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Received: from MN2PR12MB4192.namprd12.prod.outlook.com (2603:10b6:208:1d5::15) by DS7PR12MB5982.namprd12.prod.outlook.com (2603:10b6:8:7d::12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5612.12; Thu, 8 Sep 2022 12:08:40 +0000 Received: from MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::462:7fe:f04f:d0d5]) by MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::462:7fe:f04f:d0d5%7]) with mapi id 15.20.5612.019; Thu, 8 Sep 2022 12:08:40 +0000 Date: Thu, 8 Sep 2022 09:08:38 -0300 From: Jason Gunthorpe To: "Tian, Kevin" Cc: Robin Murphy , Joerg Roedel , Nicolin Chen , "will@kernel.org" , "alex.williamson@redhat.com" , "suravee.suthikulpanit@amd.com" , "marcan@marcan.st" , "sven@svenpeter.dev" , "alyssa@rosenzweig.io" , "robdclark@gmail.com" , "dwmw2@infradead.org" , "baolu.lu@linux.intel.com" , "mjrosato@linux.ibm.com" , "gerald.schaefer@linux.ibm.com" , "orsonzhai@gmail.com" , "baolin.wang@linux.alibaba.com" , "zhang.lyra@gmail.com" , "thierry.reding@gmail.com" , "vdumpa@nvidia.com" , "jonathanh@nvidia.com" , "jean-philippe@linaro.org" , "cohuck@redhat.com" , "tglx@linutronix.de" , "shameerali.kolothum.thodi@huawei.com" , "thunder.leizhen@huawei.com" , "christophe.jaillet@wanadoo.fr" , "yangyingliang@huawei.com" , "jon@solid-run.com" , "iommu@lists.linux.dev" , "linux-kernel@vger.kernel.org" , "asahi@lists.linux.dev" , "linux-arm-kernel@lists.infradead.org" , "linux-arm-msm@vger.kernel.org" , "linux-s390@vger.kernel.org" , "linux-tegra@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , "kvm@vger.kernel.org" Subject: Re: [PATCH v6 1/5] iommu: Return -EMEDIUMTYPE for incompatible domain and device/group Message-ID: References: <20220815181437.28127-1-nicolinc@nvidia.com> <20220815181437.28127-2-nicolinc@nvidia.com> <9f91f187-2767-13f9-68a2-a5458b888f00@arm.com> <0b466705-3a17-1bbc-7ef2-5adadc22d1ae@arm.com> Content-Type: text/plain; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?YC7ZpSaWO3c6nwIXl1I1baJNiCGDp9UeVFhiHmN4pffm1XvGbAMq9eu2remb?= =?us-ascii?Q?QCmBpmNYiE0QHW64d90+q1bEXSbztkgAcXn1nky6MmrrROUhTA/SzVfCxZad?= =?us-ascii?Q?SQ0wJGNH+xBWDD4RVN5BhYXzk9G+FnXhx+ULoeZDKAkYof1ILmmdhvca4pqu?= =?us-ascii?Q?t5F19JA4jM1Sxna+5wyA2IFCETjxy10k7P6bQHjayTm2DGve5Ib8YtdLn46/?= =?us-ascii?Q?bYufWsXV7KpeoyqMjfErnM55mMTJYY9eXBIdVDh4Y9LZ8DXNE9iTYtg0dAnU?= =?us-ascii?Q?kSm011HNwk2CGU8BBVrOyJAo+QzvFQ0pl1ROZ7g5m7lY4UeHkVIKjgub5xg9?= =?us-ascii?Q?jL3/H8Smpx4diwMHBcSIH6tTAqx5fgb9K8APbq8DzsCDDMhenJAymAYXlXQI?= =?us-ascii?Q?XS9qb9LTairjYMV7wAsf5oIARp18fEl+z20fHl80gRcRHGfWeKC9thpsoVi/?= =?us-ascii?Q?uZeWbMXf3XvrFCvu1TPNlfBWtv1zlBrcBLyhQ4yfZpjoan4pd+EOzTAxXSYI?= =?us-ascii?Q?XTTgb/ahDlx+53WAWFNQlTLPA4759e7Gy90dqE56DpZVtnyqQO0ED/8v3QY/?= =?us-ascii?Q?LUqNVEmmJKsQzet1EPYnKeB2t1tbav2i4+Q6a7vA2nheZxy0yMkVbdXJz3rE?= =?us-ascii?Q?Umhp68l3EDDhupBHJIHgoTRhURNvWgXljlFbgZToTSb0s1hroQaPqwQz+xnm?= =?us-ascii?Q?6Gv+xc5nADe2V3H0/pjwOtcjIuOR8b5eQ2ujiAGRswAECI9YhmNRcS1qaif4?= =?us-ascii?Q?7Guoxg8Xi8ktFee2qGMxeOKm0Xp5srsxw7Lta4K3NXwlC9SBzz0bYahmzTRe?= =?us-ascii?Q?rMoMXkPXhXZOCBMJWc1b8FpfJ1518vjxRVBa3xQuzLiwn9Mvk8mebISj7OII?= =?us-ascii?Q?VqKvOXA0jhKmrLW8NY/8xYfAD1DF5jVmhzfwlbCCrTa0wswi5fOgwyxwg19d?= =?us-ascii?Q?PbacvtBy2pm+UrLVbaIj/S7mnWq+YY7oIYZZCOgiBEsjkEKhUAFoRfMtvu8a?= =?us-ascii?Q?hL/5d4LP9N0SBvrY08VVHfbG246ZuaHB/s21dCpdf/V6/ZXUWTi0A/SLB6Zd?= =?us-ascii?Q?ppYT+NxtBJnKOhRdfaeVFEO5tcOcFUI2rFRwkoOqepf7rHBNlw8GmMosXm5B?= =?us-ascii?Q?hrRy//xwT7XGXtfIPOHF6eCOHDEvIzv+RNffcYU2UsWMSvDsnwqKADeGH1uc?= =?us-ascii?Q?ZGKKPq1r64P0QhdWvo6C76Q1rKvz+/Fx8Mc2+1GwxhsLeB4m4BLRhCR+uwnx?= =?us-ascii?Q?OK5rPpsViQqyrl9k3EgqS78d6YX9HgkFFY77uaI6Il+16NIniqmo9EjjPWKM?= =?us-ascii?Q?9w4Xm6p0GcYpcH7exul/jH6IUf8ztmAbUlM0kRGND8k27u3PpilCDEFyysvp?= =?us-ascii?Q?3aG+Km2bBwENSN0w5iKEsUtb36Vz6MYeYRY8WEtvsM1+OZG0+xJPYqvyRGSQ?= =?us-ascii?Q?+LZ17IviGu8rL5pmyjmpgKtzexyUs9jwnzixV1fcvSsEfVZ54KWHuN/0meca?= =?us-ascii?Q?j/C1YrG7KXcVWEnVkk9+uDnu5HcoebbIuncavvTLUajMfzJZWPZXaW3dVABz?= =?us-ascii?Q?770ox9S8tSBKtR92m5WJpAtW/IQOdFGpuMr5lSta?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 3244c35b-ec15-478a-ddbf-08da9192dda6 X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB4192.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Sep 2022 12:08:39.9112 (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: 3tUARSHUMPfq9ikfUIzkS8+m9cKF5BR5O18RpHndTLj2Iu8lGTF+aGugMXsj1tm/ X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR12MB5982 On Thu, Sep 08, 2022 at 09:30:57AM +0000, Tian, Kevin wrote: > > But OK, I'm on board, lets use more common errnos with specific > > meaning, that can be documented in a comment someplace: > > ENOMEM - out of memory > > ENODEV - no domain can attach, device or iommu is messed up > > EINVAL - the domain is incompatible with the device > > - Same behavior as ENODEV, use is discouraged. > > There are also cases where common kAPIs are called in the attach > path which may return -EINVAL and random errno, e.g.: > > omap_iommu_attach_dev() > omap_iommu_attach() > iommu_enable() > pm_runtime_get_sync() > __pm_runtime_resume() > rpm_resume() > if (dev->power.runtime_error) { > retval = -EINVAL; > > viommu_attach_dev() > viommu_domain_finalise() > ida_alloc_range() > if ((int)min < 0) > return -ENOSPC; Yes, this is was also on my mind with choosing an unpopular return code, it has a higher chance of not coming out of some other kernel API > If we think attach_dev is a slow path and having unnecessary retries > doesn't hurt then -EINVAL sounds a simpler option. We probably can > just go using -EINVAL as retry indicator in vfio even w/o changing > iommu drivers at this point. Then improve them to use consistent > errno gradually and in a separate effort. Given Joerg's objection I think we will do EINVAL and just live with the imperfection. It is not just slow path, but being inaccurate can mean extra domains are created when they were not needed. But I think we are getting into sufficiently unlikely territory that issue can be ignored to make progress. Jason