RGOFSET
#define VA_ROUNDDOWNTOREG(va) ((int)(va) & ~RGOFSET)
baseoff = (u_int)base & RGOFSET;
i = (baseoff + len + RGOFSET) >> RGSHIFT;
baseoff = (u_int)base & RGOFSET;
i = (baseoff + len + RGOFSET) >> RGSHIFT;