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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 78F17C433E0 for ; Mon, 1 Feb 2021 18:58:19 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E2A2264DA8 for ; Mon, 1 Feb 2021 18:58:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E2A2264DA8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 61E656B006C; Mon, 1 Feb 2021 13:58:18 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 5CE8A6B006E; Mon, 1 Feb 2021 13:58:18 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4E3E96B0070; Mon, 1 Feb 2021 13:58:18 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0191.hostedemail.com [216.40.44.191]) by kanga.kvack.org (Postfix) with ESMTP id 382FA6B006C for ; Mon, 1 Feb 2021 13:58:18 -0500 (EST) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id E7507181AEF1A for ; Mon, 1 Feb 2021 18:58:17 +0000 (UTC) X-FDA: 77770609434.24.dogs85_3c04b2b275c4 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin24.hostedemail.com (Postfix) with ESMTP id C9C301A4A0 for ; Mon, 1 Feb 2021 18:58:17 +0000 (UTC) X-HE-Tag: dogs85_3c04b2b275c4 X-Filterd-Recvd-Size: 3340 Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by imf05.hostedemail.com (Postfix) with ESMTP for ; Mon, 1 Feb 2021 18:58:15 +0000 (UTC) IronPort-SDR: 62qS//4MSRluMIKEcx1sM5UtSy8FpK1wOouHLWF4qFPKWHx2OhoQS8AzGjfR76nUxJQQmZhKc1 vMRjjks5ZvVQ== X-IronPort-AV: E=McAfee;i="6000,8403,9882"; a="168416071" X-IronPort-AV: E=Sophos;i="5.79,393,1602572400"; d="scan'208";a="168416071" Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Feb 2021 10:58:14 -0800 IronPort-SDR: mFCnqgrFuZMebcpZHoL5TJBZXYtUQmrYnBnXWFsNcJDi+zpaRIvoqXbnuPVNBNTAz0/krOjbvW K27HBSXRh24A== X-IronPort-AV: E=Sophos;i="5.79,393,1602572400"; d="scan'208";a="355881295" Received: from agluck-desk2.sc.intel.com (HELO agluck-desk2.amr.corp.intel.com) ([10.3.52.146]) by orsmga003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Feb 2021 10:58:13 -0800 Date: Mon, 1 Feb 2021 10:58:12 -0800 From: "Luck, Tony" To: Borislav Petkov Cc: x86@kernel.org, Andrew Morton , Peter Zijlstra , Darren Hart , Andy Lutomirski , linux-kernel@vger.kernel.org, linux-edac@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v5] x86/mce: Avoid infinite loop for copy from user recovery Message-ID: <20210201185812.GA54867@agluck-desk2.amr.corp.intel.com> References: <20210115205103.GA5920@agluck-desk2.amr.corp.intel.com> <20210115232346.GA7967@agluck-desk2.amr.corp.intel.com> <20210119105632.GF27433@zn.tnic> <20210119235759.GA9970@agluck-desk2.amr.corp.intel.com> <20210120121812.GF825@zn.tnic> <20210121210959.GA10304@agluck-desk2.amr.corp.intel.com> <20210125225509.GA7149@agluck-desk2.amr.corp.intel.com> <20210126110314.GC6514@zn.tnic> <20210126223605.GA14355@agluck-desk2.amr.corp.intel.com> <20210128175735.GB2120@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210128175735.GB2120@zn.tnic> X-Bogosity: Ham, tests=bogofilter, spamicity=0.004133, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jan 28, 2021 at 06:57:35PM +0100, Borislav Petkov wrote: > Crazy idea: if you still can reproduce on -rc3, you could bisect: i.e., > if you apply the patch on -rc3 and it explodes and if you apply the same > patch on -rc5 and it works, then that could be a start... Yeah, don't > have a better idea here. :-\ I tried reporoducing (applied the original patch I posted back to -rc3) and the same issue stubbornly refused to show up again. But I did hit something with the same signature (overflow bit set in bank 1) while running my futex test (which has two processes mapping the poison page). This time I *do* understand what happened. The test failed when the two processes were running on the two hyperhtreads of the same core. Seeing overflow in this case is understandable because bank 1 MSRs on my test machine are shared between the HT threads. When I run the test again using taskset(1) to only allowing running on thread 0 of each core, it keeps going for hunderds of iterations. I'm not sure I can stitch together how this overflow also happened for my single process test. Maybe a migration from one HT thread to the other at an awkward moment? -Tony