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Thu, 15 May 2025 19:05:47 -0700 Date: Thu, 15 May 2025 19:05:45 -0700 From: Nicolin Chen To: , Jason Gunthorpe CC: , , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v4 05/23] iommufd/driver: Let iommufd_viommu_alloc helper save ictx to viommu->ictx Message-ID: References: <5288cec9804e7e394be3b7de6b246d8ca9c4792a.1746757630.git.nicolinc@nvidia.com> <20250514170637.GE382960@nvidia.com> Precedence: bulk X-Mailing-List: linux-tegra@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20250514170637.GE382960@nvidia.com> X-NV-OnPremToCloud: AnonymousSubmission X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL6PEPF00022574:EE_|MN0PR12MB6318:EE_ X-MS-Office365-Filtering-Correlation-Id: 256ba30f-cbef-42f9-724b-08dd941e36cd X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700013|1800799024|82310400026|376014|7416014; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 May 2025 02:06:04.3801 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 256ba30f-cbef-42f9-724b-08dd941e36cd X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BL6PEPF00022574.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN0PR12MB6318 On Wed, May 14, 2025 at 02:06:37PM -0300, Jason Gunthorpe wrote: > On Thu, May 08, 2025 at 08:02:26PM -0700, Nicolin Chen wrote: > > When an IOMMU driver calls iommufd_viommu_alloc(), it must pass in an ictx > > pointer as the underlying _iommufd_object_alloc() helper function requires > > that to allocate a new object. However, neither the iommufd_viommu_alloc() > > nor its underlying _iommufd_object_alloc() saves the ictx in the allocated > > viommu object, although viommu could hold an ictx pointer. > > > > When the IOMMU driver wants to use another iommufd function passing in the > > allocated viommu, it could have avoided passing in the ictx pointer again, > > if viommu->ictx is valid. > > > > Save ictx to viommu->ictx in the iommufd_viommu_alloc(), in order to ease > > a new vIOMMU-based helper that would then get the ictx from viommu->ictx. > > > > Signed-off-by: Nicolin Chen > > --- > > include/linux/iommufd.h | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > It is OK, but please think carefully if the ictx is actually > needed. The reason most objects don't have an ictx in them is because > their contexts are always inside an ioctl so they get the ictx from > there. > > We don't have a lot of viommu allocations so it isn't such a big deal, > but just generally that is how it was built that the ictx comes from > the ioctl not the object. It's more of providing cleaner for-driver APIs. Especially with the new ucmd changes, it can be just: // in my_viommu_alloc() my_viommu = iommufd_viommu_alloc(ucmd, ...); iommufd_viommu_alloc_mmap(my_viommu, ...); iommufd_viommu_destroy_mmap(my_viommu, ...); // in my_viommu_destory() iommufd_viommu_destroy_mmap(my_viommu, ...); Otherwise, they would be something like: // in my_viommu_alloc() my_viommu = iommufd_viommu_alloc(ucmd, ...); iommufd_viommu_alloc_mmap(ucmd->ictx, my_viommu, ...); iommufd_viommu_destroy_mmap(ucmd->ictx, my_viommu, ...); // in my_viommu_destory() iommufd_viommu_destroy_mmap(my_viommu->ictx, my_viommu ...); That being said, I ended up doing something more in this patch for the ucmd rework and Kevin's comments: diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h index 98fe5a49c9606..ddd144031af5d 100644 --- a/drivers/iommu/iommufd/iommufd_private.h +++ b/drivers/iommu/iommufd/iommufd_private.h @@ -136,14 +136,6 @@ int iopt_pin_pages(struct io_pagetable *iopt, unsigned long iova, void iopt_unpin_pages(struct io_pagetable *iopt, unsigned long iova, unsigned long length); -struct iommufd_ucmd { - struct iommufd_ctx *ictx; - void __user *ubuffer; - u32 user_size; - void *cmd; - struct iommufd_object *alloced_obj; -}; - int iommufd_vfio_ioctl(struct iommufd_ctx *ictx, unsigned int cmd, unsigned long arg); diff --git a/drivers/iommu/iommufd/viommu.c b/drivers/iommu/iommufd/viommu.c index 416cd281eb2b5..6c0a2a0885a32 100644 --- a/drivers/iommu/iommufd/viommu.c +++ b/drivers/iommu/iommufd/viommu.c @@ -60,9 +60,14 @@ int iommufd_viommu_alloc_ioctl(struct iommufd_ucmd *ucmd) goto out_put_hwpt; } + /* The iommufd_viommu_alloc helper saves ucmd->ictx in viommu->ictx */ + if (WARN_ON_ONCE(viommu->ictx != ucmd->ictx)) { + rc = -EINVAL; + goto out_put_hwpt; + } + xa_init(&viommu->vdevs); viommu->type = cmd->type; - viommu->ictx = ucmd->ictx; viommu->hwpt = hwpt_paging; refcount_inc(&viommu->hwpt->common.obj.users); INIT_LIST_HEAD(&viommu->veventqs); diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h index a24b924cf6872..74d11c6779739 100644 --- a/include/linux/iommufd.h +++ b/include/linux/iommufd.h @@ -52,6 +52,14 @@ struct iommufd_object { unsigned int id; }; +struct iommufd_ucmd { + struct iommufd_ctx *ictx; + void __user *ubuffer; + u32 user_size; + void *cmd; + struct iommufd_object *alloced_obj; +}; + struct iommufd_device *iommufd_device_bind(struct iommufd_ctx *ictx, struct device *dev, u32 *id); void iommufd_device_unbind(struct iommufd_device *idev); @@ -252,8 +260,10 @@ static inline int iommufd_viommu_report_event(struct iommufd_viommu *viommu, static_assert(offsetof(drv_struct, member.obj) == 0); \ ret = (drv_struct *)_iommufd_object_alloc_ucmd( \ ucmd, sizeof(drv_struct), IOMMUFD_OBJ_VIOMMU); \ - if (!IS_ERR(ret)) \ + if (!IS_ERR(ret)) { \ ret->member.ops = viommu_ops; \ + ret->member.ictx = ucmd->ictx; \ + } \ ret; \ }) #endif Thanks Nicolin