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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 A820FC433DB for ; Thu, 28 Jan 2021 16:18:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 684ED64DE5 for ; Thu, 28 Jan 2021 16:18:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232492AbhA1QS1 (ORCPT ); Thu, 28 Jan 2021 11:18:27 -0500 Received: from foss.arm.com ([217.140.110.172]:35152 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232091AbhA1QSY (ORCPT ); Thu, 28 Jan 2021 11:18:24 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 548D513D5; Thu, 28 Jan 2021 08:17:37 -0800 (PST) Received: from [10.57.35.163] (unknown [10.57.35.163]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 37ACE3F7C3; Thu, 28 Jan 2021 08:17:36 -0800 (PST) Subject: Re: [PATCH 1/1] iommu/arm-smmu-v3: add support for BBML To: Keqian Zhu , Will Deacon Cc: Jean-Philippe Brucker , linux-kernel , iommu , Yang Yingliang , linux-arm-kernel References: <20201126034230.777-1-thunder.leizhen@huawei.com> <20210122125132.GB24102@willie-the-truck> <1bfd1ca0-953e-e943-f87e-144d5537bd0c@arm.com> <20210126101230.GA29204@willie-the-truck> <8a9685ec-67aa-824f-5429-f408bf79c5ab@huawei.com> <32f4752f-6954-183a-a0c1-b5d719c85b67@huawei.com> <319e3532-4555-7431-9d6f-3c3b7c11a5d9@arm.com> From: Robin Murphy Message-ID: <301590f1-817b-d8eb-1585-31208cba18af@arm.com> Date: Thu, 28 Jan 2021 16:17:35 +0000 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021-01-28 15:18, Keqian Zhu wrote: > > > On 2021/1/27 17:39, Robin Murphy wrote: >> On 2021-01-27 07:36, Keqian Zhu wrote: >>> >>> >>> On 2021/1/27 10:01, Leizhen (ThunderTown) wrote: >>>> >>>> >>>> On 2021/1/26 18:12, Will Deacon wrote: >>>>> On Mon, Jan 25, 2021 at 08:23:40PM +0000, Robin Murphy wrote: >>>>>> Now we probably will need some degreee of BBML feature awareness for the >>>>>> sake of SVA if and when we start using it for CPU pagetables, but I still >>>>>> cannot see any need to consider it in io-pgtable. >>>>> >>>>> Agreed; I don't think this is something that io-pgtable should have to care >>>>> about. >>> Hi, >>> >>> I have a question here :-). >>> If the old table is not live, then the break procedure seems unnecessary. Do I miss something? >> >> The MMU is allowed to prefetch translations at any time, so not following the proper update procedure could still potentially lead to a TLB conflict, even if there's no device traffic to worry about disrupting. >> >> Robin. > > Thanks. Does the MMU you mention here includes MMU and SMMU? I know that at SMMU side, ATS can prefetch translation. Yes, both - VMSAv8 allows speculative translation table walks, so SMMUv3 inherits from there (per 3.21.1 "Translation tables and TLB invalidation completion behavior"). Robin. > > Keqian >> >>> Thanks, >>> Keqian >>> >>>> >>>> Yes, the SVA works in stall mode, and the failed device access requests are not >>>> discarded. >>>> >>>> Let me look for examples. The BBML usage scenario was told by a former colleague. >>>> >>>>> >>>>> Will >>>>> >>>>> . >>>>> >>>> >>>> >>>> _______________________________________________ >>>> linux-arm-kernel mailing list >>>> linux-arm-kernel@lists.infradead.org >>>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >>>> . >>>> >>> _______________________________________________ >>> iommu mailing list >>> iommu@lists.linux-foundation.org >>> https://lists.linuxfoundation.org/mailman/listinfo/iommu >>> >> . >>