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=-6.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,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 71E0BC07E96 for ; Tue, 13 Jul 2021 18:09:16 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 30BB461374 for ; Tue, 13 Jul 2021 18:09:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 30BB461374 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=jaCkDRsp8+tw/OZrbgQmRKqlpLi6EX8WKCERLCCN+wQ=; b=T4UXj42E3YazCJK7Vo5xP6/dko mpqrWNI/k9bS/Ywt6l7i/Dnuw7zPIvVSJKUFM659Qtc+Wd4nSuVcyAc6O1uXMWPxdW4YMbJrWGPK2 BoEv04NCvptrlL1MB5LUw/2MOExhUR2YbotXzqq4qKdubNVopKOFzlULag4ywNj40n2V9LhgMu6wx TCuE5W4yNYzAH7BYeA+YomO6uQgKTian92HF/hIJT2r2IOrCYX96urS50AbgRzeG9blYHkqJlWpxq Vs0Rsv/fkJ4v2ZFmJvQjZz3YzM4CuIcfdEKMB+E9IxjiQlbGq25P7tSGm9CcssCb8YYM+Mj1PgHIj z+sdL6dg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1m3MoT-00B77y-Cw; Tue, 13 Jul 2021 18:07:21 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1m3MoO-00B73P-Jj for linux-arm-kernel@lists.infradead.org; Tue, 13 Jul 2021 18:07:18 +0000 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210713_110716_777472_345B86EF X-CRM114-Status: GOOD ( 17.17 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Ulf Hansson , Linux Doc Mailing List , Peter Zijlstra , linux-pci@vger.kernel.org, Konrad Dybcio , Jordan Crouse , Thierry Reding , Joel Fernandes , Rajat Jain , Will Deacon , Rob Clark , Sai Prakash Ranjan , Saravana Kannan , Jonathan Corbet , Joerg Roedel , quic_c_gdjako@quicinc.com, Linux ARM , Viresh Kumar , Veerabhadrarao Badiganti , "Paul E. McKenney" , linux-arm-msm , John Garry , Nicolin Chen , Bjorn Helgaas , Bjorn Andersson , Sonny Rao , Vlastimil Babka , Randy Dunlap , Linux MMC List , Adrian Hunter , LKML , iommu@lists.linux-foundation.org, Andrew Morton , "Maciej W. Rozycki" Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel