drm_gpusvm_hmm_pfn_to_order
order = drm_gpusvm_hmm_pfn_to_order(pfns[i], i, npages);
i += 0x1 << drm_gpusvm_hmm_pfn_to_order(pfns[i], i, npages);
i += 1ul << drm_gpusvm_hmm_pfn_to_order(pfns[i], i, npages);