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

[Tian, Kevin]

> From: Nicolin Chen <nicolinc@xxxxxxxxxx>
> 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@xxxxxxxxxx>

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