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 smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (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 5D9AFC4332F for ; Thu, 24 Feb 2022 08:58:51 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 0B91681313; Thu, 24 Feb 2022 08:58:51 +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 PH1_v-3_H-L2; Thu, 24 Feb 2022 08:58:50 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp1.osuosl.org (Postfix) with ESMTPS id D33D38131F; Thu, 24 Feb 2022 08:58:49 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 871A6C001A; Thu, 24 Feb 2022 08:58:49 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [IPv6:2605:bc80:3010::138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 52CE4C0011 for ; Thu, 24 Feb 2022 08:58:48 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 2CD848131F for ; Thu, 24 Feb 2022 08:58:48 +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 xWVmx_o9uQqJ for ; Thu, 24 Feb 2022 08:58:47 +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 020EC81313 for ; Thu, 24 Feb 2022 08:58:46 +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 21F78D6E; Thu, 24 Feb 2022 00:58:46 -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 73E543F70D; Thu, 24 Feb 2022 00:58:40 -0800 (PST) Message-ID: <31dc9d19-362d-4c1a-1483-cc7f525c6dd3@arm.com> Date: Thu, 24 Feb 2022 08:58:36 +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: Lu Baolu , 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: 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 2022-02-24 05:29, Lu Baolu wrote: > On 2/24/22 1:16 PM, Lu Baolu wrote: >> Hi Robin and Jason, >> >> On 2/24/22 2:02 AM, Jason Gunthorpe 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. >> >> So we don't need the owner pointer in the API anymore, right? > > Oh, NO. > > The owner token represents that the group has been claimed for user > space access. And the default domain auto-attach policy will be changed > accordingly. > > So we still need this. Sorry for the noise. Exactly. In fact we could almost go the other way, and rename owner_cnt to dma_api_users and make it mutually exclusive with owner being set, but that's really just cosmetic. It's understandable enough as-is that owner_cnt > 0 with owner == NULL represents implicit DMA API ownership. Cheers, Robin. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu