XEN_PFN_UP
unsigned int i, n_pages = XEN_PFN_UP(size);
unsigned int i, n_pages = XEN_PFN_UP(dma_offset + size);
unsigned int i, n_pages = XEN_PFN_UP(dma_offset + size);
unsigned int i, n_pages = XEN_PFN_UP(size);
unsigned int i, nr_pages = XEN_PFN_UP(xen_offset_in_page(p) + size);
return XEN_PFN_UP(xen_offset_in_page(start) + len);