PX_BUF_SIZE
bva = (char *)uvm_pageboot_alloc(PX_BUF_SIZE + PX_BUF_ALIGN);
if (bpa + PX_BUF_SIZE > 8192*1024)
if (uvm_pglistalloc(PX_BUF_SIZE, 0, 8192*1024, PX_BUF_ALIGN,
si->si_buf_size = PX_BUF_SIZE;
memset(si->si_buf, 0, PX_BUF_SIZE);