> From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Sent: Thursday, February 9, 2023 9:24 PM
>
> On Thu, Feb 09, 2023 at 03:23:47AM +0000, Tian, Kevin wrote:
> > > From: Nicolin Chen <nicolinc@xxxxxxxxxx>
> > > Sent: Wednesday, February 8, 2023 5:18 AM
> > >
> > > Because list_del() is together with iopt_table_remove_domain(), it makes
> > > sense to have list_add_tail() together with iopt_table_add_domain().
> > >
> > > Also place the mutex outside the iommufd_device_do_attach() call,
> similar
> > > to what's in the iommufd_device_auto_get_domain() function.
> > >
> > > Co-developed-by: Yi Liu <yi.l.liu@xxxxxxxxx>
> > > Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
> > > Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
> > > Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> >
> > shouldn't this be a separate bug fix and backported? double adding a
> > list item would certainly clobber the list...
>
> AFAIK there is no bug, this is just reorganizing things
>
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?
with this patch the hwpt is added to the list only when it's attached
by the first device, i.e. when iopt_table_add_domain() is called.
if (!iommufd_hw_pagetable_has_group(hwpt, idev->group)) {
rc = iommu_attach_group(hwpt->domain, idev->group);
if (rc)
goto out_iova;
if (list_empty(&hwpt->devices)) {
rc = iopt_table_add_domain(&hwpt->ioas->iopt,
hwpt->domain);
if (rc)
goto out_detach;
list_add_tail(&hwpt->hwpt_item, &hwpt->ioas->hwpt_list);
}
}
so it's actually a bug fix.
