vm_object_pfn
pfn = vm_object_pfn(vmo, off);
pfn_t vm_object_pfn(vm_object_t *, uintptr_t);
pfn = vm_object_pfn(vmo, VMSM_OFFSET(vmsm, gpa));
vm_object_pfn(vmo, VMSM_OFFSET(vmsm, entry.vgie_gpa));