Fix assert condition in pmap_large_unmap()

[scottph]

Summary

pmap_large_unmap() asserts that an unmapping request covers the
entirety of a 2 MByte or 1 GByte page. The logic in the asserts
was out of date with the loop logic though, asserting on valid
unmap requests when where these larger pages were in use.

Test Plan

kldload/kldunload nvdimm.ko

[alc]

sys/amd64/amd64/pmap.c

8444 ↗

(On Diff #51133)

I would actually suggest rewriting this assertion to be

va + NBPDP <= sva + len

In other words, destroying the current superpage mapping does not unmap addresses beyond those requested by the caller.

I speculate that at one point in the development of this function len was the residual number of bytes left to unmap on each iteration. Then, the current assertion would have made sense.

8460 ↗

(On Diff #51133)

And, similarly

va + NBPDR <= sva + len

[kib]

sys/amd64/amd64/pmap.c

8444 ↗

(On Diff #51133)

I agree, this is the correct fix.

[scottph]

Fix assert to use va loop variable.