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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2025 Andrea Righi <arighi@nvidia.com>
*/
#define _GNU_SOURCE
#include <bpf/bpf.h>
#include <limits.h>
#include <sched.h>
#include <scx/common.h>
#include <sys/wait.h>
#include <unistd.h>
#include "allowed_cpus.bpf.skel.h"
#include "scx_test.h"
static enum scx_test_status setup(void **ctx)
{
struct allowed_cpus *skel;
skel = allowed_cpus__open();
SCX_FAIL_IF(!skel, "Failed to open");
SCX_ENUM_INIT(skel);
SCX_FAIL_IF(allowed_cpus__load(skel), "Failed to load skel");
*ctx = skel;
return SCX_TEST_PASS;
}
static int test_select_cpu_from_user(const struct allowed_cpus *skel,
const char *name, int custom_cpu,
bool expect_busy)
{
int fd, ret;
__s32 cpu;
__u64 args[] = { getpid(), (__u64)(__s64)custom_cpu };
LIBBPF_OPTS(bpf_test_run_opts, attr,
.ctx_in = args,
.ctx_size_in = sizeof(args),
);
fd = bpf_program__fd(skel->progs.select_cpu_from_user);
if (fd < 0)
return fd;
ret = bpf_prog_test_run_opts(fd, &attr);
if (ret < 0)
return ret;
/* test_run returns the signed BPF result through an unsigned field. */
cpu = (__s32)attr.retval;
if ((expect_busy && cpu != -EBUSY) ||
(!expect_busy && cpu != -EBUSY && cpu != custom_cpu)) {
SCX_ERR("%s: unexpected CPU selection result %d", name, cpu);
return -EINVAL;
}
return 0;
}
/* Grow until the mask covers the kernel's CPU range, including offline CPUs. */
static int alloc_affinity(cpu_set_t **mask, size_t *size)
{
int nr_cpus = CPU_SETSIZE;
cpu_set_t *cpus;
int err;
for (;;) {
*size = CPU_ALLOC_SIZE(nr_cpus);
cpus = CPU_ALLOC(nr_cpus);
if (!cpus)
return -ENOMEM;
CPU_ZERO_S(*size, cpus);
if (!sched_getaffinity(0, *size, cpus)) {
*mask = cpus;
return nr_cpus;
}
err = errno;
CPU_FREE(cpus);
if (err != EINVAL)
return -err;
if (nr_cpus > INT_MAX / 2)
return -EOVERFLOW;
nr_cpus *= 2;
}
}
static enum scx_test_status run(void *ctx)
{
struct allowed_cpus *skel = ctx;
enum scx_test_status status = SCX_TEST_FAIL;
cpu_set_t *original = NULL, *pinned = NULL;
bool affinity_changed = false;
size_t size;
int first = -1, second = -1, cpu, nr_cpus;
struct bpf_link *link = NULL;
nr_cpus = alloc_affinity(&original, &size);
if (nr_cpus < 0) {
SCX_ERR("Failed to get affinity (%d)", -nr_cpus);
goto out;
}
pinned = CPU_ALLOC(nr_cpus);
if (!pinned) {
SCX_ERR("Failed to allocate affinity mask");
goto out;
}
for (cpu = 0; cpu < nr_cpus; cpu++) {
if (!CPU_ISSET_S(cpu, size, original))
continue;
if (first < 0) {
first = cpu;
} else {
second = cpu;
break;
}
}
if (first < 0) {
SCX_ERR("No CPU in affinity mask");
goto out;
}
link = bpf_map__attach_struct_ops(skel->maps.allowed_cpus_ops);
if (!link) {
SCX_ERR("Failed to attach scheduler");
goto out;
}
if (test_select_cpu_from_user(skel, "empty mask", -1, true))
goto out;
/* A legal candidate may be busy; selection need not succeed. */
if (test_select_cpu_from_user(skel, "legal candidate", first, false))
goto out;
if (second >= 0) {
CPU_ZERO_S(size, pinned);
CPU_SET_S(first, size, pinned);
if (sched_setaffinity(0, size, pinned)) {
SCX_ERR("Failed to pin task (%d)", errno);
goto out;
}
affinity_changed = true;
if (test_select_cpu_from_user(skel, "disjoint masks", second, true))
goto out;
} else {
fprintf(stderr, "Skipping disjoint masks: need two allowed CPUs\n");
}
/* Just sleeping is fine, plenty of scheduling events happening. */
sleep(1);
if (skel->data->uei.kind != EXIT_KIND(SCX_EXIT_NONE)) {
SCX_ERR("Scheduler exited unexpectedly");
goto out;
}
status = SCX_TEST_PASS;
out:
if (affinity_changed && sched_setaffinity(0, size, original)) {
SCX_ERR("Failed to restore affinity (%d)", errno);
status = SCX_TEST_FAIL;
}
bpf_link__destroy(link);
CPU_FREE(pinned);
CPU_FREE(original);
return status;
}
static void cleanup(void *ctx)
{
struct allowed_cpus *skel = ctx;
allowed_cpus__destroy(skel);
}
struct scx_test allowed_cpus = {
.name = "allowed_cpus",
.description = "Verify scx_bpf_select_cpu_and()",
.setup = setup,
.run = run,
.cleanup = cleanup,
};
REGISTER_SCX_TEST(&allowed_cpus)
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