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=-10.4 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 0DD8AC4338F for ; Fri, 30 Jul 2021 09:24:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E503161054 for ; Fri, 30 Jul 2021 09:24:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238129AbhG3JYv (ORCPT ); Fri, 30 Jul 2021 05:24:51 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:3537 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230359AbhG3JYu (ORCPT ); Fri, 30 Jul 2021 05:24:50 -0400 Received: from fraeml710-chm.china.huawei.com (unknown [172.18.147.226]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4GbhZN6Bmyz6G9MK; Fri, 30 Jul 2021 17:15:24 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml710-chm.china.huawei.com (10.206.15.59) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Fri, 30 Jul 2021 11:24:44 +0200 Received: from [10.47.25.95] (10.47.25.95) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Fri, 30 Jul 2021 10:24:43 +0100 Subject: Re: [PATCH v2 22/24] iommu: Allow enabling non-strict mode dynamically To: Robin Murphy , , CC: , , , , , References: From: John Garry Message-ID: <985c0a86-21d9-8d4b-0c33-c00b94e41bb9@huawei.com> Date: Fri, 30 Jul 2021 10:24:24 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.47.25.95] X-ClientProxiedBy: lhreml735-chm.china.huawei.com (10.201.108.86) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28/07/2021 16:58, Robin Murphy wrote: > Allocating and enabling a flush queue is in fact something we can > reasonably do while a DMA domain is active, without having to rebuild it > from scratch. Thus we can allow a strict -> non-strict transition from > sysfs without requiring to unbind the device's driver, which is of > particular interest to users who want to make selective relaxations to > critical devices like the one serving their root filesystem. > > Disabling and draining a queue also seems technically possible to > achieve without rebuilding the whole domain, but would certainly be more > involved. Furthermore there's not such a clear use-case for tightening > up security*after* the device may already have done whatever it is that > you don't trust it not to do, so we only consider the relaxation case. > > Signed-off-by: Robin Murphy Reviewed-by: John Garry