Commit 2b707029 authored Apr 09, 2025 by Namhyung Kim

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 c33aea44 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: c33aea44 ("perf tools: Fix precise_ip fallback logic")
Tested-by: Chun-Tse Shao <ctshao@google.com>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lore.kernel.org/r/20250410010252.402221-1-namhyung@kernel.org


Signed-off-by: Namhyung Kim <namhyung@kernel.org>

parent 1293dacb

tools/perf/util/evsel.c

+0 −22

Original line number	Diff line number	Diff line
		@@ -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;