Hi Jean, On Fri, 9 Apr 2021 11:03:05 -0700, Jacob Pan <jacob.jun....@linux.intel.com> wrote:
> > problems: > > > > * We don't have a use-case for binding the mm of a remote process (and > > it's supposedly difficult for device drivers to do it securely). So > > OK, we remove the mm argument from iommu_sva_bind_device() and use the > > current mm. But the IOMMU driver isn't going to do > > get_task_mm(current) every time it needs the mm being bound, it will > > take it from iommu_sva_bind_device(). Likewise iommu_sva_alloc_pasid() > > shouldn't need to bother with get_task_mm(). > > > > * cgroup accounting for IOASIDs needs to be on the current task. > > Removing the mm parameter from iommu_sva_alloc_pasid() doesn't help > > with that. Sure it indicates that iommu_sva_alloc_pasid() needs a > > specific task context but that's only for cgroup purpose, and I'd > > rather pass the cgroup down from iommu_sva_bind_device() anyway (but am > > fine with keeping it within ioasid_alloc() for now). Plus it's an > > internal helper, easy for us to check that the callers are doing the > > right thing. > With the above split, we really just have one allocation function: > ioasid_alloc(), so it can manage current cgroup accounting within. Would > this work? After a few attempts, I don't think the split can work better. I will restore the mm parameter and add a warning if mm != current->mm. Thanks, Jacob
