diff --git a/tools/tracing/rtla/src/common.c b/tools/tracing/rtla/src/common.c
index 20fae1f19cac..2a5333270e03 100644
--- a/tools/tracing/rtla/src/common.c
+++ b/tools/tracing/rtla/src/common.c
@@ -62,11 +62,22 @@ static void unset_signals(struct common_params *params)
 int
 common_apply_config(struct osnoise_tool *tool, struct common_params *params)
 {
-	int retval, i;
+	int retval, i, tracer_cpus;
 
 	if (!params->sleep_time)
 		params->sleep_time = 1;
 
+	tracer_cpus = osnoise_get_cpu_count();
+	if (tracer_cpus < 0) {
+		err_msg("Failed to get tracer cpu count from osnoise/cpus\n");
+		goto out_err;
+	}
+	if (tracer_cpus != nr_cpus) {
+		err_msg("Kernel reports %d cpus but rtla sees %d\n",
+			tracer_cpus, nr_cpus);
+		goto out_err;
+	}
+
 	retval = osnoise_set_cpus(tool->context, params->cpus ? params->cpus : "all");
 	if (retval) {
 		err_msg("Failed to apply CPUs config\n");
diff --git a/tools/tracing/rtla/src/common.h b/tools/tracing/rtla/src/common.h
index 051d56182276..a7a9063c302b 100644
--- a/tools/tracing/rtla/src/common.h
+++ b/tools/tracing/rtla/src/common.h
@@ -168,6 +168,7 @@ should_continue_tracing(const struct common_params *params)
 int
 common_threshold_handler(const struct osnoise_tool *tool);
 
+int osnoise_get_cpu_count(void);
 int osnoise_set_cpus(struct osnoise_context *context, char *cpus);
 void osnoise_restore_cpus(struct osnoise_context *context);
 
diff --git a/tools/tracing/rtla/src/osnoise.c b/tools/tracing/rtla/src/osnoise.c
index b9bcbf9ee430..5a746bc11f03 100644
--- a/tools/tracing/rtla/src/osnoise.c
+++ b/tools/tracing/rtla/src/osnoise.c
@@ -124,6 +124,50 @@ void osnoise_put_cpus(struct osnoise_context *context)
 	context->orig_cpus = NULL;
 }
 
+/*
+ * osnoise_get_cpu_count - get the number of CPUs as seen by the osnoise tracer
+ *
+ * Write "all" to osnoise/cpus and read back the real kernel-side list
+ * of all possible cpus. Restore the original value afterwards.
+ *
+ * Returns the number of CPUs, or -1 on error.
+ */
+int osnoise_get_cpu_count(void)
+{
+	char *orig, *readback;
+	int max_cpu;
+
+	orig = tracefs_instance_file_read(NULL, "osnoise/cpus", NULL);
+	if (!orig)
+		return -1;
+
+	if (tracefs_instance_file_write(NULL, "osnoise/cpus", "all\n") < 0) {
+		free(orig);
+		return -1;
+	}
+
+	readback = tracefs_instance_file_read(NULL, "osnoise/cpus", NULL);
+	if (!readback) {
+		tracefs_instance_file_write(NULL, "osnoise/cpus", orig);
+		free(orig);
+		return -1;
+	}
+
+	max_cpu = get_max_cpu_from_list(readback);
+	free(readback);
+
+	if (tracefs_instance_file_write(NULL, "osnoise/cpus", orig) < 0) {
+		free(orig);
+		return -1;
+	}
+	free(orig);
+
+	if (max_cpu < 0)
+		return -1;
+
+	return max_cpu + 1;
+}
+
 /*
  * osnoise_read_ll_config - read a long long value from a config
  *
diff --git a/tools/tracing/rtla/src/utils.c b/tools/tracing/rtla/src/utils.c
index d65de511be9e..5d91c9151aa4 100644
--- a/tools/tracing/rtla/src/utils.c
+++ b/tools/tracing/rtla/src/utils.c
@@ -161,6 +161,22 @@ static int max_cpu_callback(int i, void *data)
 	return 0;
 }
 
+/*
+ * get_max_cpu_from_list - get the maximum CPU in a CPU list
+ *
+ * Returns maximum CPU number, or -1 on error
+ */
+int get_max_cpu_from_list(const char *cpu_list)
+{
+	int max_cpu = -1;
+
+	if (cpu_list_iterate(cpu_list, max_cpu_callback, &max_cpu) < 0)
+		return -1;
+
+	return max_cpu;
+}
+
+
 static int tmp_cpu_set_callback(int i, void *data)
 {
 	bool *cpu_set = data;
diff --git a/tools/tracing/rtla/src/utils.h b/tools/tracing/rtla/src/utils.h
index 2579e7fa08be..44b450645ffb 100644
--- a/tools/tracing/rtla/src/utils.h
+++ b/tools/tracing/rtla/src/utils.h
@@ -50,6 +50,7 @@ long parse_seconds_duration(char *val);
 void get_duration(time_t start_time, char *output, int output_size);
 
 int cpu_list_iterate(const char *cpu_list, int (*callback)(int, void *), void *data);
+int get_max_cpu_from_list(const char *cpu_list);
 int get_possible_cpus(void);
 
 long long get_llong_from_str(char *start);