pgtable_walk
if (!pagetable->pgtbl_ops->pgtable_walk)
pagetable->pgtbl_ops->pgtable_walk(pagetable->pgtbl_ops, iova, &wd);
goto pgtable_walk;
pgtable_walk:
pgtable_walk(iommu, addr >> VTD_PAGE_SHIFT, bus, devfn, pgtable, level);
.pgtable_walk = arm_lpae_pgtable_walk,
int (*pgtable_walk)(struct io_pgtable_ops *ops, unsigned long iova, void *wd);