linux-kernel - [PATCH] perf: arm_spe: Ensure trace is disabled when TRUNCATED flag is set

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Message-Id: <20251015-arm_spe_fix_truncated_flag-v1-1-555e328cba05@arm.com>
Date: Wed, 15 Oct 2025 19:23:37 +0100
From: Leo Yan <leo.yan@....com>
To: Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>, 
 Alexandru Elisei <alexandru.elisei@....com>, 
 James Clark <james.clark@...aro.org>
Cc: linux-arm-kernel@...ts.infradead.org, linux-perf-users@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Leo Yan <leo.yan@....com>
Subject: [PATCH] perf: arm_spe: Ensure trace is disabled when TRUNCATED
 flag is set

The TRUNCATED flag can be set in the following cases:

 1. When data loss is detected (PMBSR_EL1.DL == 0b1).
 2. When arm_spe_perf_aux_output_begin() fails to find a valid limit
    because it runs out of free space.

Currently, only the first case invokes irq_work_run() to execute the
event disable callback, while the second case does not.

Move the call to irq_work_run() later with checking the TRUNCATED flag,
so that both cases are handled and redundant calls are avoided.

Signed-off-by: Leo Yan <leo.yan@....com>
---
 drivers/perf/arm_spe_pmu.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c
index fa50645feddadbea5dc1e404f80f62cf5aa96fd4..05ba977f75d607a1d524f68694db9ea18a6ef20c 100644
--- a/drivers/perf/arm_spe_pmu.c
+++ b/drivers/perf/arm_spe_pmu.c
@@ -731,12 +731,6 @@ static irqreturn_t arm_spe_pmu_irq_handler(int irq, void *dev)
 	if (act == SPE_PMU_BUF_FAULT_ACT_SPURIOUS)
 		return IRQ_NONE;
 
-	/*
-	 * Ensure perf callbacks have completed, which may disable the
-	 * profiling buffer in response to a TRUNCATION flag.
-	 */
-	irq_work_run();
-
 	switch (act) {
 	case SPE_PMU_BUF_FAULT_ACT_FATAL:
 		/*
@@ -765,6 +759,15 @@ static irqreturn_t arm_spe_pmu_irq_handler(int irq, void *dev)
 		break;
 	}
 
+	/*
+	 * The TRUNCATED flag is set when data loss is detected by PMBSR_EL1.DL,
+	 * or arm_spe_perf_aux_output_begin() sets the flag if runs out of free
+	 * space. Ensure that all perf callbacks have completed for disabling
+	 * the profiling buffer.
+	 */
+	if (handle->aux_flags & PERF_AUX_FLAG_TRUNCATED)
+		irq_work_run();
+
 	/* The buffer pointers are now sane, so resume profiling. */
 	write_sysreg_s(0, SYS_PMBSR_EL1);
 	return IRQ_HANDLED;

---
base-commit: 1f4a222b0e334540343fbb5d3eac4584a6bfe180
change-id: 20251015-arm_spe_fix_truncated_flag-1a5b3620a3ab

Best regards,
-- 
Leo Yan <leo.yan@....com>