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 7E102C433B4 for ; Tue, 20 Apr 2021 01:26:12 +0000 (UTC) Received: from smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E9695613AC for ; Tue, 20 Apr 2021 01:26:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E9695613AC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id A7D23605A2; Tue, 20 Apr 2021 01:26:11 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id flY8ZGVj4IYd; Tue, 20 Apr 2021 01:26:10 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [IPv6:2605:bc80:3010:104::8cd3:938]) by smtp3.osuosl.org (Postfix) with ESMTP id A3643607C2; Tue, 20 Apr 2021 01:26:10 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 5E351C000F; Tue, 20 Apr 2021 01:26:10 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [IPv6:2605:bc80:3010::137]) by lists.linuxfoundation.org (Postfix) with ESMTP id C9FB8C000B for ; Tue, 20 Apr 2021 01:26:08 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id B0E4340347 for ; Tue, 20 Apr 2021 01:26:08 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id zR7nM-lw2bly for ; Tue, 20 Apr 2021 01:26:03 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from szxga04-in.huawei.com (szxga04-in.huawei.com [45.249.212.190]) by smtp4.osuosl.org (Postfix) with ESMTPS id 5E79240355 for ; Tue, 20 Apr 2021 01:26:03 +0000 (UTC) Received: from DGGEMS412-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4FPQsw6RDnzmdXJ; Tue, 20 Apr 2021 09:23:00 +0800 (CST) Received: from [10.174.187.224] (10.174.187.224) by DGGEMS412-HUB.china.huawei.com (10.3.19.212) with Microsoft SMTP Server id 14.3.498.0; Tue, 20 Apr 2021 09:25:54 +0800 Subject: Re: [PATCH v3 02/12] iommu: Add iommu_split_block interface To: Lu Baolu , , , , Robin Murphy , Will Deacon , "Joerg Roedel" , Yi Sun , "Jean-Philippe Brucker" , Jonathan Cameron , Tian Kevin References: <20210413085457.25400-1-zhukeqian1@huawei.com> <20210413085457.25400-3-zhukeqian1@huawei.com> <491da550-dc54-42e6-ac91-13d411575fad@huawei.com> From: Keqian Zhu Message-ID: Date: Tue, 20 Apr 2021 09:25:53 +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: X-Originating-IP: [10.174.187.224] X-CFilter-Loop: Reflected Cc: jiangkunkun@huawei.com, Cornelia Huck , Kirti Wankhede , lushenming@huawei.com, Alex Williamson , wanghaibin.wang@huawei.com X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" Hi Baolu, On 2021/4/19 21:33, Lu Baolu wrote: > Hi Keqian, > > On 2021/4/19 17:32, Keqian Zhu wrote: >>>> +EXPORT_SYMBOL_GPL(iommu_split_block); >>> Do you really have any consumers of this interface other than the dirty >>> bit tracking? If not, I don't suggest to make this as a generic IOMMU >>> interface. >>> >>> There is an implicit requirement for such interfaces. The >>> iommu_map/unmap(iova, size) shouldn't be called at the same time. >>> Currently there's no such sanity check in the iommu core. A poorly >>> written driver could mess up the kernel by misusing this interface. >> Yes, I don't think up a scenario except dirty tracking. >> >> Indeed, we'd better not make them as a generic interface. >> >> Do you have any suggestion that underlying iommu drivers can share these code but >> not make it as a generic iommu interface? >> >> I have a not so good idea. Make the "split" interfaces as a static function, and >> transfer the function pointer to start_dirty_log. But it looks weird and inflexible. > > I understand splitting/merging super pages is an optimization, but not a > functional requirement. So is it possible to let the vendor iommu driver > decide whether splitting super pages when starting dirty bit tracking > and the opposite operation during when stopping it? The requirement for Right. If I understand you correct, actually that is what this series does. We realized split/merge in IOMMU core layer, but don't force vendor driver to use it. The problem is that when we expose these interfaces to vendor IOMMU driver, will also expose them to upper driver. > upper layer is that starting/stopping dirty bit tracking and > mapping/unmapping are mutually exclusive. OK, I will explicitly add the hints. Thanks. Thanks, Keqian > >> >> On the other hand, if a driver calls map/unmap with split/merge at the same time, >> it's a bug of driver, it should follow the rule. >> > > Best regards, > baolu > . > _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu