EVTCHN_FIFO_LINK_BITS  268 include/xen/interface/event_channel.h #define EVTCHN_FIFO_LINK_MASK ((1 << EVTCHN_FIFO_LINK_BITS) - 1)
EVTCHN_FIFO_LINK_BITS  270 include/xen/interface/event_channel.h #define EVTCHN_FIFO_NR_CHANNELS (1 << EVTCHN_FIFO_LINK_BITS)