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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 33B4AC88E45 for ; Fri, 11 Sep 2026 14:31:13 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 449616B009B; Fri, 11 Sep 2026 10:31:12 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 420766B009D; Fri, 11 Sep 2026 10:31:12 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3369F6B009E; Fri, 11 Sep 2026 10:31:12 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id ED04F6B009B for ; Fri, 11 Sep 2026 10:31:11 -0400 (EDT) Received: from smtpin20.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 348B2120260 for ; Fri, 11 Sep 2026 14:31:11 +0000 (UTC) X-FDA: 85201718742.20.A2FEFB6 Received: from SN4PR2101CU001.outbound.protection.outlook.com (mail-southcentralusazon11012003.outbound.protection.outlook.com [40.93.195.3]) by imf22.hostedemail.com (Postfix) with ESMTP id 48463C0009 for ; Fri, 11 Sep 2026 14:31:08 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=D1rBB3gg; spf=pass (imf22.hostedemail.com: domain of jgg@nvidia.com designates 40.93.195.3 as permitted sender) smtp.mailfrom=jgg@nvidia.com; dmarc=pass (policy=reject) header.from=nvidia.com; arc=pass ("microsoft.com:s=arcselector10001:i=1") ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1789137068; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=6JWgc0q+12jv5kIAv32LIGY1YmVkec7CyzTR2C4Uiww=; b=D2+5+bpaiUFK2s9HQYQNcF0+MlCYK69EbH44JdqwM2rF6WVs60oNr3YZuBBH/3EAWQEoeF eDNhwrYukjcQM7L4Yhi3OKt2Nx49aqvn7Jx7R2PwJ2Hurho3gmlGXhyBZFesBRmOKWu64X gFooLb1XBHr5wxzXUwH+3dwc1Ox0eKQ= ARC-Seal: i=2; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=pass; t=1789137068; b=v3fpD0ppnvQUR1uQE6FL/5TI3xRy5T7cGPlFOYvh4uilUpr1FecP1FMYjSG0Xj2/CDPpni j59dAFcrq1uKtXaUOP5JgbHfyNAzETkaXJ1G+6bKUpzAFO0fXgpxJIm/y1lcZUjAqQlHk/ +pBnsfaVzvhE3WqGiU4d/Sjmd46j8og= ARC-Authentication-Results: i=2; imf22.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=D1rBB3gg; spf=pass (imf22.hostedemail.com: domain of jgg@nvidia.com designates 40.93.195.3 as permitted sender) smtp.mailfrom=jgg@nvidia.com; dmarc=pass (policy=reject) header.from=nvidia.com; arc=pass ("microsoft.com:s=arcselector10001:i=1") ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=JatsJRqu1DoHoOvTrc8FauQKfwRXHbMCKMglcFr7kTTZgUkOtgQ0z1ZyXCWYV3oeGb5V/PwqlVE8ShlCazZcMoz30r+2dmC2pslOpAGzZrJP8WE5rRExP82KRgK9rueFGRD7aNx6/KjZ7YsOWZ6qzJW4g5ag+lWnG60EhncqtwAa5kyhWE2f6ZUpQMLhJetGRucshxdXMCdJz0ZyF5mmFTnbN6gMT7eAC8ERyksRoSjn8ulcn+lm9BEXkNQRFsJ2Dxm9+YLP8N6+EGmh1M5dnM9L/6cuQUnFAtm2cB3BopudozRS2SdnuWt7CyonKI4bIrNiC+vYFPKlhz5d5rKzSw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; 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=6JWgc0q+12jv5kIAv32LIGY1YmVkec7CyzTR2C4Uiww=; b=v8ITyOfPqPPRpPbroVLIZ7h1mKvepjv9kKDxObeBnqnqP/LA9L1QJUY4tRna0qb2dhcAoFbRKqrMVXam5xCG6aUxvaNN1cJCxZ0HyLD20Nfxs8J0eSBFXheaP2Qw9uxD+tXs6OHHzwYtXl0EMiKArzySarPYVBTA4V0mG0mgW/qoiBiBOkfMkjsNvXE4Vu89MRJtMK328C7n1StcKH56a50yZZd2+172ZkPe3/JAhUKGKGxBNE92VoaVQp/k0xryQEoyYjD8SyITLIq4h00HMZsojNu26zkptt3BzneawKNQfhIE6IQdDW970v2pBMV6nHJATT3yTj5CmSYipH3t+A== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; 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=6JWgc0q+12jv5kIAv32LIGY1YmVkec7CyzTR2C4Uiww=; b=D1rBB3ggJiSYfIrSwUwUiQBSGXKNiDSNqdbUAp6Mfgsl8JOcrC4Z7s+sl7TdyjY8jiB0230W2AFgUML5z5JxEdBzDIzUmPi8xLsUemyG6WfDdiMOXJ0YyXlwufOOoqHt1D3dVV1JyWR6yvKzt6rLDek5tFOHJaRcCf1owkTLfxpk9g73MHICgef6YSUVnMd9yf4XXR1smCUV2RrzBgRm2Jq1+JZhMRmguXM5wF012cZWaSmZbScTSVA6yhilCeo9nPP9bWFJ2YVQC6RFWHoIOibBFH8evAkNt8Jbag96A3sO2f0B2V0hGICTw5Rn6vzT5pGVHmmt+MSPni0amHl9Aw== Received: from CHBPR12MB731189.namprd12.prod.outlook.com (2603:10b6:610:33d::12) by DS7PR12MB8252.namprd12.prod.outlook.com (2603:10b6:8:ee::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.406.9; Fri, 11 Sep 2026 14:30:56 +0000 Received: from CHBPR12MB731189.namprd12.prod.outlook.com ([fe80::b0e5:123d:fe06:e10d]) by CHBPR12MB731189.namprd12.prod.outlook.com ([fe80::b0e5:123d:fe06:e10d%6]) with mapi id 15.21.0406.007; Fri, 11 Sep 2026 14:30:56 +0000 Date: Fri, 11 Sep 2026 11:30:55 -0300 From: Jason Gunthorpe To: Sean Christopherson Cc: David Matlack , Logan Odell , arnd@arndb.de, pasha.tatashin@soleen.com, rppt@kernel.org, pratyush@kernel.org, graf@amazon.com, akpm@linux-foundation.org, pbonzini@redhat.com, maz@kernel.org, oupton@kernel.org, bhelgaas@google.com, alex@shazbot.org, kevin.tian@intel.com, dwmw2@infradead.org, baolu.lu@linux.intel.com, joro@8bytes.org, will@kernel.org, robin.murphy@arm.com, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-pci@vger.kernel.org, iommu@lists.linux.dev Subject: Re: [RFC PATCH 0/3] liveupdate: Move to feature flags for LUO and memfd ABI compatibility Message-ID: <20260911143055.GI3968357@nvidia.com> References: <20260905012403.GX4157646@nvidia.com> <20260910143448.GD3968357@nvidia.com> <20260910171210.GF3968357@nvidia.com> <20260910221832.GH3968357@nvidia.com> <20260910225728.GB857650@nvidia.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: YT4PR01CA0209.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:ad::6) To CHBPR12MB731189.namprd12.prod.outlook.com (2603:10b6:610:33d::12) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CHBPR12MB731189:EE_|DS7PR12MB8252:EE_ X-MS-Office365-Filtering-Correlation-Id: a6b36284-652c-4b5a-e818-08df10114ac4 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|7416014|376014|1800799024|23010399003|10067099003|18002099003|22082099003|56012099006|4143699003|11063799006; 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:CHBPR12MB731189.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(366016)(7416014)(376014)(1800799024)(23010399003)(10067099003)(18002099003)(22082099003)(56012099006)(4143699003)(11063799006);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?ghB2DcEsdWgi62cVM61E9/HCSdw1IZLsmUrF8vvQo8mSPNVs9tjTqbxYY4XP?= =?us-ascii?Q?VFI3YjSpwQGKVN7itFHcnQjFmiHcdKp/GRrkL4A/uK/VBrQg3sc2EBIDW8qV?= =?us-ascii?Q?J6NYE0/vDdvczHaBraxmXICk0/eX+Sycjkn6dWpekYklN4+WUhRPoFdhCVUO?= =?us-ascii?Q?+reoDNZCfzCsUxHtF2X91YskRAFVcvcN5roaUXZYPaG9RPmXaomauGQgPNXs?= =?us-ascii?Q?JZVPsist2AE6oCXx6OkM/764f+zEPPPWD6X5PURagxPT85eDEXlx3FwdKyQ+?= =?us-ascii?Q?sBBxFnyWvxwNSbx3F/jAd7/M81lBF3Lbvxtb25b6ra3oaNClJQmxYjoUPDbh?= =?us-ascii?Q?B+g2ru9uTy34dahO2DoEuO8BNU/P4PiOQ22zIZzP6BfeWVtrDSwSV38waXb8?= =?us-ascii?Q?fNbh+xWX1UJ1ERJradrhGmGst4mZWyzV6XUmysU+xPJjgiBROAf67n2Gv31E?= =?us-ascii?Q?10+pl/WYLU6r6ydm5ymd8MGq1IwedO4i77ivihcgxeJJEgvNWPJ371Xd3Dln?= =?us-ascii?Q?xtABfJ8USf8C1/YDOUPwWucArc6uEyMvbF4TjGen//bv+JfNlsyUXfrZ95Ne?= =?us-ascii?Q?S/YwX4Q+uWITjM7jmtUEtEsmoBKCmWGeaNL/ZErtFwzSwY/dZQda9EbAg/sd?= =?us-ascii?Q?0+sdhWZ4Cne6NcdjsLixnEKUNqpNALIrcV/5CJc7mlXorptfuCxWhNaBeh5L?= =?us-ascii?Q?ZMkhBRiP+Xe+PGffgoAcvRjCWQq650TNbgYEjrVRyhtFxvRzLMA+rPUJ6dKL?= =?us-ascii?Q?M25uBDpJnwatwxt9T6gbPT/DPKnDg5oQVmTeA6L/DSMj0+qnVOlToEWO1UHp?= =?us-ascii?Q?88fdz5s166tEm6ckyKmfrikSaom6NsZsjjfcAZBg33QhIv4Ll5as7kyf4E7X?= =?us-ascii?Q?mvKnwSWNEZCRoCLBoerJJbpxjd/OvrHvP2oFcNBuy+Lzy/CPPLK52wzILGD9?= =?us-ascii?Q?YLp7w586tOPux7TqBWteTsqr8fokN0hAFtsJWyNGb9aeIk26pyiIhPxBXFrk?= =?us-ascii?Q?HI2RBhSvV6B9i8xUGTw29+FE6kqSV8mmBEmgy/3GwOxFV5f9jmqK0aNRRIWF?= =?us-ascii?Q?yFrBAy6uvtW/jt89xHVOAmoT/skHAuBBCQ/VvZGYTCM0o/6vXvhsGmoNURaS?= =?us-ascii?Q?4/mlpNETDtZeYinnj7ZrKhpbSsytxxoJUqgLb/yXjNSgMmTIAYF8HeMuGlwI?= =?us-ascii?Q?p2Cfwu6NXmg8I6T+lRb7nVMBRfIJvRNKQosQULqS0rxnY8FinrwFPsOxxeWJ?= =?us-ascii?Q?+MMaSLIPdbgp6UJ1dHcbQWvzNv1rgxLH2IPsUvOBApIuA3hIbAT3wuwfYWja?= =?us-ascii?Q?Sm+O4nC76wV2azqgTikZtGz/S8CXU7TR3SIkqqQCwicRDwjMWYML5lI1f5Tf?= =?us-ascii?Q?mYwuVBBlUSL5OtTTJ+pVekR68FgBQwRLLMwvH0HRLL0hwb4lyQ+Mnwn2lpm9?= =?us-ascii?Q?x/TyXt98o6uhIskuUfsowxyBKbpFC2tL6bj0aYRMGvxastydhCJXj5RwMhpS?= =?us-ascii?Q?1t8tS/ncXwVldlJKNERbAfKtkqOFbwoBhJ2o61mxgpjmk497R0k+WzUUFVqV?= =?us-ascii?Q?cmWYzQUgTVgo4wfvOWBtvxLtlL6rwp60q12Ifh/JAhvRhVtABKPJqwCxC2xd?= =?us-ascii?Q?Y1ZR6U22XEqFH/BHUGtTtsh4whUIMIm0ZGVL7kihMiU2tTROuJtQOjwoe8oY?= =?us-ascii?Q?UgMu2qwgq3SggZlyFY+GcHk+Wo2xnu51BPUPjT6j4Um/YwQG?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: a6b36284-652c-4b5a-e818-08df10114ac4 X-MS-Exchange-CrossTenant-AuthSource: CHBPR12MB731189.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 Sep 2026 14:30:56.5809 (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: fepAJgBwHzlnlaplDdx21RzSTHuRRaAOoEUjIOR801XfaDEqdtz6pCjdlrZMAWCB X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR12MB8252 X-Stat-Signature: q67smuq5hehm54gft41zkobub7xn8phs X-Rspam-User: X-Rspamd-Queue-Id: 48463C0009 X-Rspamd-Server: rspam03 X-HE-Tag: 1789137068-112978 X-HE-Meta: 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 HYi3fsSH Zi2FA27E6l14o8+YdqzCLsxGA1H+qrswdmrSvRqu6WldUAi4etRUnyUFYterPSZzqdzUb5sCADmBWUg/bwgoTyQEMXMBoo4B4xlbbovA1c8UxMLq+vonwmOJxusIlQeT8wQ4rZPKj66QEyiVOx3+CSkgj/IUfs8VV7f9velF72e2hmCSvzOrzLMSQG7+CxcbCNrmblXnTagEvsFlo0Z91nrl/jjlXVX1O8k6gbUYmTPqjXNl7wgezZtUtJJX6XT24NJdOjBcx7UZ/9pEWgY9ngK5ZGEim7j2GzegHr/dcGef+0Oq+wZygCVH3WFEy14mvZVemcD/9nZUaLGRPlbzg38FaAjJb1pYpuVnMU1AfNxtCk7jFSov4atMTtqf1WnXy0mddSeWmLAC64s47P2QAANQYnQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Sep 11, 2026 at 06:44:50AM -0700, Sean Christopherson wrote: > On Thu, Sep 10, 2026, Jason Gunthorpe wrote: > > On Thu, Sep 10, 2026 at 03:42:36PM -0700, Sean Christopherson wrote: > > > On Thu, Sep 10, 2026, Jason Gunthorpe wrote: > > > > Sean's initial email was asking for strict never-break ABI compatability > > > > rules on top, and that is what I've been reacting to. > > > > > > No, I was never asking for that. I think we just have a different interpretation > > > of ABI, or rather are talking about different pieces of ABI. > > > > > > I am still asking for never-break serialization format compatibility, i.e. the > > > more literal save/restore ABI. I'm not asking for full backwards/forwards > > > compatibility across all kernels version, i.e. the higher level "kernel" ABI. > > > > > > To phrase things differently: I am a-ok if kernels are inherently incompatible > > > because they fundamentally operate differently and/or support different features. > > > I am not ok if we end up with incompatible kernels because the save/restore > > > interfaces and payloads are poorly designed, lack abstraction, etc. > > > > I can more agree with this, it is mostly what I thought we'd end up > > doing anyhow with version numbers and growing the structs not > > replacing them. > > > > So you still end up with a version label (string I guess?) because we > > can break it from time to time, > > Why bother with a label/string? I don't understand what it buys us; I see only > pain. Make the features discoverable and punt on all of the "is this pile of > insanity my company has created compatible with this other pile of insanity?" to > layers above the kernel. It is one layer above, the serialization ends up with 10 memfds a couple iommus, kvm, pci device, etc, etch. Each one starts with a string label saying what it even is - to dispatch it to the proper de-serialization code, then some detail about where it is (eg a handle to recover a FD later) and then the actual object serialization data itself. So the features are fine to handle the ABI within the object and a memfd-v1, memfd-v2 is fine to handle labeling the object within the stream and gives us an option to reboot the ABI if some reason comes up someday. If features are a perfect success then we will never need to go beyond memfd-v1. I'm just saying we should have the option and plan for it. Jason