VTOPOFF
uw->buffer.offset = VTOPOFF(pkt);
ur->buffer.offset = VTOPOFF(pkt);
pxe_command_buf_off = VTOPOFF(pxe_command_buf);
uw->buffer.offset = VTOPOFF(pkt);
ur->buffer.offset = VTOPOFF(pkt);
pxe_command_buf_off = VTOPOFF(pxe_command_buf);