coresight: Use per-sink trace ID maps for Perf sessions

This will allow sessions with more than CORESIGHT_TRACE_IDS_MAX ETMs
as long as there are fewer than that many ETMs connected to each sink.

Each sink owns its own trace ID map, and any Perf session connecting to
that sink will allocate from it, even if the sink is currently in use by
other users. This is similar to the existing behavior where the dynamic
trace IDs are constant as long as there is any concurrent Perf session
active. It's not completely optimal because slightly more IDs will be
used than necessary, but the optimal solution involves tracking the PIDs
of each session and allocating ID maps based on the session owner. This
is difficult to do with the combination of per-thread and per-cpu modes
and some scheduling issues. The complexity of this isn't likely to worth
it because even with multiple users they'd just see a difference in the
ordering of ID allocations rather than hitting any limits (unless the
hardware does have too many ETMs connected to one sink).

Signed-off-by: James Clark <[email protected]>
Reviewed-by: Mike Leach <[email protected]>
Signed-off-by: James Clark <[email protected]>
Signed-off-by: Suzuki K Poulose <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: James-A-Clark

drivers/hwtracing/coresight/coresight-core.c

@@ -902,6 +902,7 @@ static void coresight_device_release(struct device *dev)
 	struct coresight_device *csdev = to_coresight_device(dev);
 
 	fwnode_handle_put(csdev->dev.fwnode);
+	free_percpu(csdev->perf_sink_id_map.cpu_map);
 	kfree(csdev);
 }
 
@@ -1159,6 +1160,15 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
 	csdev->dev.fwnode = fwnode_handle_get(dev_fwnode(desc->dev));
 	dev_set_name(&csdev->dev, "%s", desc->name);
 
+	if (csdev->type == CORESIGHT_DEV_TYPE_SINK ||
+	    csdev->type == CORESIGHT_DEV_TYPE_LINKSINK) {
+		csdev->perf_sink_id_map.cpu_map = alloc_percpu(atomic_t);
+		if (!csdev->perf_sink_id_map.cpu_map) {
+			kfree(csdev);
+			ret = -ENOMEM;
+			goto err_out;
+		}
+	}
 	/*
 	 * Make sure the device registration and the connection fixup
 	 * are synchronised, so that we don't see uninitialised devices

drivers/hwtracing/coresight/coresight-dummy.c

@@ -21,7 +21,8 @@ DEFINE_CORESIGHT_DEVLIST(source_devs, "dummy_source");
 DEFINE_CORESIGHT_DEVLIST(sink_devs, "dummy_sink");
 
 static int dummy_source_enable(struct coresight_device *csdev,
-			       struct perf_event *event, enum cs_mode mode)
+			       struct perf_event *event, enum cs_mode mode,
+			       __maybe_unused struct coresight_trace_id_map *id_map)
 {
 	if (!coresight_take_mode(csdev, mode))
 		return -EBUSY;

drivers/hwtracing/coresight/coresight-etm-perf.c

@@ -229,10 +229,13 @@ static void free_event_data(struct work_struct *work)
 		struct list_head **ppath;
 
 		ppath = etm_event_cpu_path_ptr(event_data, cpu);
-		if (!(IS_ERR_OR_NULL(*ppath)))
+		if (!(IS_ERR_OR_NULL(*ppath))) {
+			struct coresight_device *sink = coresight_get_sink(*ppath);
+
+			coresight_trace_id_put_cpu_id_map(cpu, &sink->perf_sink_id_map);
 			coresight_release_path(*ppath);
+		}
 		*ppath = NULL;
-		coresight_trace_id_put_cpu_id(cpu);
 	}
 
 	/* mark perf event as done for trace id allocator */
@@ -401,7 +404,7 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
 		}
 
 		/* ensure we can allocate a trace ID for this CPU */
-		trace_id = coresight_trace_id_get_cpu_id(cpu);
+		trace_id = coresight_trace_id_get_cpu_id_map(cpu, &sink->perf_sink_id_map);
 		if (!IS_VALID_CS_TRACE_ID(trace_id)) {
 			cpumask_clear_cpu(cpu, mask);
 			coresight_release_path(path);
@@ -495,7 +498,8 @@ static void etm_event_start(struct perf_event *event, int flags)
 		goto fail_end_stop;
 
 	/* Finally enable the tracer */
-	if (source_ops(csdev)->enable(csdev, event, CS_MODE_PERF))
+	if (source_ops(csdev)->enable(csdev, event, CS_MODE_PERF,
+				      &sink->perf_sink_id_map))
 		goto fail_disable_path;
 
 	/*
@@ -507,7 +511,8 @@ static void etm_event_start(struct perf_event *event, int flags)
 		hw_id = FIELD_PREP(CS_AUX_HW_ID_VERSION_MASK,
 				   CS_AUX_HW_ID_CURR_VERSION);
 		hw_id |= FIELD_PREP(CS_AUX_HW_ID_TRACE_ID_MASK,
-				    coresight_trace_id_read_cpu_id(cpu));
+				    coresight_trace_id_read_cpu_id_map(cpu,
+								       &sink->perf_sink_id_map));
 		perf_report_aux_output_id(event, hw_id);
 	}
 

drivers/hwtracing/coresight/coresight-etm3x-core.c

@@ -481,7 +481,8 @@ void etm_release_trace_id(struct etm_drvdata *drvdata)
 }
 
 static int etm_enable_perf(struct coresight_device *csdev,
-			   struct perf_event *event)
+			   struct perf_event *event,
+			   struct coresight_trace_id_map *id_map)
 {
 	struct etm_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 	int trace_id;
@@ -500,7 +501,7 @@ static int etm_enable_perf(struct coresight_device *csdev,
 	 * with perf locks - we know the ID cannot change until perf shuts down
 	 * the session
 	 */
-	trace_id = coresight_trace_id_read_cpu_id(drvdata->cpu);
+	trace_id = coresight_trace_id_read_cpu_id_map(drvdata->cpu, id_map);
 	if (!IS_VALID_CS_TRACE_ID(trace_id)) {
 		dev_err(&drvdata->csdev->dev, "Failed to set trace ID for %s on CPU%d\n",
 			dev_name(&drvdata->csdev->dev), drvdata->cpu);
@@ -553,7 +554,7 @@ static int etm_enable_sysfs(struct coresight_device *csdev)
 }
 
 static int etm_enable(struct coresight_device *csdev, struct perf_event *event,
-		      enum cs_mode mode)
+		      enum cs_mode mode, struct coresight_trace_id_map *id_map)
 {
 	int ret;
 	struct etm_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
@@ -568,7 +569,7 @@ static int etm_enable(struct coresight_device *csdev, struct perf_event *event,
 		ret = etm_enable_sysfs(csdev);
 		break;
 	case CS_MODE_PERF:
-		ret = etm_enable_perf(csdev, event);
+		ret = etm_enable_perf(csdev, event, id_map);
 		break;
 	default:
 		ret = -EINVAL;

drivers/hwtracing/coresight/coresight-etm4x-core.c

@@ -752,7 +752,8 @@ static int etm4_parse_event_config(struct coresight_device *csdev,
 }
 
 static int etm4_enable_perf(struct coresight_device *csdev,
-			    struct perf_event *event)
+			    struct perf_event *event,
+			    struct coresight_trace_id_map *id_map)
 {
 	int ret = 0, trace_id;
 	struct etmv4_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
@@ -775,7 +776,7 @@ static int etm4_enable_perf(struct coresight_device *csdev,
 	 * with perf locks - we know the ID cannot change until perf shuts down
 	 * the session
 	 */
-	trace_id = coresight_trace_id_read_cpu_id(drvdata->cpu);
+	trace_id = coresight_trace_id_read_cpu_id_map(drvdata->cpu, id_map);
 	if (!IS_VALID_CS_TRACE_ID(trace_id)) {
 		dev_err(&drvdata->csdev->dev, "Failed to set trace ID for %s on CPU%d\n",
 			dev_name(&drvdata->csdev->dev), drvdata->cpu);
@@ -837,7 +838,7 @@ static int etm4_enable_sysfs(struct coresight_device *csdev)
 }
 
 static int etm4_enable(struct coresight_device *csdev, struct perf_event *event,
-		       enum cs_mode mode)
+		       enum cs_mode mode, struct coresight_trace_id_map *id_map)
 {
 	int ret;
 
@@ -851,7 +852,7 @@ static int etm4_enable(struct coresight_device *csdev, struct perf_event *event,
 		ret = etm4_enable_sysfs(csdev);
 		break;
 	case CS_MODE_PERF:
-		ret = etm4_enable_perf(csdev, event);
+		ret = etm4_enable_perf(csdev, event, id_map);
 		break;
 	default:
 		ret = -EINVAL;

drivers/hwtracing/coresight/coresight-stm.c

@@ -194,7 +194,8 @@ static void stm_enable_hw(struct stm_drvdata *drvdata)
 }
 
 static int stm_enable(struct coresight_device *csdev, struct perf_event *event,
-		      enum cs_mode mode)
+		      enum cs_mode mode,
+		      __maybe_unused struct coresight_trace_id_map *trace_id)
 {
 	struct stm_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 

drivers/hwtracing/coresight/coresight-sysfs.c

@@ -9,6 +9,7 @@
 #include <linux/kernel.h>
 
 #include "coresight-priv.h"
+#include "coresight-trace-id.h"
 
 /*
  * Use IDR to map the hash of the source's device name
@@ -63,7 +64,7 @@ static int coresight_enable_source_sysfs(struct coresight_device *csdev,
 	 */
 	lockdep_assert_held(&coresight_mutex);
 	if (coresight_get_mode(csdev) != CS_MODE_SYSFS) {
-		ret = source_ops(csdev)->enable(csdev, data, mode);
+		ret = source_ops(csdev)->enable(csdev, data, mode, NULL);
 		if (ret)
 			return ret;
 	}

drivers/hwtracing/coresight/coresight-tpdm.c

@@ -439,7 +439,8 @@ static void __tpdm_enable(struct tpdm_drvdata *drvdata)
 }
 
 static int tpdm_enable(struct coresight_device *csdev, struct perf_event *event,
-		       enum cs_mode mode)
+		       enum cs_mode mode,
+		       __maybe_unused struct coresight_trace_id_map *id_map)
 {
 	struct tpdm_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 

include/linux/coresight.h

@@ -290,6 +290,7 @@ struct coresight_device {
 	bool sysfs_sink_activated;
 	struct dev_ext_attribute *ea;
 	struct coresight_device *def_sink;
+	struct coresight_trace_id_map perf_sink_id_map;
 	/* sysfs links between components */
 	int nr_links;
 	bool has_conns_grp;
@@ -384,7 +385,7 @@ struct coresight_ops_link {
 struct coresight_ops_source {
 	int (*cpu_id)(struct coresight_device *csdev);
 	int (*enable)(struct coresight_device *csdev, struct perf_event *event,
-		      enum cs_mode mode);
+		      enum cs_mode mode, struct coresight_trace_id_map *id_map);
 	void (*disable)(struct coresight_device *csdev,
 			struct perf_event *event);
 };