perf tools: Check fallback error and order

The perf_event_open might fail due to various reasons, so blindly
reducing precise_ip level might not be the best way to deal with it.

It seems the kernel return -EOPNOTSUPP when PMU doesn't support the
given precise level.  Let's try again with the correct error code.

This caused a problem on AMD, as it stops on precise_ip of 2 for IBS but
user events with exclude_kernel=1 cannot make progress.  Let's add the
evsel__handle_error_quirks() to this case specially.  I plan to work on
the kernel side to improve this situation but it'd still need some
special handling for IBS.

Reviewed-by: James Clark <james.clark@linaro.org>
Reviewed-by: Ravi Bangoria <ravi.bangoria@amd.com>
Acked-by: Kan Liang <kan.liang@linux.intel.com>
Cc: James Clark <james.clark@arm.com>
Cc: Atish Patra <atishp@atishpatra.org>
Cc: Mingwei Zhang <mizhang@google.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Palmer Dabbelt <palmer@rivosinc.com>
Link: https://lore.kernel.org/r/20241016062359.264929-8-namhyung@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 9d976acf08dd9b62ac773d3527a7ac09b7630184..f780e30aa259f545cce6b06a3cff1c185f38579d 100644 (file)
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2143,9 +2143,9 @@ static void evsel__detect_missing_pmu_features(struct evsel *evsel)
 
        /*
         * Must probe features in the order they were added to the
-        * perf_event_attr interface.  These are PMU specific limitation
-        * so we can detect with the given hardware event and stop on the
-        * first one succeeded.
+        * perf_event_attr interface.  These are kernel core limitation but
+        * specific to PMUs with branch stack.  So we can detect with the given
+        * hardware event and stop on the first one succeeded.
         */
 
        /* Please add new feature detection here. */
@@ -2409,6 +2409,25 @@ check:
        return false;
 }
 
+static bool evsel__handle_error_quirks(struct evsel *evsel, int error)
+{
+       /*
+        * AMD core PMU tries to forward events with precise_ip to IBS PMU
+        * implicitly.  But IBS PMU has more restrictions so it can fail with
+        * supported event attributes.  Let's forward it back to the core PMU
+        * by clearing precise_ip only if it's from precise_max (:P).
+        */
+       if ((error == -EINVAL || error == -ENOENT) && x86__is_amd_cpu() &&
+           evsel->core.attr.precise_ip && evsel->precise_max) {
+               evsel->core.attr.precise_ip = 0;
+               pr_debug2_peo("removing precise_ip on AMD\n");
+               display_attr(&evsel->core.attr);
+               return true;
+       }
+
+       return false;
+}
+
 static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
                struct perf_thread_map *threads,
                int start_cpu_map_idx, int end_cpu_map_idx)
@@ -2527,9 +2546,6 @@ retry_open:
        return 0;
 
 try_fallback:
-       if (evsel__precise_ip_fallback(evsel))
-               goto retry_open;
-
        if (evsel__ignore_missing_thread(evsel, perf_cpu_map__nr(cpus),
                                         idx, threads, thread, err)) {
                /* We just removed 1 thread, so lower the upper nthreads limit. */
@@ -2546,11 +2562,15 @@ try_fallback:
        if (err == -EMFILE && rlimit__increase_nofile(&set_rlimit))
                goto retry_open;
 
-       if (err != -EINVAL || idx > 0 || thread > 0)
-               goto out_close;
+       if (err == -EOPNOTSUPP && evsel__precise_ip_fallback(evsel))
+               goto retry_open;
 
-       if (evsel__detect_missing_features(evsel))
+       if (err == -EINVAL && evsel__detect_missing_features(evsel))
                goto fallback_missing_features;
+
+       if (evsel__handle_error_quirks(evsel, err))
+               goto retry_open;
+
 out_close:
        if (err)
                threads->err_thread = thread;