[RFC PATCH v4 03/16] iommu/arm-smmu-v3: Add initial pSMMU realm viommu plumbing

[Jason Gunthorpe]

On Tue, Sep 01, 2026 at 12:08:38PM -0700, Nicolin Chen wrote:

> The viommu object here is an empty vehicle that almost has no use
> but to allow another vehicle (vdevice) on top to forward vBDF. It
> makes VMM code a bit awkward: there is no iommu instance, so VMM
> doesn't enable iommu driver, then there is no good place to alloc
> the viomu object for VIOMMU_TYPE_ARM_REALM_SMMUV3.

It would have to allocate singletons viommu for each psmmu as part of
setting up the vdevices.

Somehow I'd rather the vmm deal with that then invent a whole new set
of uapis and flows..

At best maybe we can invent a kernel side helper to create the
singletons like the auto domains, but IDK if it is really so hard for
the VMM (especially compared with how hard everything else is in CC)

Jason