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

Jason Gunthorpe
2025-02-18T13:03:37Z

On Sat, Feb 15, 2025 at 05:53:13PM +0800, Baolu Lu wrote:
> On 2/14/25 20:41, Jason Gunthorpe wrote:
> > On Fri, Feb 14, 2025 at 01:39:52PM +0800, Baolu Lu wrote:
> >
> > > When the IOMMU is working in scalable mode, PASID and PRI are supported.
> > > ATS will always be enabled, even if the identity domain is attached to
> > > the device, because the PASID might use PRI, which depends on ATS
> > > functionality. This might not be the best choice, but it is the
> > > simplest and functional.
> > The arm driver keeps track of things and enables ATS when PASIDs are
> > present
>
> I am not aware of any VT-d hardware implementation that supports
> scalable mode but not PASID. If there were one, it would be worthwhile
> to add an optimization to avoid enabling ATS during probe if PASID is
> not supported.

I mean domains attached to PASIDs that need PRI/ATS/etc

> > Although, I'm wondering now, that check should be on the SVA paths as
> > well as the iommufd path..
>
> That appears to be a fix.

Does SVA have the same issue?

Jason