[PATCH v2 1/2] perf: arm_spe: Correct setting the PERF_HES_STOPPED flag

[Leo Yan]

In arm_spe_perf_aux_output_begin(), if the calculation of limit fails
and arm_spe_pmu_next_off() returns zero, the driver misses to set the
PERF_HES_STOPPED flag for the event.  As a result, hwc->state does not
reflect the latest state, which can mislead subsequent operations.

Validate the limit when exiting the function: if the limit is 0,
that tracing is disabled, set the PERF_HES_STOPPED flag accordingly.

Fixes: d5d9696b0380 ("drivers/perf: Add support for ARMv8.2 Statistical Profiling Extension")
Signed-off-by: Leo Yan <leo.yan at arm.com>
---
 drivers/perf/arm_spe_pmu.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c
index fa50645feddadbea5dc1e404f80f62cf5aa96fd4..fc8f908c2c3a270f2d1ae574c2badb1fbcf51484 100644
--- a/drivers/perf/arm_spe_pmu.c
+++ b/drivers/perf/arm_spe_pmu.c
@@ -597,7 +597,6 @@ static void arm_spe_perf_aux_output_begin(struct perf_output_handle *handle,
 	/* Start a new aux session */
 	buf = perf_aux_output_begin(handle, event);
 	if (!buf) {
-		event->hw.state |= PERF_HES_STOPPED;
 		/*
 		 * We still need to clear the limit pointer, since the
 		 * profiler might only be disabled by virtue of a fault.
@@ -608,15 +607,19 @@ static void arm_spe_perf_aux_output_begin(struct perf_output_handle *handle,
 
 	limit = buf->snapshot ? arm_spe_pmu_next_snapshot_off(handle)
 			      : arm_spe_pmu_next_off(handle);
-	if (limit)
-		limit |= PMBLIMITR_EL1_E;
+	if (!limit)
+		goto out_write_limit;
 
 	limit += (u64)buf->base;
+	limit |= PMBLIMITR_EL1_E;
 	base = (u64)buf->base + PERF_IDX2OFF(handle->head, buf);
 	write_sysreg_s(base, SYS_PMBPTR_EL1);
 
 out_write_limit:
 	write_sysreg_s(limit, SYS_PMBLIMITR_EL1);
+
+	if (!limit)
+		event->hw.state |= PERF_HES_STOPPED;
 }
 
 static void arm_spe_perf_aux_output_end(struct perf_output_handle *handle)

-- 
2.34.1