In case of evtchn buffer overflow (received more than 1024 events between
libvchan_wait calls) further reads returns ERROR_IO_DEVICE. The only way to
recover from that is to reset the buffer. Because vchan code doesn't take care
of number of fired events - only the fact that some event was fired - lost
events here shouldn't break anything. Events reported _after_ libvchan_wait
call will be collected and reported correctly.
Some more comments in the code (here and in qrexec-agent in the next commit).
cb5479666c