linux-kernel - [tip: perf/core] perf/x86/intel: Avoid disable PMU if !cpuc->enabled in sample read

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Message-ID: <173858689602.10177.10533539572800988439.tip-bot2@tip-bot2>
Date: Mon, 03 Feb 2025 12:48:16 -0000
From: "tip-bot2 for Kan Liang" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Kan Liang <kan.liang@...ux.intel.com>, stable@...r.kernel.org, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: perf/core] perf/x86/intel: Avoid disable PMU if !cpuc->enabled
 in sample read

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

Commit-ID:     5c32ae8ac8936b992fc0069c6438df932a753325
Gitweb:        https://git.kernel.org/tip/5c32ae8ac8936b992fc0069c6438df932a753325
Author:        Kan Liang <kan.liang@...ux.intel.com>
AuthorDate:    Tue, 21 Jan 2025 07:23:01 -08:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 03 Feb 2025 11:46:07 +01:00

perf/x86/intel: Avoid disable PMU if !cpuc->enabled in sample read

The WARN_ON(this_cpu_read(cpu_hw_events.enabled)) in the
intel_pmu_save_and_restart_reload() is triggered, when sampling read
topdown events.

In a NMI handler, the cpu_hw_events.enabled is set and used to indicate
the status of core PMU. The generic pmu->pmu_disable_count, updated in
the perf_pmu_disable/enable pair, is not touched.
However, the perf_pmu_disable/enable pair is invoked when sampling read
in a NMI handler. The cpuc->enabled is mistakenly set by the
perf_pmu_enable().

Avoid disabling PMU if the core PMU is already disabled.
Merge the logic together.

Fixes: 7b2c05a15d29 ("perf/x86/intel: Generic support for hardware TopDown metrics")
Suggested-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: stable@...r.kernel.org
Link: https://lkml.kernel.org/r/20250121152303.3128733-2-kan.liang@linux.intel.com
---
 arch/x86/events/intel/core.c | 41 +++++++++++++++++++----------------
 arch/x86/events/intel/ds.c   | 11 +---------
 arch/x86/events/perf_event.h |  2 +-
 3 files changed, 25 insertions(+), 29 deletions(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 2acea83..1ccc961 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -2785,28 +2785,33 @@ static u64 icl_update_topdown_event(struct perf_event *event)
 
 DEFINE_STATIC_CALL(intel_pmu_update_topdown_event, x86_perf_event_update);
 
-static void intel_pmu_read_topdown_event(struct perf_event *event)
+static void intel_pmu_read_event(struct perf_event *event)
 {
-	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+	if (event->hw.flags & (PERF_X86_EVENT_AUTO_RELOAD | PERF_X86_EVENT_TOPDOWN)) {
+		struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+		bool pmu_enabled = cpuc->enabled;
 
-	/* Only need to call update_topdown_event() once for group read. */
-	if ((cpuc->txn_flags & PERF_PMU_TXN_READ) &&
-	    !is_slots_event(event))
-		return;
+		/* Only need to call update_topdown_event() once for group read. */
+		if (is_metric_event(event) && (cpuc->txn_flags & PERF_PMU_TXN_READ))
+			return;
 
-	perf_pmu_disable(event->pmu);
-	static_call(intel_pmu_update_topdown_event)(event);
-	perf_pmu_enable(event->pmu);
-}
+		cpuc->enabled = 0;
+		if (pmu_enabled)
+			intel_pmu_disable_all();
 
-static void intel_pmu_read_event(struct perf_event *event)
-{
-	if (event->hw.flags & PERF_X86_EVENT_AUTO_RELOAD)
-		intel_pmu_auto_reload_read(event);
-	else if (is_topdown_count(event))
-		intel_pmu_read_topdown_event(event);
-	else
-		x86_perf_event_update(event);
+		if (is_topdown_event(event))
+			static_call(intel_pmu_update_topdown_event)(event);
+		else
+			intel_pmu_drain_pebs_buffer();
+
+		cpuc->enabled = pmu_enabled;
+		if (pmu_enabled)
+			intel_pmu_enable_all(0);
+
+		return;
+	}
+
+	x86_perf_event_update(event);
 }
 
 static void intel_pmu_enable_fixed(struct perf_event *event)
diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 322963b..eb14b46 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -953,7 +953,7 @@ unlock:
 	return 1;
 }
 
-static inline void intel_pmu_drain_pebs_buffer(void)
+void intel_pmu_drain_pebs_buffer(void)
 {
 	struct perf_sample_data data;
 
@@ -2094,15 +2094,6 @@ get_next_pebs_record_by_bit(void *base, void *top, int bit)
 	return NULL;
 }
 
-void intel_pmu_auto_reload_read(struct perf_event *event)
-{
-	WARN_ON(!(event->hw.flags & PERF_X86_EVENT_AUTO_RELOAD));
-
-	perf_pmu_disable(event->pmu);
-	intel_pmu_drain_pebs_buffer();
-	perf_pmu_enable(event->pmu);
-}
-
 /*
  * Special variant of intel_pmu_save_and_restart() for auto-reload.
  */
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index 084e919..536a112 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -1644,7 +1644,7 @@ void intel_pmu_pebs_disable_all(void);
 
 void intel_pmu_pebs_sched_task(struct perf_event_pmu_context *pmu_ctx, bool sched_in);
 
-void intel_pmu_auto_reload_read(struct perf_event *event);
+void intel_pmu_drain_pebs_buffer(void);
 
 void intel_pmu_store_pebs_lbrs(struct lbr_entry *lbr);