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, URIBL_BLOCKED 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 49F5EC4320E for ; Mon, 30 Aug 2021 15:41:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 34E6860F44 for ; Mon, 30 Aug 2021 15:41:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237647AbhH3Pmm convert rfc822-to-8bit (ORCPT ); Mon, 30 Aug 2021 11:42:42 -0400 Received: from mga12.intel.com ([192.55.52.136]:48073 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237460AbhH3Pmk (ORCPT ); Mon, 30 Aug 2021 11:42:40 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10092"; a="197860326" X-IronPort-AV: E=Sophos;i="5.84,363,1620716400"; d="scan'208";a="197860326" Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Aug 2021 08:41:46 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.84,363,1620716400"; d="scan'208";a="427871610" Received: from fmsmsx603.amr.corp.intel.com ([10.18.126.83]) by orsmga003.jf.intel.com with ESMTP; 30 Aug 2021 08:41:46 -0700 Received: from fmsmsx611.amr.corp.intel.com (10.18.126.91) by fmsmsx603.amr.corp.intel.com (10.18.126.83) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2242.10; Mon, 30 Aug 2021 08:41:45 -0700 Received: from fmsmsx610.amr.corp.intel.com (10.18.126.90) by fmsmsx611.amr.corp.intel.com (10.18.126.91) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2242.10; Mon, 30 Aug 2021 08:41:45 -0700 Received: from fmsmsx610.amr.corp.intel.com ([10.18.126.90]) by fmsmsx610.amr.corp.intel.com ([10.18.126.90]) with mapi id 15.01.2242.010; Mon, 30 Aug 2021 08:41:45 -0700 From: "Luck, Tony" To: Matthew Wilcox CC: Al Viro , Thomas Gleixner , Linus Torvalds , Andreas Gruenbacher , Christoph Hellwig , "Darrick J. Wong" , Jan Kara , cluster-devel , linux-fsdevel , Linux Kernel Mailing List , "ocfs2-devel@oss.oracle.com" , Borislav Petkov , X86-ML Subject: RE: [PATCH v7 05/19] iov_iter: Introduce fault_in_iov_iter_writeable Thread-Topic: [PATCH v7 05/19] iov_iter: Introduce fault_in_iov_iter_writeable Thread-Index: AQHXm5pzAH4qSaa/BkWiD/swcmZu0auJ6p2AgAAE7YCAAAHvAP//xYSWgAJ7rdA= Date: Mon, 30 Aug 2021 15:41:45 +0000 Message-ID: <65cdd5f19431423dac13fbb13719ba55@intel.com> References: <20210827232246.GA1668365@agluck-desk2.amr.corp.intel.com> <87r1edgs2w.ffs@tglx> In-Reply-To: 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: 8BIT MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >> No #MC on stores. Just on loads. Note that you can't clear poison >> state with a series of small writes to the cache line. But a single >> 64-byte store might do it (architects didn't want to guarantee that >> it would work when I asked about avx512 stores to clear poison >> many years ago). > > Dave Jiang thinks MOVDIR64B clears poison. > > http://archive.lwn.net:8080/linux-kernel/157617505636.42350.1170110675242558018.stgit@djiang5-desk3.ch.intel.com/ MOVDIR64B has some explicit guarantees (does a write-back invalidate if the target is already in the cache) that a 64-byte avx512 write doesn't. Of course it would stop working if some future CPU were to have a longer than 64 bytes cache line. -Tony