONFIG_CMDLINE: > > > > > https://github.com/google/syzkaller/blob/c3c81c94865791469d376eba84f4a2d7763d3f71/dashboard/config/linux/upstream-arm64-kasan.config#L495 > > > > > but also wants the bootloader args to be appended. > > > > > What is the way to do it now? > > > > > > > > For now, there isn't a way to do it with CONFIG_CMDLINE, so I think you can > > > > either: > > > > > > > > * Revert my patch for your kernels > > > > * Pass the arguments via QEMU's -append option > > > > * Take a look at one of the series which should hopefully add this > > > > functionality back (but with well-defined semantics) [1] [2] > > > > > > Unfortunately none of these work for syzbot (and I assume other > > > testing environments). > > > > > > syzbot does not support custom patches by design: > > > http://bit.do/syzbot#no-custom-patches > > > As any testing system, it tests the official trees. > > > > > > It's not humans who start these VMs, so it's not as easy as changing > > > the command line after typing... > > > There is no support for passing args specifically to qemu, syzkaller > > > support not just qemu, so these things are specifically localized in > > > the config. Additionally there is an issue of communicating all these > > > scattered details to developers in bug reports. Currently syzbot > > > reports the kernel config and it as well captures command line. > > > > > > Could you revert the patch? Is there any point in removing the > > > currently supported feature before the new feature lands? > > > > Well, we only just merged it (in 5.10 I think?), and the semantics of the > > new version will be different, so I really don't see the value in supporting > > both (even worse, Android has its own implementation which is different > > again). The timeline was: we merged CMDLINE_EXTEND, then we noticed it was > > broken, my fixes were rejected, so we removed the feature rather than > > support the broken version. In the relatively small window while it was > > merged, syzbot started using it :( > > I didn't realize it was just introduced :) > We used CMDLINE_EXTEND on x86, and I looked for a similar option for > arm64 and found it. > > > So I really think the best bet is to wait until the patches are sorted out. > > I think Christophe is about to spin a new version, and I reviewed his last > > copy, so I don't see this being far off, > > If it's expected to be merged soon, let's wait. Thanks, and knowing that we have a keen user helps to prioritise the review :) Will