On Fri, Dec 19, 2025 at 11:16:08AM -0400, Jason Gunthorpe wrote:

On Thu, Dec 18, 2025 at 12:26:49PM -0800, Nicolin Chen wrote:

quoted

Currently, ASID is allocated per smmu_domain, stored in the domain, and
freed with the domain.

Practically, ASID is only used in a CD as an iotlb tag. Therefore, ASID
doesn't really follow the life cycle of a domain but domain attachment.

On the other hand, the CD carrying ASID is installed to a device's STE.

This applies to the VMID as well, which is installed in an STE directly.

Since a device can only have one ASID per SSID and one VMID per SID, add
an ASID array and VMID in the arm_smmu_master structure, to decouple the
ASID/VMID from the domain structure.

I don't think this is entirely right..

When a S1 is attached to a master the master needs to store the VMID
it is using, as the VMID is global to the STE and effectively becomes
global to the master.

But the ASID should be stored in the invalidation list of the domain.

Hmm, you mean the nested case (host VMID + guest ASID), right?

But in that case, the guest-level ASID isn't needed anywhere in
the host driver? The ASID should be configured in a guest-level
CD. And the invalidation command directly coming from the guest
is already filled with the guest-level ASID.

Also, the invalidation array stores either ASID or VMID, there
is no case of storing both, right?

Jus search the list for the (instance, vmid) pair of the master to get
back the right ASID.

We don't need to store it again in another list, that's confusing.

Okay. I was trying to get rid of the extra for loop searching
for an ID in the array. That's why I had the alloc_id/free_id
ops too, so everything would be done in existing two loops in
the merge/unref functions.

Nicolin