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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 753D8C49EA4 for ; Tue, 22 Jun 2021 17:46:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 60E3A6109E for ; Tue, 22 Jun 2021 17:46:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232465AbhFVRsw (ORCPT ); Tue, 22 Jun 2021 13:48:52 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:3301 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232454AbhFVRsi (ORCPT ); Tue, 22 Jun 2021 13:48:38 -0400 Received: from fraeml701-chm.china.huawei.com (unknown [172.18.147.201]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4G8YTv621Sz6H7Gp; Wed, 23 Jun 2021 01:36:19 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml701-chm.china.huawei.com (10.206.15.50) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Tue, 22 Jun 2021 19:46:19 +0200 Received: from [10.47.89.126] (10.47.89.126) 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; Tue, 22 Jun 2021 18:46:18 +0100 Subject: Re: [PATCH 0/6] iommu: Enable devices to request non-strict DMA, starting with QCom SD/MMC To: Douglas Anderson , , , , , , , , , , CC: , , , , , , , , , , , , Andy Gross , Bartosz Golaszewski , Dan Williams , "Geert Uytterhoeven" , Heikki Krogerus , Randy Dunlap , References: <20210621235248.2521620-1-dianders@chromium.org> From: John Garry Message-ID: Date: Tue, 22 Jun 2021 18:39:50 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.1.2 MIME-Version: 1.0 In-Reply-To: <20210621235248.2521620-1-dianders@chromium.org> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.47.89.126] X-ClientProxiedBy: lhreml721-chm.china.huawei.com (10.201.108.72) 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 22/06/2021 00:52, Douglas Anderson wrote: > > This patch attempts to put forward a proposal for enabling non-strict > DMA on a device-by-device basis. The patch series requests non-strict > DMA for the Qualcomm SDHCI controller as a first device to enable, > getting a nice bump in performance with what's believed to be a very > small drop in security / safety (see the patch for the full argument). > > As part of this patch series I am end up slightly cleaning up some of > the interactions between the PCI subsystem and the IOMMU subsystem but > I don't go all the way to fully remove all the tentacles. Specifically > this patch series only concerns itself with a single aspect: strict > vs. non-strict mode for the IOMMU. I'm hoping that this will be easier > to talk about / reason about for more subsystems compared to overall > deciding what it means for a device to be "external" or "untrusted". > > If something like this patch series ends up being landable, it will > undoubtedly need coordination between many maintainers to land. I > believe it's fully bisectable but later patches in the series > definitely depend on earlier ones. Sorry for the long CC list. :( > JFYI, In case to missed it, and I know it's not the same thing as you want, above, but the following series will allow you to build the kernel to default to lazy mode: https://lore.kernel.org/linux-iommu/1624016058-189713-1-git-send-email-john.garry@huawei.com/T/#m21bc07b9353b3ba85f2a40557645c2bcc13cbb3e So iommu.strict=0 would be no longer always required for arm64. Thanks, John > > Douglas Anderson (6): > drivers: base: Add the concept of "pre_probe" to drivers > drivers: base: Add bits to struct device to control iommu strictness > PCI: Indicate that we want to force strict DMA for untrusted devices > iommu: Combine device strictness requests with the global default > iommu: Stop reaching into PCIe devices to decide strict vs. non-strict > mmc: sdhci-msm: Request non-strict IOMMU mode > > drivers/base/dd.c | 10 +++++-- > drivers/iommu/dma-iommu.c | 2 +- > drivers/iommu/iommu.c | 56 +++++++++++++++++++++++++++-------- > drivers/mmc/host/sdhci-msm.c | 8 +++++ > drivers/pci/probe.c | 4 ++- > include/linux/device.h | 11 +++++++ > include/linux/device/driver.h | 9 ++++++ > include/linux/iommu.h | 2 ++ > 8 files changed, 85 insertions(+), 17 deletions(-) >