[PATCH v4 00/12] Initial support for SMMUv3 nested translation

[Jason Gunthorpe]

On Fri, Feb 21, 2025 at 04:28:50AM +0000, Tian, Kevin wrote:
> > With PASID support, multiple domains can be attached to the device, and
> > each domain may have different ATS requirements.  Therefore, we cannot
> > simply determine the ATS status in the RID domain attach/detach paths. A
> > better solution is to use the reference count, as mentioned above.
> > 
> 
> Okay, that helps connect the dots and makes sense to me. Thanks!

I also have this general feeling that using ATS or not should be some
user policy (ie with sysfs or something) not just always automatic..

Right now on our devices there is a firmware config that hides the ATS
support from PCI config space and the general guidance is to only turn
it on in very specific situations.

Jason