Re: [PATCH v7 5/5] PCI: Suspend iommu function prior to resetting a device

[Nicolin Chen <nicolinc@nvidia.com>]

On Wed, Nov 26, 2025 at 03:43:13PM -0600, Bjorn Helgaas wrote:
> On Fri, Nov 21, 2025 at 05:57:32PM -0800, Nicolin Chen wrote:
> > PCIe permits a device to ignore ATS invalidation TLPs while processing a
> > reset. This creates a problem visible to the OS where an ATS invalidation
> > command will time out: e.g. an SVA domain will have no coordination with a
> > reset event and can racily issue ATS invalidations to a resetting device.
> > 
> > The PCIe r6.0, sec 10.3.1 IMPLEMENTATION NOTE recommends SW to disable and
> > block ATS before initiating a Function Level Reset. It also mentions that
> > other reset methods could have the same vulnerability as well.
> > 
> > The IOMMU subsystem provides pci_dev_reset_iommu_prepare/done() callback
> > helpers for this matter. Use them in all the existing reset functions.
> > 
> > This will attach the device to its iommu_group->blocking_domain during the
> > device reset, so as to allow IOMMU driver to:
> >  - invoke pci_disable_ats() and pci_enable_ats(), if necessary
> >  - wait for all ATS invalidations to complete
> >  - stop issuing new ATS invalidations
> >  - fence any incoming ATS queries
> > 
> > Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> > Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
> 
> Acked-by: Bjorn Helgaas <bhelgaas@google.com>

Thanks!!