Re: [PATCH v6 13/18] iommu/vt-d: Handle reattach of the restored domain

[Baolu Lu]

On 10/30/26 06:34, Samiullah Khawaja wrote:
> > > diff --git a/drivers/iommu/intel/liveupdate.c b/drivers/iommu/intel/ 
> > > liveupdate.c
> > > index 36816d3651e6..665ebb81bd61 100644
> > > --- a/drivers/iommu/intel/liveupdate.c
> > > +++ b/drivers/iommu/intel/liveupdate.c
> > > @@ -394,6 +394,137 @@ void 
> > > intel_iommu_handle_drhd_restore_failure(struct intel_iommu *iommu)
> > >                iommu->name);
> > >  }
> > > +static void domain_detach_restored_iommu(struct dmar_domain *domain,
> > > +                     struct intel_iommu *iommu)
> > > +{
> > > +    struct iommu_domain_info *info;
> > > +
> > > +    guard(mutex)(&iommu->did_lock);
> > > +    info = xa_load(&domain->iommu_array, iommu->seq_id);
> > > +    if (--info->refcnt == 0) {
> > > +        xa_erase(&domain->iommu_array, iommu->seq_id);
> > > +        kfree(info);
> > > +    }
> >
> > This seems to be different from normal domain_detach_iommu(), which
> > looks like this,
> >
> >        if (--info->refcnt == 0) {
> >                ida_free(&iommu->domain_ida, info->did);
> >                xa_erase(&domain->iommu_array, iommu->seq_id);
> >                kfree(info);
> >        }
> >
> > why ida_free() is skipped in the restored path?
>
> The restored device can be removed and probed again while the PASID and
> context entries stay intact. So the restored did is not freed in this
> path. Once the domain is reclaimed by the iommufd, then it takes the
> normal detach path.

Can you please add a comment to explain this?

Thanks,
baolu