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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?n9JH8NHwXVqgiVbof3qoRgpO8tX4koSDlcrlzAIFNJdqd3QqYOH501oRG9lA?= =?us-ascii?Q?BS+IH/6ZQdh4uRfmF4wSP65UzMFVe96vRNj3HhsMi0WVXIyTqPPKI/9gEyaf?= =?us-ascii?Q?3riulgzyoIpqjj0y8BVw05IOf8GnGabFrO6pmGizckU/msxWNVte9+ChhOyD?= =?us-ascii?Q?BtD7sO1uNsBJGblVzxoqz05rw9ZjIq/MKW63KxRfiim/uZNu9CTFqY7JHKvq?= =?us-ascii?Q?ayWRA/703VB85PveReO6M1CJP949xXm47puNk66SkexmhipY6a7WXzBFpU+d?= =?us-ascii?Q?YaByDuwD7vGtU4xDGjJXjOxk6Sp50ONdvIzN4GldyE3CbyTAThgPatb32fXq?= =?us-ascii?Q?09neXxO+kjqJ8Yd0fdJUqUhjS90CJ0l0WC8aW2x30eya+4iXuW7AIf6ZCDb3?= =?us-ascii?Q?OgVfxHtv1h0Cxus26Yv+ul9EFIgVNWNVonteKgTWaW/SPkh3h0wcspjDvLJO?= =?us-ascii?Q?x5eP5AiIG3Soct8kSL2Smso2bz2lV16SeeRwaqwdNKBprn9KV0XNcAU+C2w4?= =?us-ascii?Q?cpNjq/mbujmXXg7m7kj5WI8uZH8Tb7OO7SGYd24qxzuXmJjww3eBqLd7gjBk?= =?us-ascii?Q?J8yqyTqDxI1PHMkRPNxrSLJbKRTD/eUNs01Wurtd1Zml8VER+vmafYmIVPJX?= =?us-ascii?Q?vv2mgtMnoUdYgfm+XFu8s8hPNz4JGReCk3Uj84pAAWIS7cOyX/PELh0HmZv7?= =?us-ascii?Q?UqoHsC804fNH9IGX+jNU7n12Cr5cFHxMtHQltG+KWlNKna+/Sa5kNuulucSh?= =?us-ascii?Q?tkgV83NN61FIUzSrfs2LM82gz70Fxqxs39Iv8q7mnTiFav+yxm+XVZbJNe7h?= =?us-ascii?Q?hhaYHXhqMrXT5Sa/AUtliV1tNrnKwwI8ZR4KhxNSkhxSwEb8iExfVvlp7uKP?= =?us-ascii?Q?5UF830WLnfJ/BXPdBM9f/Gfpaua0v2EuJnn+Ljz8uGijxGZTy+CP1AFvmOYX?= =?us-ascii?Q?dpDMUFIFKo62zZSn5G3f5DVw2YceI4Zd34khFyEfnlE7Z+oA4rG5Oucl/phM?= =?us-ascii?Q?EAEYzX9TMGA3Jr8WV7ipxShN5hWDmNOeBhzP/umlP6mwCVGd8vLJnxRV9Sxd?= =?us-ascii?Q?9ahwMK5I3gSgY+W7U/oqawml/OoAcghwo+kJR/+IFt75NMN0tTf4OHz2g6P+?= =?us-ascii?Q?xsxZy1oq/A9j+tzcDbbl1MdANWmu4QjUuvNTUW6oeRfIX5ScvcKyMvsssERA?= =?us-ascii?Q?RSc7H2JJov2Ojcnq6/5JITRiOewtO6kNICdWbjACokptIPAZ4Ro6zJSfMROu?= =?us-ascii?Q?vECuaFhiBQ/Y/YtPvQ+nDf2HFYnitWr6tRQ/9digJbTHTTIS2K3fBXZedV8Z?= =?us-ascii?Q?Ctv+CimHCnOGo5MAeJCVwiOIvWMj/CFEXoBb48WnARo7sC8JcMi9J7ao52H0?= =?us-ascii?Q?C4DG6TU5M+4TAaudZ0zb3PAGLF+qKv7AcrM0o+67/mG3CJRi1/SIjFJcsx3Y?= =?us-ascii?Q?265aNVEKsvssxnzpTDrOCQUEtyCt1XN70JOhTJ1l0qKr2g2QwIIAuE+iTe0H?= =?us-ascii?Q?t9rW5KJ60PVSPIYuqTh6cUglAFk8EsGX3wucZy2I037SLuuIb1XvDsBlyqyh?= =?us-ascii?Q?TZWyOhV9WAKGbxBm9WB2OEn9M5luh8yPQKfLNRe+eSPRKfhi5R3lHMkM7Fj1?= =?us-ascii?Q?Tl6P2DPT09D2n62XlwWqcqVLkRnpcJ+0VnbGmS9k982LNIiOv9Oh+xYckeU5?= =?us-ascii?Q?pRjz354Y8zqDCEym5X6vT28pYcdLEUzy/z51rrmeBao8rb2I?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 789cbe2e-7e9c-4a15-72ea-08df2094986f X-MS-Exchange-CrossTenant-AuthSource: CHBPR12MB731189.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 Oct 2026 14:51:09.6676 (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: 6oLkrp3FNsawpPVnYcePwFEU4h4ZeAwK7OIKRBfd2HkP8voLl9iQzFWBjqsjBZIM X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB7744 On Thu, Oct 01, 2026 at 03:38:34PM -0600, Alex Williamson wrote: > On Thu, 24 Sep 2026 16:21:43 +0100 > Matt Evans wrote: > > Dear Reviewers, > > =============== > > > > Along the way several related issues came up that warrant more > > eyes, and I'd be grateful for your input: > > > > 1. If VFIO fd is opened O_RDONLY, it currently can't be mmap()ed > > (because PROT_WRITE is rejected in do_mmap(), and PROT_READ alone > > drops the VM_SHARED so VFIO's mmap rejects it). BUT it seems we > > can export a DMABUF from it, and then pass the resulting fd around > > for P2P writes. > > > > I don't know if this is intentional/relied on/a known limitation, > > or a bug? > > Seems like a bug. In practice it's probably not very meaningful, the > user can still potentially change the device power state and trigger a > reset, but being able to source a writable dmabuf to a region on the > device fd that isn't itself writable seems semantically wrong. I'm shocked O_RDONLY even did *anything*, I never expected this. IMHO with these kinds of cdev's we shouldn't do anything in response to O_RDONLY. If the core code does something then fine, but I don't think we should try to define a semantic what "Read only vfio" even should mean. > > a) We could reject export w/ -EPERM unless the device fd's f_mode > > has O_RDWR, to reflect the RW abilities of P2P > > This seems sufficient... +1 Jason