[PATCH RFCv1 07/14] iommufd: Add viommu set/unset_dev_id ops

[Tian, Kevin]

> From: Jason Gunthorpe <jgg at nvidia.com>
> Sent: Wednesday, May 22, 2024 2:25 AM
> 
> On Tue, May 14, 2024 at 06:59:07PM -0700, Nicolin Chen wrote:
> > So, you want a proxy S1 domain for a device to attach, in case
> > of a stage-2 only setup, because an S2 domain will no longer has
> > a VMID, since it's shared among viommus. In the SMMU driver case,
> > an arm_smmu_domain won't have an smmu pointer, so a device can't
> > attach to an S2 domain but always an nested S1 domain, right?
> 
> That seems like a simple solution to the VMID lifetime, but it means
> the kernel has to decode more types of vSTE.
> 

why does ATC invalidation need to know about VMID?

Or is above talking about beyond the discussion between DEV_INVALIDATE
vs. VIOMMU_INVALIDATE?