linux-kernel - [tip: perf/urgent] perf/x86: Fix non-sampling (counting) events on certain x86 platforms

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Message-ID: <174551892205.31282.8764078433432267645.tip-bot2@tip-bot2>
Date: Thu, 24 Apr 2025 18:22:01 -0000
From: "tip-bot2 for Luo Gengkun" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Luo Gengkun <luogengkun@...weicloud.com>, Ingo Molnar <mingo@...nel.org>,
 Kan Liang <kan.liang@...ux.intel.com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Arnaldo Carvalho de Melo <acme@...hat.com>, Jiri Olsa <jolsa@...hat.com>,
 Mark Rutland <mark.rutland@....com>, Namhyung Kim <namhyung@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>, Ravi Bangoria <ravi.bangoria@....com>,
 x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: perf/urgent] perf/x86: Fix non-sampling (counting) events on
 certain x86 platforms

The following commit has been merged into the perf/urgent branch of tip:

Commit-ID:     1a97fea9db9e9b9c4839d4232dde9f505ff5b4cc
Gitweb:        https://git.kernel.org/tip/1a97fea9db9e9b9c4839d4232dde9f505ff5b4cc
Author:        Luo Gengkun <luogengkun@...weicloud.com>
AuthorDate:    Wed, 23 Apr 2025 06:47:24 
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Thu, 24 Apr 2025 20:15:04 +02:00

perf/x86: Fix non-sampling (counting) events on certain x86 platforms

Perf doesn't work at perf stat for hardware events on certain x86 platforms:

 $perf stat -- sleep 1
 Performance counter stats for 'sleep 1':
             16.44 msec task-clock                       #    0.016 CPUs utilized
                 2      context-switches                 #  121.691 /sec
                 0      cpu-migrations                   #    0.000 /sec
                54      page-faults                      #    3.286 K/sec
   <not supported>	cycles
   <not supported>	instructions
   <not supported>	branches
   <not supported>	branch-misses

The reason is that the check in x86_pmu_hw_config() for sampling events is
unexpectedly applied to counting events as well.

It should only impact x86 platforms with limit_period used for non-PEBS
events. For Intel platforms, it should only impact some older platforms,
e.g., HSW, BDW and NHM.

Fixes: 88ec7eedbbd2 ("perf/x86: Fix low freqency setting issue")
Signed-off-by: Luo Gengkun <luogengkun@...weicloud.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ravi Bangoria <ravi.bangoria@....com>
Link: https://lore.kernel.org/r/20250423064724.3716211-1-luogengkun@huaweicloud.com
---
 arch/x86/events/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 6866cc5..3a4f031 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -629,7 +629,7 @@ int x86_pmu_hw_config(struct perf_event *event)
 	if (event->attr.type == event->pmu->type)
 		event->hw.config |= x86_pmu_get_event_config(event);
 
-	if (!event->attr.freq && x86_pmu.limit_period) {
+	if (is_sampling_event(event) && !event->attr.freq && x86_pmu.limit_period) {
 		s64 left = event->attr.sample_period;
 		x86_pmu.limit_period(event, &left);
 		if (left > event->attr.sample_period)