6.14-stable review patch. If anyone has any objections, please let me know.
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From: Namhyung Kim namhyung@kernel.org
[ Upstream commit 2b70702917337a8d6d07f03eed961e0119091647 ]
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") 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 Signed-off-by: Sasha Levin sashal@kernel.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 9cd78cdee6282..c99eb9ff17ed6 100644 --- a/tools/perf/util/evsel.c +++ b/tools/perf/util/evsel.c @@ -2556,25 +2556,6 @@ 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) @@ -2720,9 +2701,6 @@ 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;