On s390, the vmexit event has a tree-like structure: between
exit_event_begin and exit_event_end several other events may happen and
with each of them refining the previous ones.

This patch adds a decoder for such events to the generic code and also
the files <asm/kvm_perf.h> and kvm-stat.c for s390.

Commands 'perf kvm stat record', 'report' and 'live' are supported.
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Alexander Yarygin <yarygin@linux.vnet.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1404397747-20939-5-git-send-email-yarygin@linux.vnet.ibm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>