perf intel-pt: Refine kernel decoding only warning message

Stop the message displaying when user space is not being traced.

Example:

  Prerequisites:

    sudo setcap "cap_sys_rawio,cap_sys_admin,cap_sys_ptrace,cap_syslog,cap_ipc_lock=ep" ~/bin/perf
    sudo chmod +r /proc/kcore

  Before:

    $ perf record --no-switch-events --kcore -a -e intel_pt//k -- sleep 0.001
    Warning:
    Intel Processor Trace decoding will not be possible except for kernel tracing!
    [ perf record: Woken up 1 times to write data ]
    [ perf record: Captured and wrote 0.838 MB perf.data ]

  After:

    $ perf record --no-switch-events --kcore -a -e intel_pt//k -- sleep 0.001
    [ perf record: Woken up 1 times to write data ]
    [ perf record: Captured and wrote 1.068 MB perf.data ]

    $ sudo chmod go-r /proc/kcore
    $ sudo setcap -r ~/bin/perf
Signed-off-by: NAdrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: http://lore.kernel.org/lkml/20200528120859.21604-2-adrian.hunter@intel.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/arch/x86/util/intel-pt.c

@@ -883,7 +883,8 @@ static int intel_pt_recording_options(struct auxtrace_record *itr,
 	 * per-cpu with no sched_switch (except workload-only).
 	 */
 	if (!ptr->have_sched_switch && !perf_cpu_map__empty(cpus) &&
-	    !target__none(&opts->target))
+	    !target__none(&opts->target) &&
+	    !intel_pt_evsel->core.attr.exclude_user)
 		ui__warning("Intel Processor Trace decoding will not be possible except for kernel tracing!\n");
 
 	return 0;