After more digging, I bet it's a paging-structure-cache flush bug. I've debugged these before, and they're nasty, hardware dependent, hard-to-reproduce issues. Looks like the code that the AI flagged might actually be wrong, but not for the reason that the AI thought.

https://lore.kernel.org/all/CALCETrXbj__SFQMzPZhES5y6-sh4np-...