Re: [PATCH v1 12/14] iommu/arm-smmu-v3: Support IOMMU_DOMAIN_NESTED type of allocations

[Jason Gunthorpe]

On Fri, Mar 24, 2023 at 04:44:58PM +0100, Eric Auger wrote:

> Please can you explain the (use) case where !parent. This creates an
> unmanaged S1?

If parent is not specified then userspace can force the IOPTE format
to be S1 or S2 of a normal unmanaged domain.

Not sure there is a usecase, but it seems reasonable to support. It
would be useful if there is further parameterization of the S1 like
limiting the number of address bits or something.

Jason