From af954f76eea56453713ae657f6812d4063f9bc57 Mon Sep 17 00:00:00 2001 From: Namhyung Kim Date: Tue, 15 Oct 2024 23:23:57 -0700 Subject: [PATCH] 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 Reviewed-by: Ravi Bangoria Acked-by: Kan Liang Cc: James Clark Cc: Atish Patra Cc: Mingwei Zhang Cc: Kajol Jain Cc: Thomas Richter Cc: Palmer Dabbelt Link: https://lore.kernel.org/r/20241016062359.264929-8-namhyung@kernel.org Signed-off-by: Namhyung Kim --- tools/perf/util/evsel.c | 38 +++++++++++++++++++++++++++++--------- 1 file changed, 29 insertions(+), 9 deletions(-) diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c index 9d976acf08dd9..f780e30aa259f 100644 --- 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 @@ static bool evsel__detect_missing_features(struct evsel *evsel) 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 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus, 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 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus, 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;