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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, 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 3F33EC352BE for ; Fri, 17 Apr 2020 07:47:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 150802137B for ; Fri, 17 Apr 2020 07:47:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="GC9feK7P" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729301AbgDQHrL (ORCPT ); Fri, 17 Apr 2020 03:47:11 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:39592 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729201AbgDQHrJ (ORCPT ); Fri, 17 Apr 2020 03:47:09 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1587109627; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=OnCFlVZKT1kcPJl0tm16QfqztTjiCxEfefQVkmAO2Q4=; b=GC9feK7PtzBwUH+6Nhep+txosiOfxZQdmcXF/fJdjPOOcsUj51Vlg2lBQQ+bAznzF8dW23 0B2SbK1TZonHR1XYS/kfuB0feZnINUvHN6OpOKTHd+D0YqABlJZMo7lufYiv9fI8RJmBpn u/eftDwvEOnA5W6qX1hUqs+ob/bVCaA= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-301--znvfP_QP-a_NK8x7vIE7A-1; Fri, 17 Apr 2020 03:47:03 -0400 X-MC-Unique: -znvfP_QP-a_NK8x7vIE7A-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 116C118B9FC8; Fri, 17 Apr 2020 07:47:02 +0000 (UTC) Received: from [10.36.115.53] (ovpn-115-53.ams2.redhat.com [10.36.115.53]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E56D9129F81; Fri, 17 Apr 2020 07:46:56 +0000 (UTC) Subject: Re: [PATCH v11 05/10] iommu/vt-d: Add bind guest PASID support To: "Tian, Kevin" , Jacob Pan Cc: Yi L , Alex Williamson , "Raj, Ashok" , David Woodhouse , LKML , "iommu@lists.linux-foundation.org" , Jean-Philippe Brucker , Jonathan Cameron References: <1585939334-21396-1-git-send-email-jacob.jun.pan@linux.intel.com> <1585939334-21396-6-git-send-email-jacob.jun.pan@linux.intel.com> <20200410124557.4012b99b@jacob-builder> <6d9721a8-2198-5ecd-6c8b-fc43ff2ad7e1@redhat.com> From: Auger Eric Message-ID: <2025736d-e7f2-d746-e030-e609b2f465e2@redhat.com> Date: Fri, 17 Apr 2020 09:46:55 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Kevin, On 4/17/20 4:45 AM, Tian, Kevin wrote: >> From: Auger Eric >> Sent: Thursday, April 16, 2020 6:43 PM >> > [...] >>>>> + if (svm) { >>>>> + /* >>>>> + * If we found svm for the PASID, there must be at >>>>> + * least one device bond, otherwise svm should be >>>>> freed. >>>>> + */ >>>>> + if (WARN_ON(list_empty(&svm->devs))) { >>>>> + ret = -EINVAL; >>>>> + goto out; >>>>> + } >>>>> + >>>>> + for_each_svm_dev(sdev, svm, dev) { >>>>> + /* In case of multiple sub-devices of the >>>>> same pdev >>>>> + * assigned, we should allow multiple bind >>>>> calls with >>>>> + * the same PASID and pdev. >>>>> + */ >>>>> + sdev->users++; >>>> What if this is not an mdev device. Is it also allowed? >>> Yes. IOMMU and VT-d driver is not mdev aware. Here mdev is just an >>> example of normal use case. You can bind the same PCI device (PF or >>> SRIOV VF) more than once to the same PASID. Just need to unbind also. >> >> I don't get the point of binding a non mdev device several times with >> the same PASID. Do you intend to allow that at userspace level or >> prevent this from happening in VFIO? > > I feel it's better to prevent this from happening, otherwise VFIO also > needs to track the bind count and do multiple unbinds at mm_exit. > But it's not necessary to prevent it in VFIO. We can check here > upon whether aux_domain is valid, and if not return -EBUSY. Ah OK. So if we can detect the case here it is even better Thanks Eric > >> >> Besides, the comment is a bit misleading as it gives the impression it >> is only true for mdev and there is no associated check. > > Thanks > Kevin >