hmm_pfn_to_map_order
size = 1UL << hmm_pfn_to_map_order(hmm_pfn);
if (hmm_pfn_to_map_order(range->hmm_pfns[0])) {
args->p.page = hmm_pfn_to_map_order(range->hmm_pfns[0]) +
hmm_order = hmm_pfn_to_map_order(range.hmm_pfns[pfn_index]);
if (hmm_pfn_to_map_order(entry) + PAGE_SHIFT == PMD_SHIFT)
else if (hmm_pfn_to_map_order(entry) + PAGE_SHIFT == PUD_SHIFT)