XEN_BSHIFT
#define XEN_BSIZE (1 << XEN_BSHIFT)
(start >> XEN_BSHIFT);
first_sect = (ma & PAGE_MASK) >> XEN_BSHIFT;
nsects = nbytes >> XEN_BSHIFT;
first_sect = (ma & PAGE_MASK) >> XEN_BSHIFT;
nsects = nbytes >> XEN_BSHIFT;