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=-5.3 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 0E9CBC433DB for ; Fri, 29 Jan 2021 06:14:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD96964DFB for ; Fri, 29 Jan 2021 06:14:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232081AbhA2GNq (ORCPT ); Fri, 29 Jan 2021 01:13:46 -0500 Received: from szxga06-in.huawei.com ([45.249.212.32]:11907 "EHLO szxga06-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232076AbhA2GNn (ORCPT ); Fri, 29 Jan 2021 01:13:43 -0500 Received: from DGGEMS410-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga06-in.huawei.com (SkyGuard) with ESMTP id 4DRn6g44f9zjDnm; Fri, 29 Jan 2021 14:11:55 +0800 (CST) Received: from [10.174.184.42] (10.174.184.42) by DGGEMS410-HUB.china.huawei.com (10.3.19.210) with Microsoft SMTP Server id 14.3.498.0; Fri, 29 Jan 2021 14:12:47 +0800 Subject: Re: [PATCH 1/1] iommu/arm-smmu-v3: add support for BBML To: Robin Murphy , Will Deacon 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> <301590f1-817b-d8eb-1585-31208cba18af@arm.com> CC: Jean-Philippe Brucker , linux-kernel , iommu , Yang Yingliang , linux-arm-kernel From: Keqian Zhu Message-ID: <29fd5c20-faeb-1fd3-6535-4fca60463d01@huawei.com> Date: Fri, 29 Jan 2021 14:12:46 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: <301590f1-817b-d8eb-1585-31208cba18af@arm.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.184.42] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/1/29 0:17, Robin Murphy wrote: > 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"). OK, I Get it. Thanks. Keqian. > > 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 >>>> >>> . >>> > . >