Back in 2022 I posted a bug report that may relate to this area of the code.
You can find the original email by searching the archive for "Possible PMD" and looking for me as sender. Briefly, it had to do with trying to map 1Gb region, properly aligned. At the time, 1G pages were not supported, so I expected to get all 2M pages. What happened is that all but one were 2G and last 2G was mapped as individual 4K pages. Seems like some kind of off-by-one problem somewhere in the code. Since you're deep into this part of things, I thought I might mention this again :-) ... Best wishes - Eliot Moss
