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 <[e-mail]>
Reviewed-by: Jiri Olsa <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/Build

···
 perf-y += pmu.o
 perf-y += pmu-flex.o
 perf-y += pmu-bison.o
+perf-y += pmu-hybrid.o
 perf-y += trace-event-read.o
 perf-y += trace-event-info.o
 perf-y += trace-event-scripting.o

tools/perf/util/pmu-hybrid.c

···
+// 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;
+}

tools/perf/util/pmu-hybrid.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __PMU_HYBRID_H
+#define __PMU_HYBRID_H
+
+#include <linux/perf_event.h>
+#include <linux/compiler.h>
+#include <linux/list.h>
+#include <stdbool.h>
+#include "pmu.h"
+
+extern struct list_head perf_pmu__hybrid_pmus;
+
+#define perf_pmu__for_each_hybrid_pmu(pmu)	\
+	list_for_each_entry(pmu, &perf_pmu__hybrid_pmus, hybrid_list)
+
+bool perf_pmu__hybrid_mounted(const char *name);
+
+#endif /* __PMU_HYBRID_H */

tools/perf/util/pmu.c

···
 #include "string2.h"
 #include "strbuf.h"
 #include "fncache.h"
+#include "pmu-hybrid.h"
 
 struct perf_pmu perf_pmu__fake;
 
···
  */
 #define SYS_TEMPLATE_ID	"./bus/event_source/devices/%s/identifier"
 #define CPUS_TEMPLATE_UNCORE	"%s/bus/event_source/devices/%s/cpumask"
-#define CPUS_TEMPLATE_CPU	"%s/bus/event_source/devices/%s/cpus"
 
 static struct perf_cpu_map *pmu_cpumask(const char *name)
 {
···
 {
 	char path[PATH_MAX];
 	const char *sysfs;
+
+	if (perf_pmu__hybrid_mounted(name))
+		return false;
 
 	sysfs = sysfs__mountpoint();
 	snprintf(path, PATH_MAX, CPUS_TEMPLATE_UNCORE, sysfs, name);
···
 	pmu->is_uncore = pmu_is_uncore(name);
 	if (pmu->is_uncore)
 		pmu->id = pmu_id(name);
+	pmu->is_hybrid = perf_pmu__hybrid_mounted(name);
 	pmu->max_precise = pmu_max_precise(name);
 	pmu_add_cpu_aliases(&aliases, pmu);
 	pmu_add_sys_aliases(&aliases, pmu);
···
 	list_splice(&format, &pmu->format);
 	list_splice(&aliases, &pmu->aliases);
 	list_add_tail(&pmu->list, &pmus);
+
+	if (pmu->is_hybrid)
+		list_add_tail(&pmu->hybrid_list, &perf_pmu__hybrid_pmus);
 
 	pmu->default_config = perf_pmu__get_default_config(pmu);
 

tools/perf/util/pmu.h

···
 #include <linux/bitmap.h>
 #include <linux/compiler.h>
 #include <linux/perf_event.h>
+#include <linux/list.h>
 #include <stdbool.h>
 #include "parse-events.h"
 #include "pmu-events/pmu-events.h"
···
 
 #define PERF_PMU_FORMAT_BITS 64
 #define EVENT_SOURCE_DEVICE_PATH "/bus/event_source/devices/"
+#define CPUS_TEMPLATE_CPU	"%s/bus/event_source/devices/%s/cpus"
 
 struct perf_event_attr;
 
···
 	__u32 type;
 	bool selectable;
 	bool is_uncore;
+	bool is_hybrid;
 	bool auxtrace;
 	int max_precise;
 	struct perf_event_attr *default_config;
···
 	struct list_head aliases; /* HEAD struct perf_pmu_alias -> list */
 	struct list_head caps;    /* HEAD struct perf_pmu_caps -> list */
 	struct list_head list;    /* ELEM */
+	struct list_head hybrid_list;
 };
 
 extern struct perf_pmu perf_pmu__fake;