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

[Jason Gunthorpe <jgg@nvidia.com>]

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>
> ---
>  drivers/pci/pci-acpi.c | 13 +++++++--
>  drivers/pci/pci.c      | 65 +++++++++++++++++++++++++++++++++++++-----
>  drivers/pci/quirks.c   | 19 +++++++++++-
>  3 files changed, 87 insertions(+), 10 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

Jason