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=-5.9 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 5A2FCC47092 for ; Tue, 1 Jun 2021 13:11:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 340AD613BD for ; Tue, 1 Jun 2021 13:11:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233921AbhFANMl (ORCPT ); Tue, 1 Jun 2021 09:12:41 -0400 Received: from szxga03-in.huawei.com ([45.249.212.189]:3367 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233768AbhFANMj (ORCPT ); Tue, 1 Jun 2021 09:12:39 -0400 Received: from dggemv704-chm.china.huawei.com (unknown [172.30.72.53]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4FvXW34ZMTz67Pr; Tue, 1 Jun 2021 21:07:11 +0800 (CST) Received: from dggpemm500022.china.huawei.com (7.185.36.162) by dggemv704-chm.china.huawei.com (10.3.19.47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Tue, 1 Jun 2021 21:10:55 +0800 Received: from [10.174.185.220] (10.174.185.220) by dggpemm500022.china.huawei.com (7.185.36.162) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Tue, 1 Jun 2021 21:10:54 +0800 Subject: Re: [RFC] /dev/ioasid uAPI proposal To: Lu Baolu , "Tian, Kevin" , LKML , Joerg Roedel , "Jason Gunthorpe" , David Woodhouse , "iommu@lists.linux-foundation.org" , "kvm@vger.kernel.org" , "Alex Williamson (alex.williamson@redhat.com)" , Jason Wang , Jean-Philippe Brucker CC: Eric Auger , Jonathan Corbet , "Raj, Ashok" , "Liu, Yi L" , "Wu, Hao" , "Jiang, Dave" , Jacob Pan , David Gibson , Kirti Wankhede , Robin Murphy , Zenghui Yu , "wanghaibin.wang@huawei.com" References: <01fe5034-42c8-6923-32f1-e287cc36bccc@linux.intel.com> From: Shenming Lu Message-ID: Date: Tue, 1 Jun 2021 21:10:42 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.2.2 MIME-Version: 1.0 In-Reply-To: <01fe5034-42c8-6923-32f1-e287cc36bccc@linux.intel.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.185.220] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500022.china.huawei.com (7.185.36.162) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/6/1 20:30, Lu Baolu wrote: > On 2021/6/1 15:15, Shenming Lu wrote: >> On 2021/6/1 13:10, Lu Baolu wrote: >>> Hi Shenming, >>> >>> On 6/1/21 12:31 PM, Shenming Lu wrote: >>>> On 2021/5/27 15:58, Tian, Kevin wrote: >>>>> /dev/ioasid provides an unified interface for managing I/O page tables for >>>>> devices assigned to userspace. Device passthrough frameworks (VFIO, vDPA, >>>>> etc.) are expected to use this interface instead of creating their own logic to >>>>> isolate untrusted device DMAs initiated by userspace. >>>>> >>>>> This proposal describes the uAPI of /dev/ioasid and also sample sequences >>>>> with VFIO as example in typical usages. The driver-facing kernel API provided >>>>> by the iommu layer is still TBD, which can be discussed after consensus is >>>>> made on this uAPI. >>>>> >>>>> It's based on a lengthy discussion starting from here: >>>>>      https://lore.kernel.org/linux-iommu/20210330132830.GO2356281@nvidia.com/ >>>>> >>>>> It ends up to be a long writing due to many things to be summarized and >>>>> non-trivial effort required to connect them into a complete proposal. >>>>> Hope it provides a clean base to converge. >>>>> >>>> [..] >>>> >>>>> /* >>>>>     * Page fault report and response >>>>>     * >>>>>     * This is TBD. Can be added after other parts are cleared up. Likely it >>>>>     * will be a ring buffer shared between user/kernel, an eventfd to notify >>>>>     * the user and an ioctl to complete the fault. >>>>>     * >>>>>     * The fault data is per I/O address space, i.e.: IOASID + faulting_addr >>>>>     */ >>>> Hi, >>>> >>>> It seems that the ioasid has different usage in different situation, it could >>>> be directly used in the physical routing, or just a virtual handle that indicates >>>> a page table or a vPASID table (such as the GPA address space, in the simple >>>> passthrough case, the DMA input to IOMMU will just contain a Stream ID, no >>>> Substream ID), right? >>>> >>>> And Baolu suggested that since one device might consume multiple page tables, >>>> it's more reasonable to have one fault handler per page table. By this, do we >>>> have to maintain such an ioasid info list in the IOMMU layer? >>> As discussed earlier, the I/O page fault and cache invalidation paths >>> will have "device labels" so that the information could be easily >>> translated and routed. >>> >>> So it's likely the per-device fault handler registering API in iommu >>> core can be kept, but /dev/ioasid will be grown with a layer to >>> translate and propagate I/O page fault information to the right >>> consumers. >> Yeah, having a general preprocessing of the faults in IOASID seems to be >> a doable direction. But since there may be more than one consumer at the >> same time, who is responsible for registering the per-device fault handler? > > The drivers register per page table fault handlers to /dev/ioasid which > will then register itself to iommu core to listen and route the per- > device I/O page faults. This is just a top level thought. Haven't gone > through the details yet. Need to wait and see what /dev/ioasid finally > looks like. OK. And it needs to be confirmed by Jean since we might migrate the code from io-pgfault.c to IOASID... Anyway, finalize /dev/ioasid first. Thanks, Shenming > > Best regards, > baolu > .