coresight: trbe: End the AUX handle on truncation

When we detect that there isn't enough space left to start a meaningful
session, we disable the TRBE, marking the buffer as TRUNCATED. But we delay
the notification to the perf layer by perf_aux_output_end() until the event
is scheduled out, triggered from the kernel perf layer. This will cause
significant black outs in the trace. Now that the CoreSight PMU layer can
handle a closed "AUX" handle properly, we can close the handle as soon as
we detect the case, allowing the userspace to collect and re-enable the
event.

Also, while in the IRQ handler, move the irq_work_run() after we have
updated the handle, to make sure the "TRUNCATED" flag causes the event to
be disabled as soon as possible.

Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20210923143919.2944311-5-suzuki.poulose@arm.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c
index 0a9106c..4174300 100644 (file)
--- a/drivers/hwtracing/coresight/coresight-trbe.c
+++ b/drivers/hwtracing/coresight/coresight-trbe.c
@@ -152,6 +152,7 @@ static void trbe_stop_and_truncate_event(struct perf_output_handle *handle)
         */
        trbe_drain_and_disable_local();
        perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
+       perf_aux_output_end(handle, 0);
        *this_cpu_ptr(buf->cpudata->drvdata->handle) = NULL;
 }
 
@@ -715,7 +716,7 @@ static void trbe_handle_spurious(struct perf_output_handle *handle)
        isb();
 }
 
-static void trbe_handle_overflow(struct perf_output_handle *handle)
+static int trbe_handle_overflow(struct perf_output_handle *handle)
 {
        struct perf_event *event = handle->event;
        struct trbe_buf *buf = etm_perf_sink_config(handle);
@@ -739,9 +740,10 @@ static void trbe_handle_overflow(struct perf_output_handle *handle)
                 */
                trbe_drain_and_disable_local();
                *this_cpu_ptr(buf->cpudata->drvdata->handle) = NULL;
-               return;
+               return -EINVAL;
        }
-       __arm_trbe_enable(buf, handle);
+
+       return __arm_trbe_enable(buf, handle);
 }
 
 static bool is_perf_trbe(struct perf_output_handle *handle)
@@ -772,6 +774,7 @@ static irqreturn_t arm_trbe_irq_handler(int irq, void *dev)
        struct perf_output_handle *handle = *handle_ptr;
        enum trbe_fault_action act;
        u64 status;
+       bool truncated = false;
 
        /* Reads to TRBSR_EL1 is fine when TRBE is active */
        status = read_sysreg_s(SYS_TRBSR_EL1);
@@ -796,24 +799,27 @@ static irqreturn_t arm_trbe_irq_handler(int irq, void *dev)
        if (!is_perf_trbe(handle))
                return IRQ_NONE;
 
-       /*
-        * Ensure perf callbacks have completed, which may disable
-        * the trace buffer in response to a TRUNCATION flag.
-        */
-       irq_work_run();
-
        act = trbe_get_fault_act(status);
        switch (act) {
        case TRBE_FAULT_ACT_WRAP:
-               trbe_handle_overflow(handle);
+               truncated = !!trbe_handle_overflow(handle);
                break;
        case TRBE_FAULT_ACT_SPURIOUS:
                trbe_handle_spurious(handle);
                break;
        case TRBE_FAULT_ACT_FATAL:
                trbe_stop_and_truncate_event(handle);
+               truncated = true;
                break;
        }
+
+       /*
+        * If the buffer was truncated, ensure perf callbacks
+        * have completed, which will disable the event.
+        */
+       if (truncated)
+               irq_work_run();
+
        return IRQ_HANDLED;
 }