[PATCH v3 2/3] PCI: Allow ATS to be always on for pre-CXL devices

[Jason Gunthorpe]

On Fri, Mar 06, 2026 at 03:41:16PM -0800, Nicolin Chen wrote:
> Some NVIDIA GPU/NIC devices, although don't implement the CXL config space,
> they have many CXL-like properties. Call this kind "pre-CXL".
> 
> Similar to CXL.cache capaiblity, these pre-CXL devices also require the ATS
> function even when their RIDs are IOMMU bypassed, i.e. keep ATS "always on"
> v.s. "on demand" when a non-zero PASID line gets enabled in SVA use cases.
> 
> Introduce pci_dev_specific_ats_always_on() quirk function to scan a list of
> IDs for these device. Then, include it pci_ats_always_on().
> 
> Suggested-by: Jason Gunthorpe <jgg at nvidia.com>
> Signed-off-by: Nicolin Chen <nicolinc at nvidia.com>
> ---
>  drivers/pci/pci.h    |  9 +++++++++
>  drivers/pci/ats.c    |  3 ++-
>  drivers/pci/quirks.c | 26 ++++++++++++++++++++++++++
>  3 files changed, 37 insertions(+), 1 deletion(-)

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

Jason