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 5B90AC00A8F for ; Mon, 23 Oct 2023 22:00:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232127AbjJWWAa (ORCPT ); Mon, 23 Oct 2023 18:00:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59268 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231187AbjJWWA1 (ORCPT ); Mon, 23 Oct 2023 18:00:27 -0400 Received: from mx0b-00069f02.pphosted.com (mx0b-00069f02.pphosted.com [205.220.177.32]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2418F10C for ; Mon, 23 Oct 2023 15:00:25 -0700 (PDT) Received: from pps.filterd (m0246630.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 39NLi5H8020581; Mon, 23 Oct 2023 22:00:08 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=message-id : date : subject : to : cc : references : from : in-reply-to : content-type : content-transfer-encoding : mime-version; s=corp-2023-03-30; bh=UVCebi6LtFk4/FFQhC6ESOTBzDn3wdGAb+r05BzMr5E=; b=TCv52kwt4zjawX2nBZfsvnuNbUrnzm64kYhRQPWUTrx8uDAxm7vyukRmBKM7Ud27vuPt TRTyExywOEuSv/1c8BRObByXn4NiiSP3tbWPlznhrFPXPL28TYH2jaGr2ZgCdeTJqklQ nkbUVocHxvkhaERSt+LUxeXREuMeg3cxiFB/2oq0p2jI/3/Duwuo/zJ9GxZ837IVoyML p7mH6AtlklbeeveqgcvRtsTHw4oW8miRkI9eXdvIK7WNneHWvcQWeIenEZ3P42pd7FaX 3JO8us7E2Dy8umy8HbI0FczZ84/b/F4FeXvg7ZZC5k23gVUNYGZO5TW8jBDGl1aP7lEf jg== Received: from iadpaimrmta03.imrmtpd1.prodappiadaev1.oraclevcn.com (iadpaimrmta03.appoci.oracle.com [130.35.103.27]) by mx0b-00069f02.pphosted.com (PPS) with ESMTPS id 3tv52dv645-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 23 Oct 2023 22:00:07 +0000 Received: from pps.filterd (iadpaimrmta03.imrmtpd1.prodappiadaev1.oraclevcn.com [127.0.0.1]) by iadpaimrmta03.imrmtpd1.prodappiadaev1.oraclevcn.com (8.17.1.19/8.17.1.19) with ESMTP id 39NKx8FQ031095; Mon, 23 Oct 2023 22:00:07 GMT Received: from nam12-bn8-obe.outbound.protection.outlook.com (mail-bn8nam12lp2168.outbound.protection.outlook.com [104.47.55.168]) by iadpaimrmta03.imrmtpd1.prodappiadaev1.oraclevcn.com (PPS) with ESMTPS id 3tv53b2mr1-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 23 Oct 2023 22:00:06 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=ZfWR2G6BkPfV1HuuRB6YoTjqHmspIt7g9KLCUroD6mEKH0BRnDz8JkjsIYCl4kNy9DqMNbNF1KBKgJ7HzThvSFknurHYKh7m1MAgSs7FDCndy6TiWGRju7VlyJzDw7cDUlPDUGx6pOpkANOLTTt3NMvRKgRbp8+W9/SF9xti1PpztB/2AZNEYoBdRQjWzfERVmggrJk9Sv0agJ2Bj2pyEh+CrXSAuZmd4lckTXndonzTQptpsrSH7P1aNWhbiRwnpM2CDoGQxnS5EM6BEkgkXYqGlkNzAlSO7s7/9GhCcwAtr7gQ0bhxPDbk/I7Yr/xuTp1/bUlEE33nc/3TG/ecVw== 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=UVCebi6LtFk4/FFQhC6ESOTBzDn3wdGAb+r05BzMr5E=; b=k6xY5BczTaFMmhWPMpN1575NsBKkeKq21/gCjkilYhZtRdoee1xfjf/W+l8yJ/Max5LbNIjTZQnJr9oRVdHsplkxf7LH9FrJWz1byml/xVnBbu6f3W8MNRso4a2MUTapFCaMKQrHaBGrMSfvt5j7RpuOOQUaDkLlWft3cJYI4dW9ZKnea9XU7ADrJ5NkziYVPUksZXoUQbFN41jJH6lk37cJ2ZBaKPZQRJuOjHHEK+7zwpASaxbaX78XCwlB0+J/SvczR+/kwrkI1ND1VVKzUVVAWL4DULVID6x0wDosKTIARuvyHb+j3Zf3t0jMxS9YJ1TfWZjDI0ZOPjv8SyFB2Q== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=oracle.com; dmarc=pass action=none header.from=oracle.com; dkim=pass header.d=oracle.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.onmicrosoft.com; s=selector2-oracle-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=UVCebi6LtFk4/FFQhC6ESOTBzDn3wdGAb+r05BzMr5E=; b=X2D+CTt5W/466YpHa0+rNG5qGLgg1a/a9tf7knMqIgaoAVLZB2JoffaIkr0sbmyROLaBevWQydxOzm7eag3UcSycZB7zZIwHGD2ZT3fAWitZlJdjIqWpMkdsKnuWLoR0hjn/H8R/Vsi1DhN+cwhZSCl//hGOAsrSmORMNddbzD4= Received: from MW4PR10MB6535.namprd10.prod.outlook.com (2603:10b6:303:225::12) by DS7PR10MB5376.namprd10.prod.outlook.com (2603:10b6:5:3a9::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.6907.26; Mon, 23 Oct 2023 22:00:04 +0000 Received: from MW4PR10MB6535.namprd10.prod.outlook.com ([fe80::3942:c32c:7de0:d930]) by MW4PR10MB6535.namprd10.prod.outlook.com ([fe80::3942:c32c:7de0:d930%4]) with mapi id 15.20.6907.025; Mon, 23 Oct 2023 22:00:04 +0000 Message-ID: <4d03661b-4289-46e7-8760-32a186783b73@oracle.com> Date: Mon, 23 Oct 2023 15:00:01 -0700 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 0/7] vdpa: decouple reset of iotlb mapping from device reset Content-Language: en-US To: Jason Wang Cc: mst@redhat.com, eperezma@redhat.com, sgarzare@redhat.com, dtatulea@nvidia.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org References: <1697880319-4937-1-git-send-email-si-wei.liu@oracle.com> From: Si-Wei Liu Organization: Oracle Corporation In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: BY3PR05CA0002.namprd05.prod.outlook.com (2603:10b6:a03:254::7) To MW4PR10MB6535.namprd10.prod.outlook.com (2603:10b6:303:225::12) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MW4PR10MB6535:EE_|DS7PR10MB5376:EE_ X-MS-Office365-Filtering-Correlation-Id: 8c68c0f5-a0e0-4531-480a-08dbd41369af 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:MW4PR10MB6535.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230031)(376002)(396003)(136003)(366004)(346002)(39860400002)(230922051799003)(64100799003)(186009)(451199024)(1800799009)(31686004)(66899024)(6666004)(2906002)(4326008)(41300700001)(8676002)(26005)(6506007)(38100700002)(5660300002)(36916002)(6512007)(53546011)(83380400001)(2616005)(6486002)(8936002)(66556008)(31696002)(36756003)(6916009)(316002)(86362001)(66946007)(966005)(66476007)(478600001)(45980500001)(43740500002);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?MVczdk5Uazh3ZVZZcE5GcE5jKzFrUG5OYmsycElBaUVSbnBmUFRCMXBLRitS?= =?utf-8?B?cmlWTFJIaklIOTBxa2xZNitGOXlNd0xRTWtHM2FnSjYzRzJxZjRPeEhhU0Rn?= =?utf-8?B?RW5qZkhCRGhRNi9Ca3RmNXZMM1JjTVRyUFFiMXZrTnM3MU9scFhTSEZ3Sjcz?= =?utf-8?B?M2MrSWdJd0owM3ZDeUZidkptMStySjZGM05jd2FrT3lqSWRZcG5ES1hqSEg5?= =?utf-8?B?K2dyQXJQVnh3ZW1PcHNsK0RBdThITHRMZ1prcThtbkU0d1VzZndRM011blI4?= =?utf-8?B?LzI4MnhUYXpzSXdLcndMM1NoOFNiblI3RkFtRzRkcm0rdjF5aEk2QzAwYnYr?= =?utf-8?B?MVFhNTRPSnFQelMvbXNKYVlFL252M0lETGFSQTR6ak9pU0QvTlJ1U3pZYjJs?= =?utf-8?B?akVEUlpiT2xwOGRlM0pNMXExVVl6VEhBTWhhL3FoTFRXa24rMlhYZUJocTda?= =?utf-8?B?NnNHY0NIMk0vU3ROcFhZTkEwdTBVRTFLNFdGbDJZV3BHSTNnNjdzNGRGaFJ5?= =?utf-8?B?Ulh0S2oyU040UklGSjNjbXhJMDhvWHF1Z1c5aWlwbVo0UC9rbW9lSGdqdkpw?= =?utf-8?B?NmxGNW8zTG82aW1ZQkgvMDFyMkllalBjWEZ4UG1oeWcwLzhVSGhMY2NKM1pC?= =?utf-8?B?SktWcHdsQlBJS1ViWnc2RWcwdTNRdWtieXZlbXBJVmZZa0puVnd2T2RaeXNh?= =?utf-8?B?cHlLOWlBdlFMamE3MHlvZEFHbFo2QWxFSW5sQTJmbGlFOGFyc1RTY0V1VFp2?= =?utf-8?B?a3czbDlFMnF3QTVLSzJ1QnNkMnBleU5lSUd4SitjWEkrTXNObDRSL1diQUJD?= =?utf-8?B?T0F4c0IwR3VMVEozNmZZYU93dyt1RnVtdEYrSmtYMnNnL2NndHRSMklDNk45?= =?utf-8?B?bHMxeE1nb216bXhNYkVJNUVra0FOZW1QVE5xTzI3cU5FOEFWR0M1S2R2NWpB?= =?utf-8?B?YUpjUDhCNndUelh6QWxrOFA0K3ozZU04enhCMk5nWHRKdXZyVkVURkZhT0pt?= =?utf-8?B?akNqKzBkUEZvKzBUMVhTQ1Uwb1QxVFlLRmwvYVFWeXp1RkRLS3JGWnB0WVBw?= =?utf-8?B?QTVsTGJwWVVvaDNGZG5CSGNmZmtlYks4QWQ5UmZRR1ppbGNlQTBDT1F3MGdM?= =?utf-8?B?SXkzWmJSRjJ0ZlllVGM1TFpLN3R0bnA4MG8rTlQ5aTE0blh1SzZ3dFNsVDk5?= =?utf-8?B?RFVrclJNWTk5SG96K284Wm1YZ0o0eWVsS1FTb203K2JHYXVXVUFQcC8zdGxz?= =?utf-8?B?QnJ3OUw5eE9qc2p3d0RGbnJMVmlYbjlYeW9UZmJ2R3dXTmI5OGdQeldNVlRN?= =?utf-8?B?VmFPbFh6NmxFMkRuQS8rUTZFZ0F4NStIUHlqT01FYTd5clpLVjk3eEJUOWYw?= =?utf-8?B?dm9NRmpoTVZOS0ZDUmFRY1pkUURuSTJ2Uys1cmVLclpLTXlKc1d0QkswSmxC?= =?utf-8?B?TmYvRFRmckh0OEhnZWI0dXZNYXVTNDRYQVlnaVIzQVZFenZPTHJOaEpwSFht?= =?utf-8?B?dS85RnhmeVRIR29YUERWdG5pdFlBQmdKQzJlRGZDWWh1UW9pWUFRYld1bm1a?= =?utf-8?B?SWJnS3UrM2pNZFdmOG9IV3BiaUtoODlSMzA4NVhxK1Njdk1nalNJK25MQ1NI?= =?utf-8?B?TG5OLzhIeVhBOVgyc0xCMmpBOXBPTHhyZkh3OHl5MERDcklXTHo0VXR3QU5S?= =?utf-8?B?WkhjNzdXOWFwQ2MxekNUQlRJellkNDMzWW5DSTUwYjhKVFNQeko2SWhseGI1?= =?utf-8?B?ODh6ZU9JcmRuYmw3OVVIK0JIak54Y0l2aE9YMUhDblJBdVVPaUJXbEZ4TWJq?= =?utf-8?B?aVdDekRnWnRtaXdwc3FPSkVlTW9JY1dhM25jaEhJZkNlK2pIQVRJT2JuM1ZS?= =?utf-8?B?NVQyTkRsT0tJczZIWW1QdnhQVWxNY1h4eldMMDFEUC9lR0d2dzdaQmwvWWFQ?= =?utf-8?B?YTdrM0FZanU2NGd2V2J6SmkvZURIRU43SHQwY1NsZUttVnNmZWZqR09zdUhm?= =?utf-8?B?dXRoMzhNOG1uQklhdzRBRUNJcmJHMXJ6WnM5YUhTd0huaE5rbHNTL2plbHB6?= =?utf-8?B?WEpQLytVbjd6QWx3Ti9ta1pIZG1UOE9nS0RUckdEVEtVOURodGU5V2hpanVL?= =?utf-8?Q?Letp942AYmSheWyQzQGDVSIZ1?= X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: 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 X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-Network-Message-Id: 8c68c0f5-a0e0-4531-480a-08dbd41369af X-MS-Exchange-CrossTenant-AuthSource: MW4PR10MB6535.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Oct 2023 22:00:04.7687 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: Pkf4J04d0tNqBbqhr7hWFs3+wQABawEvi0EdNcYyPNBhrBCfnt82rwppWN0ysz/90LbhqC0+3u/D38kQjynw0Q== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR10MB5376 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.980,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-10-23_21,2023-10-19_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 malwarescore=0 mlxscore=0 suspectscore=0 spamscore=0 adultscore=0 mlxlogscore=999 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2310170001 definitions=main-2310230193 X-Proofpoint-ORIG-GUID: J7KMr18Ux7JNJBxV8FJhVnmrKtIfTn9_ X-Proofpoint-GUID: J7KMr18Ux7JNJBxV8FJhVnmrKtIfTn9_ Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/22/2023 8:51 PM, Jason Wang wrote: > Hi Si-Wei: > > On Sat, Oct 21, 2023 at 5:28 PM Si-Wei Liu wrote: >> In order to reduce needlessly high setup and teardown cost >> of iotlb mapping during live migration, it's crucial to >> decouple the vhost-vdpa iotlb abstraction from the virtio >> device life cycle, i.e. iotlb mappings should be left >> intact across virtio device reset [1]. For it to work, the >> on-chip IOMMU parent device could implement a separate >> .reset_map() operation callback to restore 1:1 DMA mapping >> without having to resort to the .reset() callback, the >> latter of which is mainly used to reset virtio device state. >> This new .reset_map() callback will be invoked only before >> the vhost-vdpa driver is to be removed and detached from >> the vdpa bus, such that other vdpa bus drivers, e.g. >> virtio-vdpa, can start with 1:1 DMA mapping when they >> are attached. For the context, those on-chip IOMMU parent >> devices, create the 1:1 DMA mapping at vdpa device creation, >> and they would implicitly destroy the 1:1 mapping when >> the first .set_map or .dma_map callback is invoked. >> >> This patchset is rebased on top of the latest vhost tree. >> >> [1] Reducing vdpa migration downtime because of memory pin / maps >> https://www.mail-archive.com/qemu-devel@nongnu.org/msg953755.html >> >> --- >> v4: >> - Rework compatibility using new .compat_reset driver op > I still think having a set_backend_feature() This will overload backend features with the role of carrying over compatibility quirks, which I tried to avoid from. While I think the .compat_reset from the v4 code just works with the backend features acknowledgement (and maybe others as well) to determine, but not directly tie it to backend features itself. These two have different implications in terms of requirement, scope and maintaining/deprecation, better to cope with compat quirks in explicit and driver visible way. > or reset_map(clean=true) might be better. An explicit op might be marginally better in driver writer's point of view. Compliant driver doesn't have to bother asserting clean_map never be true so their code would never bother dealing with this case, as explained in the commit log for patch 5 "vhost-vdpa: clean iotlb map during reset for older userspace": "     The separation of .compat_reset from the regular .reset allows     vhost-vdpa able to know which driver had broken behavior before, so it     can apply the corresponding compatibility quirk to the individual driver     whenever needed.  Compared to overloading the existing .reset with     flags, .compat_reset won't cause any extra burden to the implementation     of every compliant driver. " > As it tries hard to not introduce new stuff on the bus. Honestly I don't see substantial difference between these other than the color. There's no single best solution that stands out among the 3. And I assume you already noticed it from all the above 3 approaches will have to go with backend features negotiation, that the 1st vdpa reset before backend feature negotiation will use the compliant version of .reset that doesn't clean up the map. While I don't think this nuance matters much to existing older userspace apps, as the maps should already get cleaned by previous process in vhost_vdpa_cleanup(), but if bug-for-bug behavioral compatibility is what you want, module parameter will be the single best answer. Regards, -Siwei > But we can listen to others for sure. > > Thanks >