Re: [PATCH v8 10/14] iommu/arm-smmu-v3: Put the SVA mmu notifier in the smmu_domain

[Jason Gunthorpe <jgg@nvidia.com>]

On Mon, Jun 24, 2024 at 05:54:42PM +0800, Michael Shavit wrote:

> Can we leave a comment on ASID sharing in the code since it isn't
> added back until the next patch series? There are references to ASID
> sharing remaining (and even added in this commit) that don't make
> sense without this function (e.g "Prevent arm_smmu_share_asid() from
> trying to change the ASID").

Yes, I left the comment references because I really do expect it to
come back soon.

My plan, broadly, is to allow the domain's to be shared across smmu
instances which should introduce the infrastructure to avoid the
invalidation race in unshare by letting the domain have multiple ASIDs
at the same time.

After that we would add in vBTM support, this is BTM on systems that
only support S1 with no S2. This avoids the VMID issue that is
blocking it while still being useful.

pBTM would come after the IOMMUFD VIOMMU support that Nicolin is
working on as the VIOMMU would be the vehicle to bring in the KVM VMID
binding from userspace.

I can delete the comments too, but then someone will ask why not
delete all the locking as well. :\

Thanks,
Jason