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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 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