It looks incorrect also to me. I think the kernel mapping is accessed by
netmap (kernel) at least to touch the netmap_ring structs, and initialize
netmap_if structs (in some cases, VALE can also touch the netmap buffers).
But I may be misunderstanding, since "extmem" is a kind of recent addition.
Maybe Giuseppe can shed a light on this matter.
You are both right and the new comment (mentioning munmap()) is correct.