Re: [PATCH v2 3/7] iommu: Add iommu_report_device_broken() to quarantine a broken device

Nicolin Chen
2026-03-19T03:14:08Z

On Thu, Mar 19, 2026 at 02:35:33AM +0000, Tian, Kevin wrote:
> > > > + scoped_guard(mutex, &group->mutex) {
> > > > + /* Do not block the device again if it has been recovered */
> > > > + if (!READ_ONCE(group->requires_reset))
> > > > + goto out_put;
> > > > + if (list_is_singular(&group->devices)) {
> > > > + /* Note: only support group with a single device */
> > >
> > > this series is about fixing a vulnerability. Then it sounds incomplete to
> > > leave certain configuration still under risk. Probably we should first
> > > ensure ATS can be enabled only in singleton group, just like how we
> > > did for pci_enable_pasid()?
> >
> > I understand your concern. But I am not very sure about applying
> > limitation to ATS support. Would this block some existing cases?
>
> what about just throwing out a message to warn that enabling ATS
> in a non-singleton iommu group may suffer from unquarantined
> situation if any device in the group triggers a ATC invalidation timeout?

Yes. Baolu suggested the same, we could move this condition into
iommu_report_device_broken().

> > > > + /*
> > > > + * Quarantine the device completely. This will be cleared
> > > > upon
> > > > + * a pci_dev_reset_iommu_done() call indicating the recovery.
> > > > + */
> > > > + pci_dev_lock(pdev);
> > > > + pci_dev_reset_iommu_prepare(pdev);
> > >
> > > let's rename it to iommu_quarantine_device() to be called here. then
> > > have another wrapper pci_dev_reset_iommu_prepare() to call it too.
> > >
> > > this path has nothing to do with reset.
> >
> > But the implementation of that iommu_quarantine_device would be
> > still to shift to resetting_domain. Perhaps, we can rename that
> > to quarantine_domain or so.
>
> yes let's rename that too. the purpose of this function is clearly about
> quarantine. reset is just one user of it.

OK. I will make it happen.

Nicolin