Hi Christoph, On Thu, 15 Apr 2021 07:44:59 +0100, Christoph Hellwig <h...@infradead.org> wrote:
> > * > > * 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? It was removed in my v1 but thought it would be cleaner if we treat iommu_sva_alloc_pasid() as a leaf function of iommu_sva_bind_device(). Then we don't have to do get_task_mm() every time. But to your point below, it is better to get low-level driver handle it. > > > @@ -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. The mm users reference is just for precaution, in case low level driver use kthread etc. I agree it is cleaner to just remove mm here, let the low-level driver deal with it. Let me give it a spin. Thanks, Jacob