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Mon, 5 Aug 2024 20:55:41 -0700 Date: Mon, 5 Aug 2024 20:55:40 -0700 From: Nicolin Chen To: "Tian, Kevin" CC: "jgg@nvidia.com" , "Liu, Yi L" , "iommu@lists.linux.dev" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] iommufd/device: Enforce reserved IOVA also when attached to hwpt_nested Message-ID: References: <20240802053458.2754673-1-nicolinc@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1PEPF000075F1:EE_|LV2PR12MB5750:EE_ X-MS-Office365-Filtering-Correlation-Id: fe8bfdca-84f1-49ea-9094-08dcb5cbab2a X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700013|1800799024|376014|82310400026; X-Microsoft-Antispam-Message-Info: =?utf-8?B?UzE1ZUhFNWQrNXZ5cllVeERxdmRqcVMvWEwvS0QwbzhNK1RTcFkzVng0cC81?= =?utf-8?B?ZG11TTFTMFNXeitIS2c2MUNVSk1IZkROcHE3a1VYTEpiTlFwLy8zRVhGbXVG?= =?utf-8?B?Z1ZielJnbS9OMSsyTHZ0TWtsZFNvTWQrbng4V0RaSVhKMzMyNEx2VllwTUlx?= =?utf-8?B?eWVMWFBnZEtUTjVCT1l5NlBEcFV5WWh5YlBuUVg1TFhlRmFVL0VoNXlPMDZN?= =?utf-8?B?dXcyYTBwTzlvSVpHc1ZwOU1Qb1dDUmF4ZUpqczB4QVFpOXZrN2NwZjVnMlY4?= =?utf-8?B?UHNYNTNWUWI1NExlVXdORnBSTlBNY3cwbSt6aEl3amJkSi82Y2o0ZEdNMVpv?= =?utf-8?B?SjY2aERYNnowNzVKT2xOV1NUeDVONjhMTXk0WVVXWGhwMkx4OXVYUGZjR3pz?= =?utf-8?B?aHYwcWdtQkFUOUZrSlF6djVWblVJRE1QNU9FWC9CcWcvcjZDTkp2OGdaeVVw?= =?utf-8?B?MVJJVDVxdDF3WVZuNmllaFk0eWx6RVVURkgyM2M4b0ovZWlvK0YvM1FBNGt5?= =?utf-8?B?UUtYaXFHU3ljQVNpd2p1bWFzeE9DcWRYVjBmOHNQVmpCNElTb2QyaHhOS1RP?= =?utf-8?B?d1NHVGxzcU53VDE0SXB5dnJzVHFtYkp1TmxPRm01aWFkMXJYT1lCT1B1M2lV?= =?utf-8?B?TUdoL05mL3ZlREREVjYvRDFxWi9ZUGVXQnR3blBTdXprWFZLK0tmTk44TTNu?= =?utf-8?B?OUlnc0luYWxNMDFVSFVaMWhqNURpWGRsZUx1SHkreWZKVisxVG1SV0JaUVJ3?= =?utf-8?B?cFVzMmg5VjdnOXYvK3FNVDlTWWNzM1pvYjNRK095OEhLYmVLMUVjWEdDVjNN?= =?utf-8?B?MlVsQWl2dVpxbXFSQ09vYjZQZzFXUEorM25Sb1JFb3FsbFJaV05NSGVWTStM?= =?utf-8?B?b3ludnkzVWdROEhjUzNya1VmUjhxLzRsaGIzb0VndnNmQlV4Tm9HWDBkNzdr?= =?utf-8?B?aTdhNjFBSHFidVdGRXlHdTNkVmdNR1k4UEZBTmhHSGhXcTY3OUpxN1BvL3Rj?= =?utf-8?B?T3Y1OU1HVUJMNkhaU3BGaFVuOUR3MUF1RzBQVkhyTi9aMmcrV1MvMVV3RGM4?= =?utf-8?B?REJEb1RtZUIzY1VVT0FPNVE0ZEEzMTFDTkpkV1FUYXBvMTR4TmNzanpuT0ky?= =?utf-8?B?WjNKdDVTNW4wd24rWlVtRlJwQVJRSXYwYmF5Tmw4OTkxNDhDOEwwcjBta0JD?= =?utf-8?B?YUtzbzdaNFRKd1RLYzd4Q25xVHVrNmNGWEkrUFFZK0VHSElSYTcvQXZoTksy?= =?utf-8?B?R1FUQVYvNXp4Q0RFV1F6NCtVdURDNCtJUi9LNjJQZDR5SjR0bVRKOGU3bXhX?= =?utf-8?B?WFF0NzlpWjUvODk1Z0N0TXAyUHA5K3k4WjRFblhwKzhDVlFBSmdxQ3MwSSts?= =?utf-8?B?NlRPRlpucllZdHUxYXU0azhrNVAvZ1NZTGMvVTl5SjJZL3VOeEhXSW5nTUtz?= =?utf-8?B?RW5aQW1OQUovWEs0UDA3YU5TWkNCeFJnU3NPRTl0TXV5VDhvM05xUmUraEpE?= =?utf-8?B?VGhjN2g0bFBUL05QcjRqc2xnOXF3N1J1eDhUKzdxWkpRNHJsS3U0M1ZxWWEy?= =?utf-8?B?dWJBdkMxdWxvYmZ2c2pTQnhhdlJpQzY1b3hOOWpabklFMTZoUDBNaGlZNEc1?= =?utf-8?B?SzVOZnB6SXNNVnpvRWJtcmVZcU1tMUpVRjJhenJmRFhpTSsydVh4QXpkVmZU?= =?utf-8?B?aE5lWUtDdUw5VTA3d0IwRGZDMFh6Mm51K05CejcxMWpETmlWZld1TytNdkZU?= =?utf-8?B?ZnVoTzAyWFkzM3JOcFJTNkdPVEpiVGJxRUJSblVkSXk3ekIrTkM3OVhiWnpx?= =?utf-8?B?Y1k3czVXNlE2T2pLVXN5eEpYUFdvQndQK3l6R1hmR3liVnpVeWRSc3JyQ3lB?= =?utf-8?B?V3J4bDNJdHI1RElwcUpzWGZ1bmYyd0JoWlNFNTJvSlBjeHdvZkRGMFpYcXhp?= =?utf-8?Q?Iel9zBo4ZDFI8BFfB1vcP/69286bRjKB?= X-Forefront-Antispam-Report: CIP:216.228.117.160;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge1.nvidia.com;CAT:NONE;SFS:(13230040)(36860700013)(1800799024)(376014)(82310400026);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Aug 2024 03:55:53.3668 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: fe8bfdca-84f1-49ea-9094-08dcb5cbab2a X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CO1PEPF000075F1.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV2PR12MB5750 On Tue, Aug 06, 2024 at 02:59:53AM +0000, Tian, Kevin wrote: > > From: Nicolin Chen > > Sent: Tuesday, August 6, 2024 2:04 AM > > > > On Mon, Aug 05, 2024 at 07:40:45AM +0000, Tian, Kevin wrote: > > > > From: Nicolin Chen > > > > Sent: Friday, August 2, 2024 1:35 PM > > > > > > > > static int > > > > -iommufd_group_do_replace_paging(struct iommufd_group *igroup, > > > > - struct iommufd_hwpt_paging *hwpt_paging) > > > > +iommufd_group_do_replace_reserved_iova(struct iommufd_group > > *igroup, > > > > + struct iommufd_hw_pagetable *hwpt) > > > > { > > > > + struct iommufd_hwpt_paging *hwpt_paging = > > > > to_hwpt_paging(hwpt); > > > > struct iommufd_hw_pagetable *old_hwpt = igroup->hwpt; > > > > struct iommufd_device *cur; > > > > int rc; > > > > > > > > lockdep_assert_held(&igroup->lock); > > > > > > > > - if (!hwpt_is_paging(old_hwpt) || > > > > - hwpt_paging->ioas != to_hwpt_paging(old_hwpt)->ioas) { > > > > + if (!hwpt_paging) > > > > + return 0; > > > > + > > > > + if (iommufd_hw_pagetable_compare_ioas(old_hwpt, hwpt)) { > > > > > > hmm this change is broken. In this helper: > > > > > > if (!old_hwpt_paging || !new_hwpt_paging) > > > return false; > > > return old_hwpt_paging->ioas != new_hwpt_paging->ioas; > > > > > > Obviously the original code wants to enforce reserved regions if > > > new_hwpt is paging && old_hwpt is not paging, but this change > > > skips this scenario. > > > > Hmm..I think that is the intention of this patch? > > > > The original code does that because it didn't enforce reserved > > region (to the parent paging hwpt) when attaching the group to > > a nested one. Now, it does. So, we basically check whether the > > associated ioas has changed or not. Right? > > > > that is too much tied to nested vs. paging type. In case a new > type comes w/o parent/ioas in the future, above will be broken. > > IMHO to_hwpt_paging() already resolves the problem about > nested parent while the original code above appears to be > more future proof (w/ the enhanced to_hwpt_paging()), i.e. > adding reserved region to the new hwpt w/ ioas as long as > old/new hwpts don't belong to a same ioas (including the case > where old has no ioas), instead of adding reserved region > only when both old/new have an ioas but different. 😊 Ah, I see your point. It failed to cover the case where one of the hwpts returns NULL from to_hwpt_paging(). Will fix and respin. Thanks Nicolin