linux-kernel - [tip: perf/core] perf/x86/intel: Don't clear perf metrics overflow bit unconditionally

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Message-ID: <174489489952.31282.2734011160340897182.tip-bot2@tip-bot2>
Date: Thu, 17 Apr 2025 13:01:39 -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>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Ingo Molnar <mingo@...nel.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: Don't clear perf metrics overflow
 bit unconditionally

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

Commit-ID:     a5f5e1238f4ff919816f69e77d2537a48911767b
Gitweb:        https://git.kernel.org/tip/a5f5e1238f4ff919816f69e77d2537a48911767b
Author:        Dapeng Mi <dapeng1.mi@...ux.intel.com>
AuthorDate:    Tue, 15 Apr 2025 10:41:34 
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Thu, 17 Apr 2025 14:19:07 +02:00

perf/x86/intel: Don't clear perf metrics overflow bit unconditionally

The below code would always unconditionally clear other status bits like
perf metrics overflow bit once PEBS buffer overflows:

        status &= intel_ctrl | GLOBAL_STATUS_TRACE_TOPAPMI;

This is incorrect. Perf metrics overflow bit should be cleared only when
fixed counter 3 in PEBS counter group. Otherwise perf metrics overflow
could be missed to handle.

Closes: https://lore.kernel.org/all/20250225110012.GK31462@noisy.programming.kicks-ass.net/
Fixes: 7b2c05a15d29 ("perf/x86/intel: Generic support for hardware TopDown metrics")
Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>
Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/r/20250415104135.318169-1-dapeng1.mi@linux.intel.com
---
 arch/x86/events/intel/core.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 09d2d66..2b70a3a 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3049,7 +3049,6 @@ static int handle_pmi_common(struct pt_regs *regs, u64 status)
 	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
 	int bit;
 	int handled = 0;
-	u64 intel_ctrl = hybrid(cpuc->pmu, intel_ctrl);
 
 	inc_irq_stat(apic_perf_irqs);
 
@@ -3093,7 +3092,6 @@ static int handle_pmi_common(struct pt_regs *regs, u64 status)
 		handled++;
 		x86_pmu_handle_guest_pebs(regs, &data);
 		static_call(x86_pmu_drain_pebs)(regs, &data);
-		status &= intel_ctrl | GLOBAL_STATUS_TRACE_TOPAPMI;
 
 		/*
 		 * PMI throttle may be triggered, which stops the PEBS event.
@@ -3104,6 +3102,15 @@ static int handle_pmi_common(struct pt_regs *regs, u64 status)
 		 */
 		if (pebs_enabled != cpuc->pebs_enabled)
 			wrmsrl(MSR_IA32_PEBS_ENABLE, cpuc->pebs_enabled);
+
+		/*
+		 * Above PEBS handler (PEBS counters snapshotting) has updated fixed
+		 * counter 3 and perf metrics counts if they are in counter group,
+		 * unnecessary to update again.
+		 */
+		if (cpuc->events[INTEL_PMC_IDX_FIXED_SLOTS] &&
+		    is_pebs_counter_event_group(cpuc->events[INTEL_PMC_IDX_FIXED_SLOTS]))
+			status &= ~GLOBAL_STATUS_PERF_METRICS_OVF_BIT;
 	}
 
 	/*
@@ -3123,6 +3130,8 @@ static int handle_pmi_common(struct pt_regs *regs, u64 status)
 		static_call(intel_pmu_update_topdown_event)(NULL, NULL);
 	}
 
+	status &= hybrid(cpuc->pmu, intel_ctrl);
+
 	/*
 	 * Checkpointed counters can lead to 'spurious' PMIs because the
 	 * rollback caused by the PMI will have cleared the overflow status