perf evsel: Add verbose output for sys_perf_event_open fallback

perf evsel: Add verbose output for sys_perf_event_open fallback

Adding info about what is being switched off in the sys_perf_event_open
fallback.

New output (notice the 'switching off' lines):

  $ perf stat -e '{cycles,instructions}' -vvv ls
  Using CPUID GenuineIntel-6-3D
  intel_pt default config: tsc
  ------------------------------------------------------------
  perf_event_attr:
    size                             112
    sample_type                      IDENTIFIER
    read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING|ID|GROUP
    disabled                         1
    inherit                          1
    enable_on_exec                   1
    exclude_guest                    1
  ------------------------------------------------------------
  sys_perf_event_open: pid 3591  cpu -1  group_fd -1  flags 0x8
  sys_perf_event_open failed, error -22
  switching off cloexec flag
  ------------------------------------------------------------
  perf_event_attr:
    size                             112
    sample_type                      IDENTIFIER
    read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING|ID|GROUP
    disabled                         1
    inherit                          1
    enable_on_exec                   1
    exclude_guest                    1
  ------------------------------------------------------------
  sys_perf_event_open: pid 3591  cpu -1  group_fd -1  flags 0
  sys_perf_event_open failed, error -22
  switching off exclude_guest, exclude_host
  ------------------------------------------------------------
  perf_event_attr:
    size                             112
    sample_type                      IDENTIFIER
    read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING|ID|GROUP
    disabled                         1
    inherit                          1
    enable_on_exec                   1
  ------------------------------------------------------------
  sys_perf_event_open: pid 3591  cpu -1  group_fd -1  flags 0
  sys_perf_event_open failed, error -22
  switching off sample_id_all
  ------------------------------------------------------------
  perf_event_attr:
    size                             112
    sample_type                      IDENTIFIER
    read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING|ID|GROUP
    disabled                         1
    inherit                          1
    enable_on_exec                   1
  ...

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20170721121212.21414-2-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>