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Mon, 5 May 2025 10:21:38 -0700 Received: from nvidia.com (10.127.8.13) by mail.nvidia.com (10.129.68.6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.14 via Frontend Transport; Mon, 5 May 2025 10:21:12 -0700 Date: Mon, 5 May 2025 10:21:03 -0700 From: Nicolin Chen To: Jason Gunthorpe CC: Baolu Lu , , , , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v2 13/22] iommufd: Add mmap interface Message-ID: References: <7be26560c604b0cbc2fd218997b97a47e4ed11ff.1745646960.git.nicolinc@nvidia.com> <20250505165019.GM2260709@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20250505165019.GM2260709@nvidia.com> X-NV-OnPremToCloud: AnonymousSubmission X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS1PEPF00017092:EE_|SA3PR12MB7921:EE_ X-MS-Office365-Filtering-Correlation-Id: f5a41d27-57e2-4798-1c04-08dd8bf955f3 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700013|1800799024|82310400026|7416014|376014; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 May 2025 17:21:56.0304 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: f5a41d27-57e2-4798-1c04-08dd8bf955f3 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.232];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: DS1PEPF00017092.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA3PR12MB7921 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250505_102209_139715_D7259ED8 X-CRM114-Status: GOOD ( 20.32 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, May 05, 2025 at 01:50:19PM -0300, Jason Gunthorpe wrote: > On Mon, Apr 28, 2025 at 10:50:32AM +0800, Baolu Lu wrote: > > On 4/26/25 13:58, Nicolin Chen wrote: > > > +/* Entry for iommufd_ctx::mt_mmap */ > > > +struct iommufd_mmap { > > > + unsigned long pfn_start; > > > + unsigned long pfn_end; > > > +}; > > > > This structure is introduced to represent a mappable/mapped region, > > right? It would be better to add comments specifying whether the start > > and end are inclusive or exclusive. > > start/end are supposed to be non-inclusive range in iommufd > land. start/last for inclusive. > > This should be a u64 too Will fix. > > > +void iommufd_ctx_free_mmap(struct iommufd_ctx *ictx, unsigned long immap_id) > > > +{ > > > + kfree(mtree_erase(&ictx->mt_mmap, immap_id >> PAGE_SHIFT)); > > > > MMIO lifecycle question: what happens if a region is removed from the > > maple tree (and is therefore no longer mappable), but is still mapped > > and in use by userspace? > > I think we should probably zap it and make any existing VMAs > SIGBUS... Otherwise it is hard to reason about from the kernel side I added in v3 a pair of open/close op that would refcount the vIOMMU object (owner of the mmap region). This would EBUSY the vIOMMU destroy ioctl that would call this function. Thanks Nicolin