linux-kernel - [tip: perf/urgent] perf/x86/intel: Correct incorrect 'or' operation for PMU capabilities

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Message-ID: <170057084740.398.2179310454610572769.tip-bot2@tip-bot2>
Date:   Tue, 21 Nov 2023 12:47:27 -0000
From:   "tip-bot2 for Dapeng Mi" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Dapeng Mi <dapeng1.mi@...ux.intel.com>,
        Ingo Molnar <mingo@...nel.org>, stable@...r.kernel.org,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: perf/urgent] perf/x86/intel: Correct incorrect 'or' operation
 for PMU capabilities

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

Commit-ID:     e8df9d9f4209c04161321d8c12640ae560f65939
Gitweb:        https://git.kernel.org/tip/e8df9d9f4209c04161321d8c12640ae560f65939
Author:        Dapeng Mi <dapeng1.mi@...ux.intel.com>
AuthorDate:    Tue, 21 Nov 2023 09:46:28 +08:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Tue, 21 Nov 2023 13:44:36 +01:00

perf/x86/intel: Correct incorrect '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 when the process is pinned on atom core. 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 an
exclusive PMU.

Further investigation shows the issue was 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()")
Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/r/20231121014628.729989-1-dapeng1.mi@linux.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 a08f794..ce1c777 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,