RE: [PATCH v6 5/5] PCI: Suspend iommu function prior to resetting a device

Tian, Kevin
2025-11-21T07:59:40Z

> From: Nicolin Chen <nicolinc@nvidia.com>
> Sent: Wednesday, November 19, 2025 8:52 AM
>
> 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
>
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>

Reviewed-by: Kevin Tian <kevin.tian@intel.com>