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Mon, 5 May 2025 13:07:44 -0700 Date: Mon, 5 May 2025 13:07:34 -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> <20250505172813.GS2260709@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20250505172813.GS2260709@nvidia.com> X-NV-OnPremToCloud: AnonymousSubmission X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH2PEPF000000A0:EE_|CH3PR12MB9148:EE_ X-MS-Office365-Filtering-Correlation-Id: 4d72e028-5bc3-4427-27b9-08dd8c109b91 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|7416014|376014|36860700013|82310400026; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?+qJ91BnoVrz/HUFEM8SsSTbVUkTyTnPxZlYavrAUtvMlflA33dKFexF7rIlS?= =?us-ascii?Q?xqIC7KuaIc050VbqxfoiWQ2LgRaWCS7FLtGyh2N8U4Vu6Rfy32eLRPH4wR3S?= =?us-ascii?Q?cav2IAceYnRhYxdYBm0hW/k8QzwidSmjEfY4bjWZbbFtmAq2Rd6ugYexdts5?= =?us-ascii?Q?dbyjrSEi3hNnu8oHGJLECLnry2s6WM+E945AplMEACO8o3OmFW5Pm/W1DnYY?= =?us-ascii?Q?N/YVB/ISCPcgF05iSQsk/6UR52nDM22UKgd8pawtjTIGYSDZ8TJ4NiAK5kWV?= =?us-ascii?Q?0Gnicwy5GrmdnMrHSUwK46uaAvvB+v7ALpf8Sgy8Ii9j4GKDJpCHt6rZ+ZVR?= =?us-ascii?Q?mkEAP720C5fGj4GCgcAzVSXYQmdeaLtmnDj+OfBtqe+buGZB2u5KdjjE0Oya?= =?us-ascii?Q?SKJjkC4wGllPKkYouYk9Rmh1cNEk/h5umU/8S0OZweqDweNz0cdE/0e6b71F?= =?us-ascii?Q?WJxXgOgoKoGNWmYBf1ewrc3bsM57IM3kTMTp5xchQR4Zdhu7QpelM/R/hy/6?= =?us-ascii?Q?LSNIQYPkehvSfrLhil6/tm0njqQgae1QGYuE+hsBQGeAQWzMUfBOb7pLdAwW?= =?us-ascii?Q?qfRLF1By4WjqDdUUjsMUwJm6c9+N3OTaADzBrsOK86bLGlwVIlc4lj2DmwK3?= =?us-ascii?Q?YpMmZ1EXgJlP8AX+LF2SFvwpdBsLB3IecZ1zfykyi5EoRBoxuXbRTiHAcG/5?= =?us-ascii?Q?Wd0hdw6ARrsIKEO/YUx+OHoH/5aBlqM0G8PkImh3SeOxibubHUE4h72tXIVR?= =?us-ascii?Q?GMiS/27L7AE58gFS4mAbgPBgQPoiaun66zPWtmZP7BlJ6H0nrKzR61qJJ9bi?= =?us-ascii?Q?R43iQyVsmWSAGo4HRKFt5mQysMKBUmu87pg65Ru0Qg36zBdAqtfQsLfwEj9e?= =?us-ascii?Q?fIT4aYxmpAKDNGvMa6JVQdYUGHW4fMkNzCTPGwkKhunCIg3kyQthwUP+H1vn?= =?us-ascii?Q?ThvWGzLLRenG4GnwnPgvifAsZFTCCSeFFwYRogUSp5cgI63703r+pJuJWEHU?= =?us-ascii?Q?VpHTzaX5xAKleBN/A5rHa81WO78sguqcskUPBiM1acoksUHsM3Y0Y1bQL8RP?= =?us-ascii?Q?NGhlpsvtUwY1UXcO45cS0Ci0U5Fss5ZxU7ZWaMycfv+LZux1PahqzMz+PvhN?= =?us-ascii?Q?Ew2BS94aeWNWk4bE+phCSoxicVi5TFLGKduiZAfgRY2cFw6US1XyZhyzU2Pf?= =?us-ascii?Q?E3POKFuTF66e0xM7NKTsTL/wwF+vqtLkArq/N2IUdS33wSY+nR3Flq1H4PMp?= =?us-ascii?Q?ljmQrG/HXO258P7dYEJVVwIYwfKOlafzXkGvSAlcRPWxKycwmX+ZZaH6i18I?= =?us-ascii?Q?ewpBNAqPFxBoUyVFAvlxdnSIpcd+LlJkpCdXebMNLVeYU9eD7uD0lcHSNR2B?= =?us-ascii?Q?1YitqY6zJbb+2q1PdOQddwdfQqcv3GG1DtuqNunEWaN8y6baYsfKm8FfCMSx?= =?us-ascii?Q?HCoUtR2J1gED+GbijMN9/50iBpmuzVcU7b0DLYuQDHwbaIW95thT8i3yrf3q?= =?us-ascii?Q?cRuGu4mqI5UNCSAMPadiGeu+YK8CfJVxTsv9?= 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)(1800799024)(7416014)(376014)(36860700013)(82310400026);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 May 2025 20:08:31.2064 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 4d72e028-5bc3-4427-27b9-08dd8c109b91 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: CH2PEPF000000A0.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR12MB9148 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250505_130840_726296_F66F7B33 X-CRM114-Status: GOOD ( 18.71 ) 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 02:28:13PM -0300, Jason Gunthorpe wrote: > On Mon, May 05, 2025 at 10:21:03AM -0700, Nicolin Chen wrote: > > > > > +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. > > That's no good, we can't have VMAs prevent cleaning up iommufd Hmm, would you please elaborate why? > objects, the right thing is to zap it with invalidate_mapping_range() Also, I can't find much info about invalidate_mapping_range(). Is it a user space call? I do see a few drivers defining a fault op in vm_operations_struct, where VM_FAULT_SIGBUS is returned when there is page backing up the VMAs. Is it what we need here? Thanks Nicolin