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 72337C43217 for ; Mon, 14 Feb 2022 15:46:38 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 1631682890; Mon, 14 Feb 2022 15:46:38 +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 8d2AXeD3Y-rs; Mon, 14 Feb 2022 15:46:37 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp1.osuosl.org (Postfix) with ESMTPS id 06CD682897; Mon, 14 Feb 2022 15:46:36 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id CA6DCC001A; Mon, 14 Feb 2022 15:46:36 +0000 (UTC) Received: from smtp2.osuosl.org (smtp2.osuosl.org [IPv6:2605:bc80:3010::133]) by lists.linuxfoundation.org (Postfix) with ESMTP id A2A8EC000B for ; Mon, 14 Feb 2022 15:46:35 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id 8090F40177 for ; Mon, 14 Feb 2022 15:46:35 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Authentication-Results: smtp2.osuosl.org (amavisd-new); dkim=pass (2048-bit key) header.d=nvidia.com 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 f4hMni55679s for ; Mon, 14 Feb 2022 15:46:34 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.8.0 Received: from NAM12-BN8-obe.outbound.protection.outlook.com (mail-bn8nam12on20600.outbound.protection.outlook.com [IPv6:2a01:111:f400:fe5b::600]) by smtp2.osuosl.org (Postfix) with ESMTPS id E586D400A4 for ; Mon, 14 Feb 2022 15:46:33 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=WBUx11nm1limaV6Gigylear8n+1NcR7CQZpQJCri+a93uycig8RHM18RlKYDs7wbCurr6JomAUXjyJhiBUEp/7QBh5EJaY1rDlBXanMD3ujg902O8EJXOidRnQt2Hoszs6YSRFNSXkLVVDjPzZsHJLGLF1pL9ysHIiXV3zMLL+Muv35DuhM9vNw04o4PoXx3rHW0LmrMnPr9IVDxSzfJ/bBWXQ7PBOOA2c+Ny3k65LdQjYAnpbG8bkNbtmwuT1LzW3SSi9B2+NLWvaECSdxPa/pVlA2AO9H1khxYFBijTaDeGRsitL8x/1AEiYLG7oPGZj6vtdYmR9NtM8iGww2YvA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=2wsG1hr8343sJCB58vClGdnUh/toyAKtwzcI63W5/LM=; b=nN2PSia7T+EqLQw0x7QXNgcxTe7APktp/K25gxUrn2GPMirmDbPmOq7zLdwKpYMncQYlAqmlLqJ3q+IE3RY5v4SlmlcqF9RuIbox42o0NjSJymH6RFdbQNRC2yi31+rRwNuUu7gEc/BNlcHwjpjE2Tw4LRdU76e1zB0El7XFfpts3M+wfwY2WlUvrBYOEpa5lyVSgBJ/5hum6fJ8ik0g0vWEAlppypvG5NF+6oypIrWnDzV34Dn4aJgCEJNTXFQqxJ9zFkf2hlxL2646XKIaLmnfVu9ssqzXp9En9DEr13Wwo67g/RBvinY8vKkIfdEHjLUSH/Ab3CIDwXIg+ZCjCA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=none; dmarc=none; dkim=none; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=2wsG1hr8343sJCB58vClGdnUh/toyAKtwzcI63W5/LM=; b=LCB5/rG1HRF82NkcPPsmdTlsEtgAVKbBEZCUNbjsdrkEGD0i/JbZ0XpE7wil02qTg30lzqiFFtIRUR2SOnPEqXZA731jrt6vkQ97fkCsD5JDBli0FozSmv57RcMgYta42fxJpeTnVC5Yq1f8WcsFDlJGlgLoq52KRJ1MUsZCr1Ii4gYUMH9u+p9FY//STG0OenjbNx21m7xTmiDNjFmI8OOE1+XDFxf80Er5owFuCiIY3ipiqJT9ee/ITtlnVN+oGgl1vlE6zuF3gXIFy9mXTXggT4lQaDjt6DQYXjFWO1fHRYddlibQtt55nvXPEMiYwGHdxHijqCC0Q3VXvL7Dwg== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from MN2PR12MB4192.namprd12.prod.outlook.com (2603:10b6:208:1d5::15) by DM6PR12MB3770.namprd12.prod.outlook.com (2603:10b6:5:1c4::19) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4975.19; Mon, 14 Feb 2022 15:46:27 +0000 Received: from MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::e8f4:9793:da37:1bd3]) by MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::e8f4:9793:da37:1bd3%4]) with mapi id 15.20.4975.019; Mon, 14 Feb 2022 15:46:27 +0000 Date: Mon, 14 Feb 2022 11:46:26 -0400 To: Robin Murphy Subject: Re: [PATCH v1 3/8] iommu: Extend iommu_at[de]tach_device() for multi-device groups Message-ID: <20220214154626.GF4160@nvidia.com> References: <20220106022053.2406748-1-baolu.lu@linux.intel.com> <20220106022053.2406748-4-baolu.lu@linux.intel.com> <20220214130313.GV4160@nvidia.com> <08e90a61-8491-acf1-ab0f-f93f97366d24@arm.com> Content-Disposition: inline In-Reply-To: <08e90a61-8491-acf1-ab0f-f93f97366d24@arm.com> X-ClientProxiedBy: BL1PR13CA0131.namprd13.prod.outlook.com (2603:10b6:208:2bb::16) To MN2PR12MB4192.namprd12.prod.outlook.com (2603:10b6:208:1d5::15) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 22f3bb6a-1def-45e7-df32-08d9efd1295d X-MS-TrafficTypeDiagnostic: DM6PR12MB3770:EE_ X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:10000; X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255; CTRY:; LANG:en; SCL:1; SRV:; IPV:NLI; SFV:NSPM; H:MN2PR12MB4192.namprd12.prod.outlook.com; PTR:; CAT:NONE; SFS:(13230001)(4636009)(366004)(6916009)(54906003)(6506007)(316002)(508600001)(6486002)(86362001)(6512007)(1076003)(5660300002)(26005)(186003)(2906002)(33656002)(2616005)(36756003)(8676002)(4326008)(66476007)(66556008)(66946007)(8936002)(7416002)(38100700002); DIR:OUT; SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?rm3A8/+CCwywTETbcpetS1LxfwHQG9kU7qGb1ZgSuuTD74K8pFUjNa+JrHTi?= =?us-ascii?Q?PHWnR0h3AI4D2/8HgIigcEA8YMQFqDW6uQ0yYoPzBQPhvXXy++R7MuPS6dYb?= =?us-ascii?Q?5jCV2UohLGmFhgakv9NbWYN/XVMZRZq3W4F71moCrYSPX2JOOebkr1mRfLrd?= =?us-ascii?Q?hCex6ySGDOOBkAqgaiASbZkCchsonRiRbCoXQu9R6VMDHYuEXyA6U0YHXoiB?= =?us-ascii?Q?8heg1xHiyFN44A8uuONby5YSqOlQKcyCfUkkdvCx8NKELdcICrEE35UdoBgw?= =?us-ascii?Q?IYCUHAu+nkPGRHwQoAXj+pmc/5lhSyoae5e6Q2amcOiEP6PTdFV9AB05CpqY?= =?us-ascii?Q?66/LwKNyasYIS45E4+R9IywSGwk0IocN/4YqCNcyi8JNTnuXwNE5BOtz6M7x?= =?us-ascii?Q?PMFm4gnKjc/o9F3ZEt+AF4/bNWuJntxT6t+0vbDhIa0/I8gRZndaqGvSjkHa?= =?us-ascii?Q?KV0sBPl99bYFxVQwEsQaRCH2bBFmWIqp8DpNhbIXtLU9qUNlsJuAu3QgJFGK?= =?us-ascii?Q?H0Tc0MC0ZmHzTk1S0Yq1sc2EHJ0e2brh8tEkLQcprqy4qh9AV3jYDsqHO8po?= =?us-ascii?Q?9WAjNBP+FvQcOeN/ySfwet57sNUiB8ppNhJ9n+Tm6xb13dWp7yOjtMMx2x41?= =?us-ascii?Q?s+1zXLYVaKSQy+8xiGLH5QyF2SvOHRH0jObtZfyF3nxMTL7KfqWrO0ftSBP6?= =?us-ascii?Q?5XCNngDHWsos1aKJuzvDEWKqORG2f50tMBEuVvExK8SyvTEnBPZ+to2oGnit?= =?us-ascii?Q?A2eST6XNQTljlD01mRZENJHVI8Qv7zxco4QtAFmHdQRZvOK9KEelzte2kmik?= =?us-ascii?Q?6HhPeX2e9912L5YOPTfceCpLr/94GkIDa9B6/Xi7Dt6Nb5SeNDlvNFizYZ2L?= =?us-ascii?Q?/8EtrG6q9AMk0DN+49DQyuNlWJjGpJNaWvDuhsL3lqTD52mBXUQxkly+d1fY?= =?us-ascii?Q?/Af8dYUqA/eLFz5GelxwblWfpjbK3fUuuGH1e2zj2JjsIo05Zlx7n0nFkE2B?= =?us-ascii?Q?M2M2x5mHDr0vb1FN6/hUwioeGfPV/cVlXo1MyZJ+Om6lwNcsImoE997PJj38?= =?us-ascii?Q?ukcQhg5L6L4RdQKHUQnv7lzqfNgGy2hkoFLIYfDBhsRJzgEYdp9q/nbEdiSz?= =?us-ascii?Q?/8j6xEGL1lnqGGYrIwR/Y5C1RxBp7fJNqiVbEdhyooUzT/DJP7LSO0ED0ZFG?= =?us-ascii?Q?UwEZ2/EogS953P5B7OBK/Em+EypZbiEYBok2eegPoxfo8KOfTBg8+wWrkynI?= =?us-ascii?Q?SEhbkKioM9NIeMf0eeVAjkqveePOP++kGlcF60nrzRjfJj/TLpnsvyKmvNU7?= =?us-ascii?Q?LYJ2FR4YhLLaE5oBjuAvoyIco1iJq2agV1UpZz+ZSYHrj6E3G6RlZT4B9wzV?= =?us-ascii?Q?H8ON8NlljGibM2SpEOGq2GoO/NVhQkVPRd8Ws9+ra++HTEFePpGuvvG597Rw?= =?us-ascii?Q?r4GO3xtWC0hUzTZ00b94fsWrIvS3RK32synSBI33PX2XRjyVZWjej8Xf04Yv?= =?us-ascii?Q?e7p8KirtDlRlMNKq5ruZDI/0UwCkUH2UvUa/I3iadg8com7j7Cg8Je5M4CVx?= =?us-ascii?Q?5S3MgbZ/4eJ9sRmBkZE=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 22f3bb6a-1def-45e7-df32-08d9efd1295d X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB4192.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Feb 2022 15:46:27.2419 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 2KIFVwNSONGNkzGqLzumqpOVl9sbJ9gs8IpLjf1TI9By3zan4o7rRMiv+QErA/ND X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB3770 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: , From: Jason Gunthorpe via iommu Reply-To: Jason Gunthorpe Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Mon, Feb 14, 2022 at 03:18:31PM +0000, Robin Murphy wrote: > Arguably, iommu_attach_device() could be renamed something like > iommu_attach_group_for_dev(), since that's effectively the semantic that all > the existing API users want anyway (even VFIO at the high level - the group > is the means for the user to assign their GPU/NIC/whatever device to their > process, not the end in itself). That's just a lot more churn. Right > It's not that callers should be blind to the entire concept of groups > altogether - they remain a significant reason why iommu_attach_device() > might fail, for one thing - however what callers really shouldn't need to be > bothered with is the exact *implementation* of groups. I do actually quite > like the idea of refining the group abstraction into isolation groups as a > superset of alias groups, but if anything that's a further argument for not > having the guts of the current abstraction exposed in places that don't need > to care - otherwise that would be liable to be a microcosm of this series in > itself: widespread churn vs. "same name, new meaning" compromises. Exactly, groups should not leak out through the abstraction more than necessary. If the caller can't do anything with the group information then it shouldn't touch it. VFIO needs them because its uAPI is tied, but even so we keep talking about ways to narrow the amount of group API it consumes. We should not set the recommended/good kAPI based on VFIOs uAPI design. Jason _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C9AD9C433EF for ; Mon, 14 Feb 2022 15:46:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1356020AbiBNPql (ORCPT ); Mon, 14 Feb 2022 10:46:41 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:40994 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1356016AbiBNPqk (ORCPT ); Mon, 14 Feb 2022 10:46:40 -0500 Received: from NAM12-BN8-obe.outbound.protection.outlook.com (mail-bn8nam12on2063.outbound.protection.outlook.com [40.107.237.63]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A28E826D; Mon, 14 Feb 2022 07:46:32 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=WBUx11nm1limaV6Gigylear8n+1NcR7CQZpQJCri+a93uycig8RHM18RlKYDs7wbCurr6JomAUXjyJhiBUEp/7QBh5EJaY1rDlBXanMD3ujg902O8EJXOidRnQt2Hoszs6YSRFNSXkLVVDjPzZsHJLGLF1pL9ysHIiXV3zMLL+Muv35DuhM9vNw04o4PoXx3rHW0LmrMnPr9IVDxSzfJ/bBWXQ7PBOOA2c+Ny3k65LdQjYAnpbG8bkNbtmwuT1LzW3SSi9B2+NLWvaECSdxPa/pVlA2AO9H1khxYFBijTaDeGRsitL8x/1AEiYLG7oPGZj6vtdYmR9NtM8iGww2YvA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=2wsG1hr8343sJCB58vClGdnUh/toyAKtwzcI63W5/LM=; b=nN2PSia7T+EqLQw0x7QXNgcxTe7APktp/K25gxUrn2GPMirmDbPmOq7zLdwKpYMncQYlAqmlLqJ3q+IE3RY5v4SlmlcqF9RuIbox42o0NjSJymH6RFdbQNRC2yi31+rRwNuUu7gEc/BNlcHwjpjE2Tw4LRdU76e1zB0El7XFfpts3M+wfwY2WlUvrBYOEpa5lyVSgBJ/5hum6fJ8ik0g0vWEAlppypvG5NF+6oypIrWnDzV34Dn4aJgCEJNTXFQqxJ9zFkf2hlxL2646XKIaLmnfVu9ssqzXp9En9DEr13Wwo67g/RBvinY8vKkIfdEHjLUSH/Ab3CIDwXIg+ZCjCA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=none; dmarc=none; dkim=none; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=2wsG1hr8343sJCB58vClGdnUh/toyAKtwzcI63W5/LM=; b=LCB5/rG1HRF82NkcPPsmdTlsEtgAVKbBEZCUNbjsdrkEGD0i/JbZ0XpE7wil02qTg30lzqiFFtIRUR2SOnPEqXZA731jrt6vkQ97fkCsD5JDBli0FozSmv57RcMgYta42fxJpeTnVC5Yq1f8WcsFDlJGlgLoq52KRJ1MUsZCr1Ii4gYUMH9u+p9FY//STG0OenjbNx21m7xTmiDNjFmI8OOE1+XDFxf80Er5owFuCiIY3ipiqJT9ee/ITtlnVN+oGgl1vlE6zuF3gXIFy9mXTXggT4lQaDjt6DQYXjFWO1fHRYddlibQtt55nvXPEMiYwGHdxHijqCC0Q3VXvL7Dwg== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from MN2PR12MB4192.namprd12.prod.outlook.com (2603:10b6:208:1d5::15) by DM6PR12MB3770.namprd12.prod.outlook.com (2603:10b6:5:1c4::19) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4975.19; Mon, 14 Feb 2022 15:46:27 +0000 Received: from MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::e8f4:9793:da37:1bd3]) by MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::e8f4:9793:da37:1bd3%4]) with mapi id 15.20.4975.019; Mon, 14 Feb 2022 15:46:27 +0000 Date: Mon, 14 Feb 2022 11:46:26 -0400 From: Jason Gunthorpe To: Robin Murphy Cc: Joerg Roedel , 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 Subject: Re: [PATCH v1 3/8] iommu: Extend iommu_at[de]tach_device() for multi-device groups Message-ID: <20220214154626.GF4160@nvidia.com> References: <20220106022053.2406748-1-baolu.lu@linux.intel.com> <20220106022053.2406748-4-baolu.lu@linux.intel.com> <20220214130313.GV4160@nvidia.com> <08e90a61-8491-acf1-ab0f-f93f97366d24@arm.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <08e90a61-8491-acf1-ab0f-f93f97366d24@arm.com> X-ClientProxiedBy: BL1PR13CA0131.namprd13.prod.outlook.com (2603:10b6:208:2bb::16) To MN2PR12MB4192.namprd12.prod.outlook.com (2603:10b6:208:1d5::15) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 22f3bb6a-1def-45e7-df32-08d9efd1295d X-MS-TrafficTypeDiagnostic: DM6PR12MB3770:EE_ X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:10000; X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:MN2PR12MB4192.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230001)(4636009)(366004)(6916009)(54906003)(6506007)(316002)(508600001)(6486002)(86362001)(6512007)(1076003)(5660300002)(26005)(186003)(2906002)(33656002)(2616005)(36756003)(8676002)(4326008)(66476007)(66556008)(66946007)(8936002)(7416002)(38100700002);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?rm3A8/+CCwywTETbcpetS1LxfwHQG9kU7qGb1ZgSuuTD74K8pFUjNa+JrHTi?= =?us-ascii?Q?PHWnR0h3AI4D2/8HgIigcEA8YMQFqDW6uQ0yYoPzBQPhvXXy++R7MuPS6dYb?= =?us-ascii?Q?5jCV2UohLGmFhgakv9NbWYN/XVMZRZq3W4F71moCrYSPX2JOOebkr1mRfLrd?= =?us-ascii?Q?hCex6ySGDOOBkAqgaiASbZkCchsonRiRbCoXQu9R6VMDHYuEXyA6U0YHXoiB?= =?us-ascii?Q?8heg1xHiyFN44A8uuONby5YSqOlQKcyCfUkkdvCx8NKELdcICrEE35UdoBgw?= =?us-ascii?Q?IYCUHAu+nkPGRHwQoAXj+pmc/5lhSyoae5e6Q2amcOiEP6PTdFV9AB05CpqY?= =?us-ascii?Q?66/LwKNyasYIS45E4+R9IywSGwk0IocN/4YqCNcyi8JNTnuXwNE5BOtz6M7x?= =?us-ascii?Q?PMFm4gnKjc/o9F3ZEt+AF4/bNWuJntxT6t+0vbDhIa0/I8gRZndaqGvSjkHa?= =?us-ascii?Q?KV0sBPl99bYFxVQwEsQaRCH2bBFmWIqp8DpNhbIXtLU9qUNlsJuAu3QgJFGK?= =?us-ascii?Q?H0Tc0MC0ZmHzTk1S0Yq1sc2EHJ0e2brh8tEkLQcprqy4qh9AV3jYDsqHO8po?= =?us-ascii?Q?9WAjNBP+FvQcOeN/ySfwet57sNUiB8ppNhJ9n+Tm6xb13dWp7yOjtMMx2x41?= =?us-ascii?Q?s+1zXLYVaKSQy+8xiGLH5QyF2SvOHRH0jObtZfyF3nxMTL7KfqWrO0ftSBP6?= =?us-ascii?Q?5XCNngDHWsos1aKJuzvDEWKqORG2f50tMBEuVvExK8SyvTEnBPZ+to2oGnit?= =?us-ascii?Q?A2eST6XNQTljlD01mRZENJHVI8Qv7zxco4QtAFmHdQRZvOK9KEelzte2kmik?= =?us-ascii?Q?6HhPeX2e9912L5YOPTfceCpLr/94GkIDa9B6/Xi7Dt6Nb5SeNDlvNFizYZ2L?= =?us-ascii?Q?/8EtrG6q9AMk0DN+49DQyuNlWJjGpJNaWvDuhsL3lqTD52mBXUQxkly+d1fY?= =?us-ascii?Q?/Af8dYUqA/eLFz5GelxwblWfpjbK3fUuuGH1e2zj2JjsIo05Zlx7n0nFkE2B?= =?us-ascii?Q?M2M2x5mHDr0vb1FN6/hUwioeGfPV/cVlXo1MyZJ+Om6lwNcsImoE997PJj38?= =?us-ascii?Q?ukcQhg5L6L4RdQKHUQnv7lzqfNgGy2hkoFLIYfDBhsRJzgEYdp9q/nbEdiSz?= =?us-ascii?Q?/8j6xEGL1lnqGGYrIwR/Y5C1RxBp7fJNqiVbEdhyooUzT/DJP7LSO0ED0ZFG?= =?us-ascii?Q?UwEZ2/EogS953P5B7OBK/Em+EypZbiEYBok2eegPoxfo8KOfTBg8+wWrkynI?= =?us-ascii?Q?SEhbkKioM9NIeMf0eeVAjkqveePOP++kGlcF60nrzRjfJj/TLpnsvyKmvNU7?= =?us-ascii?Q?LYJ2FR4YhLLaE5oBjuAvoyIco1iJq2agV1UpZz+ZSYHrj6E3G6RlZT4B9wzV?= =?us-ascii?Q?H8ON8NlljGibM2SpEOGq2GoO/NVhQkVPRd8Ws9+ra++HTEFePpGuvvG597Rw?= =?us-ascii?Q?r4GO3xtWC0hUzTZ00b94fsWrIvS3RK32synSBI33PX2XRjyVZWjej8Xf04Yv?= =?us-ascii?Q?e7p8KirtDlRlMNKq5ruZDI/0UwCkUH2UvUa/I3iadg8com7j7Cg8Je5M4CVx?= =?us-ascii?Q?5S3MgbZ/4eJ9sRmBkZE=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 22f3bb6a-1def-45e7-df32-08d9efd1295d X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB4192.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Feb 2022 15:46:27.2419 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 2KIFVwNSONGNkzGqLzumqpOVl9sbJ9gs8IpLjf1TI9By3zan4o7rRMiv+QErA/ND X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB3770 Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Mon, Feb 14, 2022 at 03:18:31PM +0000, Robin Murphy wrote: > Arguably, iommu_attach_device() could be renamed something like > iommu_attach_group_for_dev(), since that's effectively the semantic that all > the existing API users want anyway (even VFIO at the high level - the group > is the means for the user to assign their GPU/NIC/whatever device to their > process, not the end in itself). That's just a lot more churn. Right > It's not that callers should be blind to the entire concept of groups > altogether - they remain a significant reason why iommu_attach_device() > might fail, for one thing - however what callers really shouldn't need to be > bothered with is the exact *implementation* of groups. I do actually quite > like the idea of refining the group abstraction into isolation groups as a > superset of alias groups, but if anything that's a further argument for not > having the guts of the current abstraction exposed in places that don't need > to care - otherwise that would be liable to be a microcosm of this series in > itself: widespread churn vs. "same name, new meaning" compromises. Exactly, groups should not leak out through the abstraction more than necessary. If the caller can't do anything with the group information then it shouldn't touch it. VFIO needs them because its uAPI is tied, but even so we keep talking about ways to narrow the amount of group API it consumes. We should not set the recommended/good kAPI based on VFIOs uAPI design. Jason