[PATCH RFC] iommu: Enable per-device SSID space for SVA

[Jason Gunthorpe]

On Tue, May 12, 2026 at 02:51:38PM +0000, Joonwon Kang wrote:

> Appreciate all your clarifications here. So, my understanding is that if
> our system does not support ST64BV and ST64BV0 or if our device does not
> distinguish between the posted write and the non-posted write regarding
> PASID, then we can lift the use of the global PASID space. Can I say this?

You should do what Robin said - just have your driver use a per-device
PASID that it allocates and never use the global pasid allocator.

To do this lightly re-organize the SVA code so the driver can supply
its own PASID, and in this mode we wouldn't activate the ENQCMD
features in the mm.

Jason