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Why? The insert function is walking the page tables, it just updates things as they are. It learns the arragement for free while doing the walk. The device has to always provide consistent data, if it overlaps into pages that are already populated that is fine so long as it isn't changing their addresses. > And then if we can't support the full fault size, we'd need to > either presume a size and alignment of the next level or search for > contigous memory in both directions around the fault address, > perhaps unnecessarily as well. You don't really need to care about levels, the device should be faulting in the largest memory regions it can within its efficiency. If it works on 4M pages then it should be faulting 4M pages. The page size of the underlying CPU doesn't really matter much other than some tuning to impact how the device's allocator works. 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