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 Received: from smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 957BCC433F5 for ; Wed, 23 Feb 2022 18:20:48 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id 4B44440116; Wed, 23 Feb 2022 18:20:48 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id KPZFtf4saIJz; Wed, 23 Feb 2022 18:20:47 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [IPv6:2605:bc80:3010:104::8cd3:938]) by smtp2.osuosl.org (Postfix) with ESMTPS id F2AF7404FD; Wed, 23 Feb 2022 18:20:46 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id C6D60C0021; Wed, 23 Feb 2022 18:20:46 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [IPv6:2605:bc80:3010::138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 55353C0011 for ; Wed, 23 Feb 2022 18:20:46 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 35C6582ADD for ; Wed, 23 Feb 2022 18:20:46 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 8lpcGv4S_jjx for ; Wed, 23 Feb 2022 18:20:45 +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 smtp1.osuosl.org (Postfix) with ESMTP id 7F03182AC8 for ; Wed, 23 Feb 2022 18:20:45 +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 B22C8D6E; Wed, 23 Feb 2022 10:20:44 -0800 (PST) Received: from [10.57.40.147] (unknown [10.57.40.147]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 23D623F70D; Wed, 23 Feb 2022 10:20:41 -0800 (PST) Message-ID: <2114e6e6-68cc-4552-8781-0a824de2c0de@arm.com> Date: Wed, 23 Feb 2022 18:20:36 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Subject: Re: [PATCH v6 01/11] iommu: Add dma ownership management interfaces Content-Language: en-GB To: Jason Gunthorpe References: <20220218005521.172832-1-baolu.lu@linux.intel.com> <20220218005521.172832-2-baolu.lu@linux.intel.com> <20220223180244.GA390403@nvidia.com> From: Robin Murphy In-Reply-To: <20220223180244.GA390403@nvidia.com> Cc: Stuart Yoder , rafael@kernel.org, David Airlie , linux-pci@vger.kernel.org, Thierry Reding , Diana Craciun , Dmitry Osipenko , Will Deacon , Ashok Raj , Jonathan Hunter , Christoph Hellwig , Kevin Tian , Chaitanya Kulkarni , Alex Williamson , kvm@vger.kernel.org, Bjorn Helgaas , Dan Williams , Greg Kroah-Hartman , Cornelia Huck , linux-kernel@vger.kernel.org, Li Yang , iommu@lists.linux-foundation.org, Jacob jun Pan , Daniel Vetter 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 2022-02-23 18:02, Jason Gunthorpe via iommu wrote: > On Wed, Feb 23, 2022 at 06:00:06PM +0000, Robin Murphy wrote: > >> ...and equivalently just set owner_cnt directly to 0 here. I don't see a >> realistic use-case for any driver to claim the same group more than once, >> and allowing it in the API just feels like opening up various potential >> corners for things to get out of sync. > > I am Ok if we toss it out to get this merged, as there is no in-kernel > user right now. > > Something will have to come back for iommufd, but we can look at what > is best suited then. If iommufd plans to be too dumb to keep track of whether it already owns a given group or not, I can't see it dealing with attaching that group to a single domain no more than once, either ;) Robin. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu