linux-kernel - [PATCH] perf tools: Remove evsel__handle_error

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Message-ID: <20250410010252.402221-1-namhyung@kernel.org>
Date: Wed,  9 Apr 2025 18:02:52 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Kan Liang <kan.liang@...ux.intel.com>
Cc: Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-perf-users@...r.kernel.org,
	Chun-Tse Shao <ctshao@...gle.com>,
	Ravi Bangoria <ravi.bangoria@....com>
Subject: [PATCH] perf tools: Remove evsel__handle_error_quirks()

The evsel__handle_error_quirks() is to fixup invalid event attributes on
some architecture based on the error code.  Currently it's only used for
AMD to disable precise_ip not to use IBS which has more restrictions.

But the commit c33aea446bf555ab changed call evsel__precise_ip_fallback
for any errors so there's no difference with the above function.  To
make matter worse, it caused a problem with branch stack on Zen3.

The IBS doesn't support branch stack so it should use a regular core
PMU event.  The default event is set precise_max and it starts with 3.
And evsel__precise_ip_fallback() tries with it and reduces the level one
by one.  At last it tries with 0 but it also failed on Zen3 since the
branch stack is not supported for the cycles event.

At this point, evsel__precise_ip_fallback() restores the original
precise_ip value (3) in the hope that it can succeed with other modifier
(like exclude_kernel).  Then evsel__handle_error_quirks() see it has
precise_ip != 0 and make it retry with 0.  This created an infinite
loop.

Before:

  $ perf record -b -vv |& grep removing
  removing precise_ip on AMD
  removing precise_ip on AMD
  removing precise_ip on AMD
  removing precise_ip on AMD
  removing precise_ip on AMD
  removing precise_ip on AMD
  removing precise_ip on AMD
  removing precise_ip on AMD
  removing precise_ip on AMD
  removing precise_ip on AMD
  removing precise_ip on AMD
  removing precise_ip on AMD
  ...

After:

  $ perf record -b true
  Error:
  Failure to open event 'cycles:P' on PMU 'cpu' which will be removed.
  Invalid event (cycles:P) in per-thread mode, enable system wide with '-a'.
  Error:
  Failure to open any events for recording.

Fixes: c33aea446bf555ab ("perf tools: Fix precise_ip fallback logic")
Cc: Ravi Bangoria <ravi.bangoria@....com>
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/util/evsel.c | 22 ----------------------
 1 file changed, 22 deletions(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 1974395492d7da5e..3c030da2e477c707 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2566,25 +2566,6 @@ static bool evsel__detect_missing_features(struct evsel *evsel, struct perf_cpu
 	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)
@@ -2730,9 +2711,6 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 	if (evsel__precise_ip_fallback(evsel))
 		goto retry_open;

-	if (evsel__handle_error_quirks(evsel, err))
-		goto retry_open;
-
 out_close:
 	if (err)
 		threads->err_thread = thread;
-- 
2.49.0.504.g3bcea36a83-goog