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,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 5A119C47097 for ; Fri, 4 Jun 2021 02:03:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3711460FE9 for ; Fri, 4 Jun 2021 02:03:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230033AbhFDCFA (ORCPT ); Thu, 3 Jun 2021 22:05:00 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:4466 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229576AbhFDCE6 (ORCPT ); Thu, 3 Jun 2021 22:04:58 -0400 Received: from dggemv704-chm.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Fx5ZJ2cJgzYqJ4; Fri, 4 Jun 2021 10:00:24 +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; Fri, 4 Jun 2021 10:03:09 +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; Fri, 4 Jun 2021 10:03:08 +0800 Subject: Re: [RFC] /dev/ioasid uAPI proposal To: Jacob Pan CC: Jason Gunthorpe , Lu Baolu , "Tian, Kevin" , LKML , Joerg Roedel , David Woodhouse , "iommu@lists.linux-foundation.org" , "kvm@vger.kernel.org" , "Alex Williamson (alex.williamson@redhat.com)" , Jason Wang , Eric Auger , Jonathan Corbet , "Raj, Ashok" , "Liu, Yi L" , "Wu, Hao" , "Jiang, Dave" , Jean-Philippe Brucker , David Gibson , Kirti Wankhede , Robin Murphy , Zenghui Yu , "wanghaibin.wang@huawei.com" References: <01fe5034-42c8-6923-32f1-e287cc36bccc@linux.intel.com> <20210601173323.GN1002214@nvidia.com> <23a482f9-b88a-da98-3800-f3fd9ea85fbd@huawei.com> <20210603111914.653c4f61@jacob-builder> From: Shenming Lu Message-ID: Date: Fri, 4 Jun 2021 10:03:08 +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: <20210603111914.653c4f61@jacob-builder> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.185.220] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) 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 2021/6/4 2:19, Jacob Pan wrote: > Hi Shenming, > > On Wed, 2 Jun 2021 12:50:26 +0800, Shenming Lu > wrote: > >> On 2021/6/2 1:33, Jason Gunthorpe wrote: >>> On Tue, Jun 01, 2021 at 08:30:35PM +0800, Lu Baolu wrote: >>> >>>> 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. >>> >>> I'm still confused why drivers need fault handlers at all? >> >> Essentially it is the userspace that needs the fault handlers, >> one case is to deliver the faults to the vIOMMU, and another >> case is to enable IOPF on the GPA address space for on-demand >> paging, it seems that both could be specified in/through the >> IOASID_ALLOC ioctl? >> > I would think IOASID_BIND_PGTABLE is where fault handler should be > registered. There wouldn't be any IO page fault without the binding anyway. Yeah, I also proposed this before, registering the handler in the BIND_PGTABLE ioctl does make sense for the guest page faults. :-) But how about the page faults from the GPA address space (it's page table is mapped through the MAP_DMA ioctl)? From your point of view, it seems that we should register the handler for the GPA address space in the (first) MAP_DMA ioctl. > > I also don't understand why device drivers should register the fault > handler, the fault is detected by the pIOMMU and injected to the vIOMMU. So > I think it should be the IOASID itself register the handler. Yeah, and it can also be said that the provider of the page table registers the handler (Baolu). Thanks, Shenming