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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?E2IW7ZGfWs1ZUXsay20J9Ft2pgEM7eymLwq/KtylgbZ8fSoIWCJq/DbLpDUi?= =?us-ascii?Q?ySmUNPh6Xg0Fx0aHB9mC9nphYiry3zQHX7n0e5vptk8S++6HaYAKcecKn+27?= =?us-ascii?Q?PkxaWXCHGGoRGpH6WSWbbC6jqjJx87hBDz2tkEu0U0+Ki7AyosQ9WHRVNwQM?= =?us-ascii?Q?HSaJfDjrXoXiYzykAP3jriKSbHg+yin3wrxGXLGyGxD5JG0G9yZF7SkUm7TT?= =?us-ascii?Q?1IJEIL3aGdHSMtMoq7tzy6p5uIjRDGVHizYpI8d8MEdPcVx+tmceHtWiSbbE?= =?us-ascii?Q?b8x+jjsBbAewarujvtXdBjHfXu+NxQiAtOcAEmn2oCUvu0bEsj5qG4MwQCsf?= =?us-ascii?Q?I756SAx2Yj/4X8T8KfZMwKOINEXO2nWWFNo7QwLz/BJ8Is88lX3rzVwLf6f+?= =?us-ascii?Q?/lxY9QwbSjfurUHn6oUWDs4BvHvzTrOElVVZ/ySs/MUGmLMGy/mxAIIJVX8Y?= =?us-ascii?Q?yRm7MBWjkFCtdJQd8TJO1i+AnYosIcNWxRA7X8dvXFpWYfwPj5K20AYUclNN?= =?us-ascii?Q?hgkBL24r5Rbga3Qyfow6tZjB+SzXyp8W61YsJ1N8keXTVdINnXPDhklB6GLJ?= =?us-ascii?Q?4d0Ua7OHBVMZTs4J/uzun2/gGA9UQ7kYAQLVrfWY2IO3kHZqz9FmDhp5tnwz?= =?us-ascii?Q?vwcfjnPRiSoOB1In/4LRJEevz4RdEwaVBAMwz4ln5AmDPzapqJrU+7FLPfy1?= =?us-ascii?Q?DZxX8UwE/potjbmSYvpiE1FmLfrDk8MzR34PHgYOn+wI+UanIR7m6lhAZ2VT?= =?us-ascii?Q?IDw1+jU3MBCCaxpieSZKqn79HxChNKpIgYa0e9hC6VFGRtxQUicx2XNPN/BC?= =?us-ascii?Q?lyiZOCmGh5wPKnK4fJBKaJiVTzPkO/1KN3RUmNVYkOnjdgjGU0O7NpXMCjLa?= =?us-ascii?Q?8E2HUw+0U/zPOWzexGErTEHwcKHBY2L+AZxjncoT0GQptDxlkuC5UfwC7cP3?= =?us-ascii?Q?13QczhLmbpfiBB6LO7ZpzW+D8Sb1bRFS2JxQna6/gEZ81PC2Cg4N82KxoZUe?= =?us-ascii?Q?YAuxLBxzHv7p2Wdrm/l+HgHMhbQSa27jjHKyiYh0eHx7Eg3Vv+peeNX8X9qL?= =?us-ascii?Q?fgIHhNvbm1Du71jyvBPGicHKAmlLVXlWJyWOH3SQGGJw8ivcuUGos3FjzNzh?= =?us-ascii?Q?/j8H6lOIoZ+gheAaZXeEvSxu6snuDJcy/qeo2wntCx5ur90I5rIFPAzXRtve?= =?us-ascii?Q?fHsrOfbNcYfwIT+EhjjaiLb6K4pjHgqnYz0V6nqvcyIw7uIbs0Kkw/hdfyft?= =?us-ascii?Q?0JA0aefuRSb45HACdZjD7tcp/VVHt2KQh9j13iT/DIFw+s8yu7fUq3CVcRbT?= =?us-ascii?Q?RJCdunFGY1UWYMr5rJL1JyeBa6Y/SnRDAEsvSvbghOpgE22F+kh/wa8nbMcq?= =?us-ascii?Q?YhvAvcbu8+0bZkw5HDy0Gi+Oth4bznFNT9NRXv+PYngZ//HritWsnwJnKyu1?= =?us-ascii?Q?sZxJv75z7QkYzwhctHM9SQCtoarJMyw6glgRpNSaH02vP3g2zsPIt/Vt6NU/?= =?us-ascii?Q?oahKHXItGOcxt2jU8UnbLTVBFU0UOP5hSWl925aTYm+nqmSOrH5lrMSyFdG9?= =?us-ascii?Q?lQSkmLS2LJ0/ep16pb1gT1/TGfIEeB2lBBFh7erm?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 102ae539-15e0-4178-ad62-08da716c45d9 X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB4192.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Jul 2022 14:11:46.9900 (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: QpcJK3lt5j+iY4nSv0OIYoSoK6t2l6KC+n+cDz5DTfXZhlV0utFQR4MJTb1z4BHa X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB5199 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Jul 29, 2022 at 03:01:51AM +0000, Tian, Kevin wrote: > > From: Jason Gunthorpe > > Sent: Thursday, July 28, 2022 8:06 PM > > > > On Thu, Jul 28, 2022 at 04:05:04AM +0000, Tian, Kevin wrote: > > > > > > I think this is not correct, just because we made it discoverable does > > > > not absolve the kernel of compatibility. If we change the limit, eg to > > > > 1, and a real userspace stops working then we still broke userspace. > > > > > > iiuc Alex's suggestion doesn't conflict with the 'try and fail' model. > > > By using the reserved field of vfio_device_feature_dma_logging_control > > > to return the limit of the specified page_size from a given tracker, > > > the user can quickly retry and adapt to that limit if workable. > > > > Again, no it can't. The marshalling limit is not the device limit and > > it will still potentially fail. Userspace does not gain much > > additional API certainty by knowing this internal limit. > > Why cannot the tracker return device limit here? Because it is "complicated". mlx5 doesn't really have a limit in simple terms of the number of ranges - it has other limits based on total span and page size. Jason