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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 EEC0BC4321E for ; Fri, 7 Sep 2018 01:58:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7D61920857 for ; Fri, 7 Sep 2018 01:58:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7D61920857 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728849AbeIGGhM (ORCPT ); Fri, 7 Sep 2018 02:37:12 -0400 Received: from mga03.intel.com ([134.134.136.65]:56400 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726005AbeIGGhM (ORCPT ); Fri, 7 Sep 2018 02:37:12 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 06 Sep 2018 18:58:47 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,340,1531810800"; d="scan'208";a="69014501" Received: from allen-box.sh.intel.com (HELO [10.239.161.122]) ([10.239.161.122]) by fmsmga008.fm.intel.com with ESMTP; 06 Sep 2018 18:58:43 -0700 Cc: baolu.lu@linux.intel.com, "Tian, Kevin" , Joerg Roedel , David Woodhouse , "Raj, Ashok" , "Kumar, Sanjay K" , "Liu, Yi L" , "Sun, Yi Y" , "peterx@redhat.com" , Jean-Philippe Brucker , "iommu@lists.linux-foundation.org" , "linux-kernel@vger.kernel.org" , Jacob Pan Subject: Re: [PATCH v2 02/12] iommu/vt-d: Manage scalalble mode PASID tables To: Jacob Pan References: <20180830013524.28743-1-baolu.lu@linux.intel.com> <20180830013524.28743-3-baolu.lu@linux.intel.com> <44298d5c-5720-a382-07d1-a90a072ff24b@linux.intel.com> <20180906164317.786bbdda@jacob-builder> From: Lu Baolu Message-ID: <7e5faa39-376e-2c77-3891-9aac9092524a@linux.intel.com> Date: Fri, 7 Sep 2018 09:57:38 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180906164317.786bbdda@jacob-builder> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 09/07/2018 07:43 AM, Jacob Pan wrote: > On Thu, 6 Sep 2018 10:46:03 +0800 > Lu Baolu wrote: > >>>> @@ -224,7 +271,14 @@ struct pasid_entry >>>> *intel_pasid_get_entry(struct device *dev, int pasid) >>>> */ >>>> static inline void pasid_clear_entry(struct pasid_entry *pe) >>>> { >>>> - WRITE_ONCE(pe->val, 0); >>>> + WRITE_ONCE(pe->val[0], 0); >>>> + WRITE_ONCE(pe->val[1], 0); >>>> + WRITE_ONCE(pe->val[2], 0); >>>> + WRITE_ONCE(pe->val[3], 0); >>>> + WRITE_ONCE(pe->val[4], 0); >>>> + WRITE_ONCE(pe->val[5], 0); >>>> + WRITE_ONCE(pe->val[6], 0); >>>> + WRITE_ONCE(pe->val[7], 0); >>> >>> memset? >> >> The order is important here. Otherwise, the PRESENT bit of this pasid >> entry might still set while other fields contains invalid values. > > WRITE_ONCE/READ_ONCE will switch to __builtin_memcpy() in if the size > exceeds word size, ie. 64bit in this case. I don;t think compiler will > reorder built-in function. Beside, we only need to clear present and > FDP bit, right? Clear present and FDP bit is enough for hardare. But from software point of view, it's better to clear all bits with 0. Best regards, Lu Baolu