samples/bpf: xdp_redirect_cpu: Set MAX_CPUS according to NR_CPUS

xdp_redirect_cpu is currently failing in bpf_prog_load_xattr()
allocating cpu_map map if CONFIG_NR_CPUS is less than 64 since
cpu_map_alloc() requires max_entries to be less than NR_CPUS.
Set cpu_map max_entries according to NR_CPUS in xdp_redirect_cpu_kern.c
and get currently running cpus in xdp_redirect_cpu_user.c

Signed-off-by: Lorenzo Bianconi <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>
Acked-by: Yonghong Song <[email protected]>
Link: https://lore.kernel.org/bpf/374472755001c260158c4e4b22f193bdd3c56fb7.1589300442.git.lorenzo@kernel.org

samples/bpf/xdp_redirect_cpu_kern.c

@@ -15,7 +15,7 @@
 #include <bpf/bpf_helpers.h>
 #include "hash_func01.h"
 
-#define MAX_CPUS 64 /* WARNING - sync with _user.c */
+#define MAX_CPUS NR_CPUS
 
 /* Special map type that can XDP_REDIRECT frames to another CPU */
 struct {

samples/bpf/xdp_redirect_cpu_user.c

@@ -13,6 +13,7 @@ static const char *__doc__ =
 #include <unistd.h>
 #include <locale.h>
 #include <sys/resource.h>
+#include <sys/sysinfo.h>
 #include <getopt.h>
 #include <net/if.h>
 #include <time.h>
@@ -24,8 +25,6 @@ static const char *__doc__ =
 #include <arpa/inet.h>
 #include <linux/if_link.h>
 
-#define MAX_CPUS 64 /* WARNING - sync with _kern.c */
-
 /* How many xdp_progs are defined in _kern.c */
 #define MAX_PROG 6
 
@@ -40,6 +39,7 @@ static char *ifname;
 static __u32 prog_id;
 
 static __u32 xdp_flags = XDP_FLAGS_UPDATE_IF_NOEXIST;
+static int n_cpus;
 static int cpu_map_fd;
 static int rx_cnt_map_fd;
 static int redirect_err_cnt_map_fd;
@@ -170,7 +170,7 @@ struct stats_record {
 	struct record redir_err;
 	struct record kthread;
 	struct record exception;
-	struct record enq[MAX_CPUS];
+	struct record enq[];
 };
 
 static bool map_collect_percpu(int fd, __u32 key, struct record *rec)
@@ -225,10 +225,11 @@ static struct datarec *alloc_record_per_cpu(void)
 static struct stats_record *alloc_stats_record(void)
 {
 	struct stats_record *rec;
-	int i;
+	int i, size;
 
-	rec = malloc(sizeof(*rec));
-	memset(rec, 0, sizeof(*rec));
+	size = sizeof(*rec) + n_cpus * sizeof(struct record);
+	rec = malloc(size);
+	memset(rec, 0, size);
 	if (!rec) {
 		fprintf(stderr, "Mem alloc error\n");
 		exit(EXIT_FAIL_MEM);
@@ -237,7 +238,7 @@ static struct stats_record *alloc_stats_record(void)
 	rec->redir_err.cpu = alloc_record_per_cpu();
 	rec->kthread.cpu   = alloc_record_per_cpu();
 	rec->exception.cpu = alloc_record_per_cpu();
-	for (i = 0; i < MAX_CPUS; i++)
+	for (i = 0; i < n_cpus; i++)
 		rec->enq[i].cpu = alloc_record_per_cpu();
 
 	return rec;
@@ -247,7 +248,7 @@ static void free_stats_record(struct stats_record *r)
 {
 	int i;
 
-	for (i = 0; i < MAX_CPUS; i++)
+	for (i = 0; i < n_cpus; i++)
 		free(r->enq[i].cpu);
 	free(r->exception.cpu);
 	free(r->kthread.cpu);
@@ -350,7 +351,7 @@ static void stats_print(struct stats_record *stats_rec,
 	}
 
 	/* cpumap enqueue stats */
-	for (to_cpu = 0; to_cpu < MAX_CPUS; to_cpu++) {
+	for (to_cpu = 0; to_cpu < n_cpus; to_cpu++) {
 		char *fmt = "%-15s %3d:%-3d %'-14.0f %'-11.0f %'-10.2f %s\n";
 		char *fm2 = "%-15s %3s:%-3d %'-14.0f %'-11.0f %'-10.2f %s\n";
 		char *errstr = "";
@@ -475,7 +476,7 @@ static void stats_collect(struct stats_record *rec)
 	map_collect_percpu(fd, 1, &rec->redir_err);
 
 	fd = cpumap_enqueue_cnt_map_fd;
-	for (i = 0; i < MAX_CPUS; i++)
+	for (i = 0; i < n_cpus; i++)
 		map_collect_percpu(fd, i, &rec->enq[i]);
 
 	fd = cpumap_kthread_cnt_map_fd;
@@ -549,10 +550,10 @@ static int create_cpu_entry(__u32 cpu, __u32 queue_size,
  */
 static void mark_cpus_unavailable(void)
 {
-	__u32 invalid_cpu = MAX_CPUS;
+	__u32 invalid_cpu = n_cpus;
 	int ret, i;
 
-	for (i = 0; i < MAX_CPUS; i++) {
+	for (i = 0; i < n_cpus; i++) {
 		ret = bpf_map_update_elem(cpus_available_map_fd, &i,
 					  &invalid_cpu, 0);
 		if (ret) {
@@ -688,6 +689,8 @@ int main(int argc, char **argv)
 	int prog_fd;
 	__u32 qsize;
 
+	n_cpus = get_nprocs_conf();
+
 	/* Notice: choosing he queue size is very important with the
 	 * ixgbe driver, because it's driver page recycling trick is
 	 * dependend on pages being returned quickly.  The number of
@@ -757,7 +760,7 @@ int main(int argc, char **argv)
 		case 'c':
 			/* Add multiple CPUs */
 			add_cpu = strtoul(optarg, NULL, 0);
-			if (add_cpu >= MAX_CPUS) {
+			if (add_cpu >= n_cpus) {
 				fprintf(stderr,
 				"--cpu nr too large for cpumap err(%d):%s\n",
 					errno, strerror(errno));