linux-kernel - [PATCH] perf/x86/intel: Correct wrong 'or' operation for pmu capabilities

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Date:   Tue, 21 Nov 2023 09:46:28 +0800
From:   Dapeng Mi <dapeng1.mi@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Kan Liang <kan.liang@...ux.intel.com>
Cc:     linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Dapeng Mi <dapeng1.mi@...el.com>,
        Dapeng Mi <dapeng1.mi@...ux.intel.com>, stable@...r.kernel.org
Subject: [PATCH] perf/x86/intel: Correct wrong 'or' operation for pmu capabilities

When running perf-stat command on Intel hybrid platform, perf-stat
reports the following errors.

sudo taskset -c 7 ./perf stat -vvvv -e cpu_atom/instructions/ sleep 1

Opening: cpu/cycles/:HG
------------------------------------------------------------
perf_event_attr:
  type                             0 (PERF_TYPE_HARDWARE)
  config                           0xa00000000
  disabled                         1
------------------------------------------------------------
sys_perf_event_open: pid 0  cpu -1  group_fd -1  flags 0x8
sys_perf_event_open failed, error -16

 Performance counter stats for 'sleep 1':

     <not counted>      cpu_atom/instructions/

It looks the cpu_atom/instructions/ event can't be enabled on atom pmu
even the process is pinned on atom core. The investigation shows that
exclusive_event_init() helper always returns -EBUSY error in the perf
event creation. That's strange since the atom pmu should not be a
exclusive PMU.

Further investigation shows the issue is introduced by commit 97588df87b56
("perf/x86/intel: Add common intel_pmu_init_hybrid()"). The commit
originally intents to clear the bit PERF_PMU_CAP_AUX_OUTPUT from pmu
capabilities if intel_cap.pebs_output_pt_available is not set, but it
incorrectly uses 'or' operation and leads to all pmu capabilities bits
are set to 1 except bit PERF_PMU_CAP_AUX_OUTPUT.

Testing this fix on Intel hybrid platforms, the observed issues
disappear.

Fixes: 97588df87b56 ("perf/x86/intel: Add common intel_pmu_init_hybrid()")
Cc: stable@...r.kernel.org
Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
---
 arch/x86/events/intel/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index a08f794a0e79..ce1c777227b4 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -4660,7 +4660,7 @@ static void intel_pmu_check_hybrid_pmus(struct x86_hybrid_pmu *pmu)
 	if (pmu->intel_cap.pebs_output_pt_available)
 		pmu->pmu.capabilities |= PERF_PMU_CAP_AUX_OUTPUT;
 	else
-		pmu->pmu.capabilities |= ~PERF_PMU_CAP_AUX_OUTPUT;
+		pmu->pmu.capabilities &= ~PERF_PMU_CAP_AUX_OUTPUT;

 	intel_pmu_check_event_constraints(pmu->event_constraints,
 					  pmu->num_counters,

base-commit: b85ea95d086471afb4ad062012a4d73cd328fa86
-- 
2.34.1