On existing hardware it is mostly useless from a security point of view, but if you design new hardware it is way simpler to have per device physical base+lengh

On existing hardware it is mostly useless from a security point of view, but if you design new hardware it is way simpler to have per device physical base+lenght limits than a full featured IOMMU. This is to be restricted to somehow light embedded devices though. For a generalist expensible computer it would not make sense.