From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1753921AbdLHNsR (ORCPT <rfc822;w@1wt.eu>);
        Fri, 8 Dec 2017 08:48:17 -0500
Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:38898 "EHLO
        foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1753331AbdLHNsQ (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 8 Dec 2017 08:48:16 -0500
Subject: Re: [PATCH v3 15/16] iommu: introduce page response function
To: Alex Williamson <alex.williamson@redhat.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>,
        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>, Joerg Roedel <joro@8bytes.org>,
        David Woodhouse <dwmw2@infradead.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Rafael Wysocki <rafael.j.wysocki@intel.com>,
        Lan Tianyu <tianyu.lan@intel.com>, Jean Delvare <khali@linux-fr.org>,
        Will Deacon <Will.Deacon@arm.com>,
        "Kumar, Sanjay K" <sanjay.k.kumar@intel.com>
References: <1510944914-54430-1-git-send-email-jacob.jun.pan@linux.intel.com>
 <1510944914-54430-16-git-send-email-jacob.jun.pan@linux.intel.com>
 <93661c1c-2d3b-295f-0b9d-52e50ea9e1d0@arm.com>
 <20171204133715.50c45136@jacob-builder>
 <a6cfc27a-6121-1e67-6e0d-f94a383bcd6f@arm.com>
 <20171206112521.1edf8e9b@jacob-builder>
 <39fcbbd2-2e6a-f05a-8cb4-8e3ad4ead369@arm.com>
 <20171207145641.50830562@t450s.home>
From: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Message-ID: <af3c1d0f-e325-9507-0d59-7faadc79d66b@arm.com>
Date: Fri, 8 Dec 2017 13:51:48 +0000
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.4.0
MIME-Version: 1.0
In-Reply-To: <20171207145641.50830562@t450s.home>
Content-Type: text/plain; charset=windows-1252
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 07/12/17 21:56, Alex Williamson wrote:
[...]
>> Seems like VFIO should enforce this quota, since the IOMMU layer doesn't
>> know which device is assigned to which VM. If it's the IOMMU that enforces
>> quotas per device and a VM has 15 devices assigned, then the guest can
>> still DoS the IOMMU.
> 
> VFIO also doesn't know about VMs.  We know that devices attached to the
> same container are probably used by the same user, but once we add
> viommu, each device(group) uses its own container and we have no idea
> they're associated.  So, no to VM based accounting, and it seems like
> an IOMMU problem, X number of outstanding requests per device.  Thanks,

Ok. It's not clear anyway how the architecture and implementations expect
us to virtualize stall, I'll try to clarify it.

Thanks,
Jean