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,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 A5DF4C433ED for ; Tue, 11 May 2021 03:13:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 70F6D61584 for ; Tue, 11 May 2021 03:13:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229920AbhEKDOP (ORCPT ); Mon, 10 May 2021 23:14:15 -0400 Received: from mga07.intel.com ([134.134.136.100]:26066 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229465AbhEKDOH (ORCPT ); Mon, 10 May 2021 23:14:07 -0400 IronPort-SDR: KkcvMG3ElJBVcXePNnIfJLlIiB3QmYdqp6Uysg1y7FTtFHOz5e6kNNsnHDKbgLEj6mO7XF9EN6 Q0yOgf3A6kTw== X-IronPort-AV: E=McAfee;i="6200,9189,9980"; a="263273556" X-IronPort-AV: E=Sophos;i="5.82,290,1613462400"; d="scan'208";a="263273556" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 May 2021 20:12:58 -0700 IronPort-SDR: stKccw6CyTiwgY6Z4oynDLYVZ9iolDqy5GJI2whakNs9xp75faAiZ3QlNCdDdLhdiWlAPMdVj9 pZkA/PEv8pfQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.82,290,1613462400"; d="scan'208";a="621641217" Received: from allen-box.sh.intel.com (HELO [10.239.159.128]) ([10.239.159.128]) by fmsmga006.fm.intel.com with ESMTP; 10 May 2021 20:12:52 -0700 Cc: baolu.lu@linux.intel.com, Alex Williamson , Kirti Wankhede , Cornelia Huck , Jonathan Cameron , wanghaibin.wang@huawei.com, jiangkunkun@huawei.com, yuzenghui@huawei.com, lushenming@huawei.com Subject: Re: [RFC PATCH v4 01/13] iommu: Introduce dirty log tracking framework To: Keqian Zhu , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, iommu@lists.linux-foundation.org, Robin Murphy , Will Deacon , Joerg Roedel , Jean-Philippe Brucker , Yi Sun , Tian Kevin References: <20210507102211.8836-1-zhukeqian1@huawei.com> <20210507102211.8836-2-zhukeqian1@huawei.com> <18ac787a-179e-71f7-728b-c43feda80a16@huawei.com> <55fda826-9ab6-a3a0-b17e-a4d4879f00bc@linux.intel.com> From: Lu Baolu Message-ID: Date: Tue, 11 May 2021 11:12:07 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Keqian, On 5/10/21 7:07 PM, Keqian Zhu wrote: >>>> I suppose this interface is to ask the vendor IOMMU driver to check >>>> whether each device/iommu in the domain supports dirty bit tracking. >>>> But what will happen if new devices with different tracking capability >>>> are added afterward? >>> Yep, this is considered in the vfio part. We will query again after attaching or >>> detaching devices from the domain. When the domain becomes capable, we enable >>> dirty log for it. When it becomes not capable, we disable dirty log for it. >> If that's the case, why not putting this logic in the iommu subsystem so >> that it doesn't need to be duplicate in different upper layers? >> >> For example, add something like dirty_page_trackable in the struct of >> iommu_domain and ask the vendor iommu driver to update it once any >> device is added/removed to/from the domain. It's also better to disallow > If we do it, the upper layer still needs to query the capability from domain and switch > dirty log tracking for it. Or do you mean the domain can switch dirty log tracking automatically > when its capability change? If so, I think we're lack of some flexibility. The upper layer > may have it's own policy, such as only enable dirty log tracking when all domains are capable, > and disable dirty log tracking when just one domain is not capable. I may not get you. Assume that dirty_page_trackable is an attribution of an iommu_domain. This attribution might be changed once a new device (with different capability) added or removed. So it should be updated every time a new device is attached or detached. This work could be done by the vendor iommu driver on the path of dev_attach/dev_detach callback. For upper layers, before starting page tracking, they check the dirty_page_trackable attribution of the domain and start it only it's capable. Once the page tracking is switched on the vendor iommu driver (or iommu core) should block further device attach/detach operations until page tracking is stopped. > >> any domain attach/detach once the dirty page tracking is on. > Yep, this can greatly simplify our code logic, but I don't know whether our maintainers > agree that, as they may think that IOMMU dirty logging should not change original domain > behaviors. The maintainer owns the last word, but we need to work out a generic and self-contained API set. Best regards, baolu