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 nicolinc@nvidia.com
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