> From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Sent: Saturday, February 11, 2023 5:17 AM
>
> >
> > there is semantics change.
> >
> > here is the current code:
> >
> > case IOMMUFD_OBJ_HW_PAGETABLE: {
> > struct iommufd_hw_pagetable *hwpt =
> > container_of(pt_obj, struct iommufd_hw_pagetable,
> obj);
> >
> > rc = iommufd_device_do_attach(idev, hwpt);
> > if (rc)
> > goto out_put_pt_obj;
> >
> > mutex_lock(&hwpt->ioas->mutex);
> > list_add_tail(&hwpt->hwpt_item, &hwpt->ioas->hwpt_list);
> > mutex_unlock(&hwpt->ioas->mutex);
> > break;
> > }
> >
> > Above means every attach to hwpt will try to add the hwpt to the
> > list tail. Isn't it a bug?
>
> Yes, that looks like a bug..
>
> But this patch isn't the right way to fix that.
>
> The HWPT should be permanently linked to the IOAS as long as it
> exists, and the linkage should happen when it is first created.
>
> So attaching a HWPT to another device should never re-link it to the
> ioas, thus delete these lines here.
>
yes, this makes more sense
