Re: [PATCH v2 2/2] iommu/sva: Remove mm parameter from SVA bind API

Christoph Hellwig
2021-04-15T06:45:13Z

> *
> * Returns 0 on success and < 0 on error.
> @@ -28,6 +28,9 @@ int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
> int ret = 0;
> ioasid_t pasid;
>
> + if (mm != current->mm)
> + return -EINVAL;
> +

Why not remove the parameter entirely?

> @@ -2989,8 +2990,11 @@ iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, unsigned int fla
> return ERR_PTR(-ENODEV);
>
> /* Supervisor SVA does not need the current mm */
> - if ((flags & IOMMU_SVA_BIND_SUPERVISOR) && mm)
> - return ERR_PTR(-EINVAL);
> + if (!(flags & IOMMU_SVA_BIND_SUPERVISOR)) {
> + mm = get_task_mm(current);
> + if (!mm)
> + return ERR_PTR(-EINVAL);
> + }

I don't see why we need the reference. I think we should just stop
passing the mm to ->sva_bind and let the low-level driver deal with
any reference to current->mm where needed.