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 E2B9DC433DB for ; Fri, 8 Jan 2021 23:09:04 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 670E623AA7 for ; Fri, 8 Jan 2021 23:09:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 670E623AA7 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 809368D01BB; Fri, 8 Jan 2021 18:09:03 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 7B8BB8D01B7; Fri, 8 Jan 2021 18:09:03 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6CF6A8D01BB; Fri, 8 Jan 2021 18:09:03 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0091.hostedemail.com [216.40.44.91]) by kanga.kvack.org (Postfix) with ESMTP id 59F6C8D01B7 for ; Fri, 8 Jan 2021 18:09:03 -0500 (EST) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 27E91824556B for ; Fri, 8 Jan 2021 23:09:03 +0000 (UTC) X-FDA: 77684150166.25.laugh96_030f900274f6 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin25.hostedemail.com (Postfix) with ESMTP id 064561804E3A1 for ; Fri, 8 Jan 2021 23:09:02 +0000 (UTC) X-HE-Tag: laugh96_030f900274f6 X-Filterd-Recvd-Size: 3583 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by imf50.hostedemail.com (Postfix) with ESMTP for ; Fri, 8 Jan 2021 23:09:00 +0000 (UTC) IronPort-SDR: eVNJymfysFu9eSJJRFok+rDcaO/cSIF0Z7MRAM6Hz6051/4tuZpEBuMS1dP9aT2SKyB2Fmu22N KctosDUM+IQQ== X-IronPort-AV: E=McAfee;i="6000,8403,9858"; a="175088626" X-IronPort-AV: E=Sophos;i="5.79,333,1602572400"; d="scan'208";a="175088626" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Jan 2021 15:08:59 -0800 IronPort-SDR: +ofVZIE9INDn8Rs02famlryxSS4bKsPILtr6un1eWfK1B2Zc3b2OGsDZ7fD8E6NxUSpLZ/XztJ TgONT3kizRvQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.79,333,1602572400"; d="scan'208";a="568217572" Received: from fmsmsx605.amr.corp.intel.com ([10.18.126.85]) by fmsmga006.fm.intel.com with ESMTP; 08 Jan 2021 15:08:59 -0800 Received: from fmsmsx610.amr.corp.intel.com (10.18.126.90) by fmsmsx605.amr.corp.intel.com (10.18.126.85) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Fri, 8 Jan 2021 15:08:59 -0800 Received: from fmsmsx610.amr.corp.intel.com (10.18.126.90) by fmsmsx610.amr.corp.intel.com (10.18.126.90) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Fri, 8 Jan 2021 15:08:58 -0800 Received: from fmsmsx610.amr.corp.intel.com ([10.18.126.90]) by fmsmsx610.amr.corp.intel.com ([10.18.126.90]) with mapi id 15.01.1713.004; Fri, 8 Jan 2021 15:08:58 -0800 From: "Luck, Tony" To: Peter Zijlstra CC: Borislav Petkov , "x86@kernel.org" , "Andrew Morton" , Darren Hart , Andy Lutomirski , "linux-kernel@vger.kernel.org" , "linux-edac@vger.kernel.org" , "linux-mm@kvack.org" Subject: RE: [PATCH 2/2] futex, x86/mce: Avoid double machine checks Thread-Topic: [PATCH 2/2] futex, x86/mce: Avoid double machine checks Thread-Index: AQHW5gzS994+pBz0+EqmRhsWwoX/Iaoe2m6A//9/AZA= Date: Fri, 8 Jan 2021 23:08:58 +0000 Message-ID: <4493a015ffcd4d82bbea7d1e5c2e73e4@intel.com> References: <20210108222251.14391-1-tony.luck@intel.com> <20210108222251.14391-3-tony.luck@intel.com> <20210108224715.GB2453@worktop.programming.kicks-ass.net> In-Reply-To: <20210108224715.GB2453@worktop.programming.kicks-ass.net> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: dlp-product: dlpe-windows dlp-reaction: no-action dlp-version: 11.5.1.3 x-originating-ip: [10.1.200.100] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.008446, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > I think this is horrid; why can't we have it return something different > then -EFAULT instead? I did consider this ... but it appears that architectures aren't unified in= the return value from get_user() Here's another function involved in the futex call chain leading to this: static int get_futex_value_locked(u32 *dest, u32 __user *from) { int ret; pagefault_disable(); ret =3D __get_user(*dest, from); pagefault_enable(); return ret ? -EFAULT : 0; } It seems like the expectation here is just "zero or not" and we don't care what the "not" value is ... just turn it into -EFAULT. -Tony