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=-5.6 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,URIBL_RED,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 C5596C07E95 for ; Tue, 13 Jul 2021 18:07:17 +0000 (UTC) Received: from smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 74BAE61374 for ; Tue, 13 Jul 2021 18:07:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 74BAE61374 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id 2B279608C7; Tue, 13 Jul 2021 18:07:17 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 4aUkL636e6uM; Tue, 13 Jul 2021 18:07:16 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp3.osuosl.org (Postfix) with ESMTPS id 33CB86059B; Tue, 13 Jul 2021 18:07:16 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 09820C0010; Tue, 13 Jul 2021 18:07:16 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by lists.linuxfoundation.org (Postfix) with ESMTP id 4D435C000E for ; Tue, 13 Jul 2021 18:07:13 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id 3915C40634 for ; Tue, 13 Jul 2021 18:07:13 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id JgOvs3BxGfIz for ; Tue, 13 Jul 2021 18:07:12 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp4.osuosl.org (Postfix) with ESMTP id 16CD24062F for ; Tue, 13 Jul 2021 18:07:11 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 243A61FB; Tue, 13 Jul 2021 11:07:11 -0700 (PDT) Received: from [10.57.36.240] (unknown [10.57.36.240]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C0FC43F7D8; Tue, 13 Jul 2021 11:07:05 -0700 (PDT) Subject: Re: [PATCH v2 0/3] iommu: Enable non-strict DMA on QCom SD/MMC To: Doug Anderson , Joerg Roedel References: <20210624171759.4125094-1-dianders@chromium.org> From: Robin Murphy Message-ID: Date: Tue, 13 Jul 2021 19:07:00 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-GB Cc: Ulf Hansson , Linux Doc Mailing List , Peter Zijlstra , linux-pci@vger.kernel.org, Konrad Dybcio , Thierry Reding , Joel Fernandes , Rajat Jain , Will Deacon , Rob Clark , Saravana Kannan , Jonathan Corbet , quic_c_gdjako@quicinc.com, Linux ARM , Viresh Kumar , Veerabhadrarao Badiganti , "Paul E. McKenney" , linux-arm-msm , Bjorn Helgaas , Sonny Rao , Vlastimil Babka , Randy Dunlap , Linux MMC List , Adrian Hunter , LKML , iommu@lists.linux-foundation.org, Andrew Morton , "Maciej W. Rozycki" X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On 2021-07-08 15:36, Doug Anderson wrote: [...] >> Or document for the users that want performance how to >> change the setting, so that they can decide. > > Pushing this to the users can make sense for a Linux distribution but > probably less sense for an embedded platform. So I'm happy to make > some way for a user to override this (like via kernel command line), > but I also strongly believe there should be a default that users don't > have to futz with that we think is correct. FYI I did make progress on the "punt it to userspace" approach. I'm not posting it even as an RFC yet because I still need to set up a machine to try actually testing any of it (it's almost certainly broken somewhere), but in the end it comes out looking surprisingly not too bad overall. If you're curious to take a look in the meantime I put it here: https://gitlab.arm.com/linux-arm/linux-rm/-/commits/iommu/fq Cheers, Robin. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu