perf tools: Give user better message if precise is not supported

Platforms (e.g., VM's) without support for precise mode get a confusing
error message. e.g.,
$ perf record -e cycles:p -a -- sleep 1

  Error: sys_perf_event_open() syscall returned with 95 (Operation not
  supported).  /bin/dmesg may provide additional information.

  No hardware sampling interrupt available. No APIC? If so then you can
  boot the kernel with the "lapic" boot parameter to force-enable it.
  sleep: Terminated

which is not clear that precise mode might be the root problem. With this
patch:

$ perf record -e cycles:p -fo /tmp/perf.data -- sleep 1
  Error:
  'precise' request may not be supported. Try removing 'p' modifier
  sleep: Terminated

v2: softened message to 'may not be' supported per Robert's suggestion

Signed-off-by: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Robert Richter <robert.richter@amd.com>
Link: http://lkml.kernel.org/r/1347569955-54626-4-git-send-email-dsahern@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 9 insertions, 0 deletions

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 73b5d7f91194..53c9892e96dd 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -317,6 +317,11 @@ try_again:
                                           perf_evsel__name(pos));
                                 rc = -err;
                                 goto out;
+                        } else if ((err == EOPNOTSUPP) && (attr->precise_ip)) {
+                                ui__error("\'precise\' request may not be supported. "
+                                          "Try removing 'p' modifier\n");
+                                rc = -err;
+                                goto out;
                         }
 
                         printf("\n");
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index fb9da71eba1f..f2ecd498c72d 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -977,6 +977,10 @@ try_again:
                                 ui__error("Too many events are opened.\n"
                                             "Try again after reducing the number of events\n");
                                 goto out_err;
+                        } else if ((err == EOPNOTSUPP) && (attr->precise_ip)) {
+                                ui__error("\'precise\' request may not be supported. "
+                                          "Try removing 'p' modifier\n");
+                                goto out_err;
                         }
 
                         ui__error("The sys_perf_event_open() syscall "