We are not space constrained here, i.e., we are not trying to come up with a short phrase that fits on the same as a #define, so I would argue that we unambiguously spell out what we mean.
Try to make the uma_reserve_kva() clearer: don't mention VM objects
at all since it doesn't really make sense to mention such details
in a public header. Fix the comment above noobj_alloc().