perf pmu: Save detected hybrid pmus to a global pmu list

We identify the cpu_core pmu and cpu_atom pmu by explicitly
checking following files:

For cpu_core, checks:
"/sys/bus/event_source/devices/cpu_core/cpus"

For cpu_atom, checks:
"/sys/bus/event_source/devices/cpu_atom/cpus"

If the 'cpus' file exists and it has data, the pmu exists.

But in order not to hardcode the "cpu_core" and "cpu_atom",
and make the code in a generic way.

So if the path "/sys/bus/event_source/devices/cpu_xxx/cpus" exists, the
hybrid pmu exists. All the detected hybrid pmus are linked to a global
list 'perf_pmu__hybrid_pmus' and then next we just need to iterate the
list to get all hybrid pmu by using perf_pmu__for_each_hybrid_pmu.

Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210427070139.25256-6-yao.jin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 49 insertions, 0 deletions

diff --git a/tools/perf/util/pmu-hybrid.c b/tools/perf/util/pmu-hybrid.c
new file mode 100644
index 000000000000..8ed0e6e1776d
--- /dev/null
+++ b/tools/perf/util/pmu-hybrid.c
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/list.h>
+#include <linux/compiler.h>
+#include <linux/string.h>
+#include <linux/zalloc.h>
+#include <sys/types.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include <stdarg.h>
+#include <locale.h>
+#include <api/fs/fs.h>
+#include "fncache.h"
+#include "pmu-hybrid.h"
+
+LIST_HEAD(perf_pmu__hybrid_pmus);
+
+bool perf_pmu__hybrid_mounted(const char *name)
+{
+	char path[PATH_MAX];
+	const char *sysfs;
+	FILE *file;
+	int n, cpu;
+
+	if (strncmp(name, "cpu_", 4))
+		return false;
+
+	sysfs = sysfs__mountpoint();
+	if (!sysfs)
+		return false;
+
+	snprintf(path, PATH_MAX, CPUS_TEMPLATE_CPU, sysfs, name);
+	if (!file_available(path))
+		return false;
+
+	file = fopen(path, "r");
+	if (!file)
+		return false;
+
+	n = fscanf(file, "%u", &cpu);
+	fclose(file);
+	if (n <= 0)
+		return false;
+
+	return true;
+}