diff mbox series

[bpf-next,2/2] selftests/bpf: Add selftest for bits iter

Message ID 20240218114818.13585-3-laoar.shao@gmail.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series bpf: Add a generic bits iterator | expand

Checks

Context Check Description
bpf/vmtest-bpf-next-PR fail PR summary
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 8 this patch: 8
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Commit Message

Yafang Shao Feb. 18, 2024, 11:48 a.m. UTC 
Add selftests for the newly added bits iter.
- bits_iter_success
  - The number of CPUs should be expected when iterating over a cpumask
  - percpu data extracted from the percpu struct should be expected
  - RCU lock is not required
  - It is fine without calling bpf_iter_cpumask_next()
  - It can work as expected when invalid arguments are passed

- bits_iter_failure
  - bpf_iter_bits_destroy() is required after calling
    bpf_iter_bits_new()
  - bpf_iter_bits_destroy() can only destroy an initialized iter
  - bpf_iter_bits_next() must use an initialized iter

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 tools/testing/selftests/bpf/config            |   1 +
 .../selftests/bpf/prog_tests/bits_iter.c      | 180 ++++++++++++++++++
 .../bpf/progs/test_bits_iter_failure.c        |  53 ++++++
 .../bpf/progs/test_bits_iter_success.c        | 146 ++++++++++++++
 4 files changed, 380 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/bits_iter.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_bits_iter_failure.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_bits_iter_success.c

Comments

Alexei Starovoitov Feb. 22, 2024, 5:36 p.m. UTC | #1 
On Sun, Feb 18, 2024 at 3:49 AM Yafang Shao <laoar.shao@gmail.com> wrote:
>
> Add selftests for the newly added bits iter.
> - bits_iter_success
>   - The number of CPUs should be expected when iterating over a cpumask
>   - percpu data extracted from the percpu struct should be expected
>   - RCU lock is not required
>   - It is fine without calling bpf_iter_cpumask_next()
>   - It can work as expected when invalid arguments are passed
>
> - bits_iter_failure
>   - bpf_iter_bits_destroy() is required after calling
>     bpf_iter_bits_new()
>   - bpf_iter_bits_destroy() can only destroy an initialized iter
>   - bpf_iter_bits_next() must use an initialized iter
>
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> ---
>  tools/testing/selftests/bpf/config            |   1 +
>  .../selftests/bpf/prog_tests/bits_iter.c      | 180 ++++++++++++++++++
>  .../bpf/progs/test_bits_iter_failure.c        |  53 ++++++
>  .../bpf/progs/test_bits_iter_success.c        | 146 ++++++++++++++
>  4 files changed, 380 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/bits_iter.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_bits_iter_failure.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_bits_iter_success.c
>
> diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config
> index 01f241ea2c67..dd4b0935e35f 100644
> --- a/tools/testing/selftests/bpf/config
> +++ b/tools/testing/selftests/bpf/config
> @@ -78,6 +78,7 @@ CONFIG_NF_CONNTRACK_MARK=y
>  CONFIG_NF_DEFRAG_IPV4=y
>  CONFIG_NF_DEFRAG_IPV6=y
>  CONFIG_NF_NAT=y
> +CONFIG_PSI=y
>  CONFIG_RC_CORE=y
>  CONFIG_SECURITY=y
>  CONFIG_SECURITYFS=y
> diff --git a/tools/testing/selftests/bpf/prog_tests/bits_iter.c b/tools/testing/selftests/bpf/prog_tests/bits_iter.c
> new file mode 100644
> index 000000000000..778a7c942dba
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/bits_iter.c
> @@ -0,0 +1,180 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2024 Yafang Shao <laoar.shao@gmail.com> */
> +
> +#define _GNU_SOURCE
> +#include <sched.h>
> +
> +#include <test_progs.h>
> +#include "test_bits_iter_success.skel.h"
> +#include "test_bits_iter_failure.skel.h"
> +#include "cgroup_helpers.h"
> +
> +static const char * const positive_testcases[] = {
> +       "cpumask_iter",
> +};
> +
> +static const char * const negative_testcases[] = {
> +       "null_pointer",
> +       "zero_bit",
> +       "no_mem",
> +       "invalid_bits"
> +};
> +
> +static int read_percpu_data(struct bpf_link *link, int nr_cpu_exp, int nr_running_exp)
> +{
> +       int iter_fd, len, item, nr_running, psi_running, nr_cpus, err = -1;
> +       char buf[128];
> +       size_t left;
> +       char *p;
> +
> +       iter_fd = bpf_iter_create(bpf_link__fd(link));
> +       if (!ASSERT_GE(iter_fd, 0, "iter_fd"))
> +               return -1;
> +
> +       memset(buf, 0, sizeof(buf));
> +       left = ARRAY_SIZE(buf);
> +       p = buf;
> +       while ((len = read(iter_fd, p, left)) > 0) {
> +               p += len;
> +               left -= len;
> +       }
> +
> +       item = sscanf(buf, "nr_running %u nr_cpus %u psi_running %u\n",
> +                     &nr_running, &nr_cpus, &psi_running);
> +       if (!ASSERT_EQ(item, 3, "seq_format"))
> +               goto out;
> +       if (!ASSERT_EQ(nr_cpus, nr_cpu_exp, "nr_cpus"))
> +               goto out;
> +       if (!ASSERT_GE(nr_running, nr_running_exp, "nr_running"))
> +               goto out;
> +       if (!ASSERT_GE(psi_running, nr_running_exp, "psi_running"))
> +               goto out;
> +
> +       err = 0;
> +out:
> +       close(iter_fd);
> +       return err;
> +}

..
> +
> +       /* Case 1): Enable all possible CPUs */
> +       CPU_ZERO(&set);
> +       for (i = 0; i < nr_cpus; i++)
> +               CPU_SET(i, &set);
> +       err = sched_setaffinity(skel->bss->pid, sizeof(set), &set);
> +       if (!ASSERT_OK(err, "setaffinity_all_cpus"))
> +               goto free_link;
> +       err = read_percpu_data(link, nr_cpus, 1);
> +       if (!ASSERT_OK(err, "read_percpu_data"))
> +               goto free_link;

The patch 1 looks good, but this test fails on s390.

read_percpu_data:FAIL:nr_cpus unexpected nr_cpus: actual 0 != expected 2
verify_iter_success:FAIL:read_percpu_data unexpected error: -1 (errno 95)

Please see CI.

So either add it to DENYLIST.s390x in the same commit or make it work.

pw-bot: cr
Yafang Shao Feb. 23, 2024, 2:29 a.m. UTC | #2 
On Fri, Feb 23, 2024 at 1:36 AM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Sun, Feb 18, 2024 at 3:49 AM Yafang Shao <laoar.shao@gmail.com> wrote:
> >
> > Add selftests for the newly added bits iter.
> > - bits_iter_success
> >   - The number of CPUs should be expected when iterating over a cpumask
> >   - percpu data extracted from the percpu struct should be expected
> >   - RCU lock is not required
> >   - It is fine without calling bpf_iter_cpumask_next()
> >   - It can work as expected when invalid arguments are passed
> >
> > - bits_iter_failure
> >   - bpf_iter_bits_destroy() is required after calling
> >     bpf_iter_bits_new()
> >   - bpf_iter_bits_destroy() can only destroy an initialized iter
> >   - bpf_iter_bits_next() must use an initialized iter
> >
> > Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> > ---
> >  tools/testing/selftests/bpf/config            |   1 +
> >  .../selftests/bpf/prog_tests/bits_iter.c      | 180 ++++++++++++++++++
> >  .../bpf/progs/test_bits_iter_failure.c        |  53 ++++++
> >  .../bpf/progs/test_bits_iter_success.c        | 146 ++++++++++++++
> >  4 files changed, 380 insertions(+)
> >  create mode 100644 tools/testing/selftests/bpf/prog_tests/bits_iter.c
> >  create mode 100644 tools/testing/selftests/bpf/progs/test_bits_iter_failure.c
> >  create mode 100644 tools/testing/selftests/bpf/progs/test_bits_iter_success.c
> >
> > diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config
> > index 01f241ea2c67..dd4b0935e35f 100644
> > --- a/tools/testing/selftests/bpf/config
> > +++ b/tools/testing/selftests/bpf/config
> > @@ -78,6 +78,7 @@ CONFIG_NF_CONNTRACK_MARK=y
> >  CONFIG_NF_DEFRAG_IPV4=y
> >  CONFIG_NF_DEFRAG_IPV6=y
> >  CONFIG_NF_NAT=y
> > +CONFIG_PSI=y
> >  CONFIG_RC_CORE=y
> >  CONFIG_SECURITY=y
> >  CONFIG_SECURITYFS=y
> > diff --git a/tools/testing/selftests/bpf/prog_tests/bits_iter.c b/tools/testing/selftests/bpf/prog_tests/bits_iter.c
> > new file mode 100644
> > index 000000000000..778a7c942dba
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/bits_iter.c
> > @@ -0,0 +1,180 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/* Copyright (c) 2024 Yafang Shao <laoar.shao@gmail.com> */
> > +
> > +#define _GNU_SOURCE
> > +#include <sched.h>
> > +
> > +#include <test_progs.h>
> > +#include "test_bits_iter_success.skel.h"
> > +#include "test_bits_iter_failure.skel.h"
> > +#include "cgroup_helpers.h"
> > +
> > +static const char * const positive_testcases[] = {
> > +       "cpumask_iter",
> > +};
> > +
> > +static const char * const negative_testcases[] = {
> > +       "null_pointer",
> > +       "zero_bit",
> > +       "no_mem",
> > +       "invalid_bits"
> > +};
> > +
> > +static int read_percpu_data(struct bpf_link *link, int nr_cpu_exp, int nr_running_exp)
> > +{
> > +       int iter_fd, len, item, nr_running, psi_running, nr_cpus, err = -1;
> > +       char buf[128];
> > +       size_t left;
> > +       char *p;
> > +
> > +       iter_fd = bpf_iter_create(bpf_link__fd(link));
> > +       if (!ASSERT_GE(iter_fd, 0, "iter_fd"))
> > +               return -1;
> > +
> > +       memset(buf, 0, sizeof(buf));
> > +       left = ARRAY_SIZE(buf);
> > +       p = buf;
> > +       while ((len = read(iter_fd, p, left)) > 0) {
> > +               p += len;
> > +               left -= len;
> > +       }
> > +
> > +       item = sscanf(buf, "nr_running %u nr_cpus %u psi_running %u\n",
> > +                     &nr_running, &nr_cpus, &psi_running);
> > +       if (!ASSERT_EQ(item, 3, "seq_format"))
> > +               goto out;
> > +       if (!ASSERT_EQ(nr_cpus, nr_cpu_exp, "nr_cpus"))
> > +               goto out;
> > +       if (!ASSERT_GE(nr_running, nr_running_exp, "nr_running"))
> > +               goto out;
> > +       if (!ASSERT_GE(psi_running, nr_running_exp, "psi_running"))
> > +               goto out;
> > +
> > +       err = 0;
> > +out:
> > +       close(iter_fd);
> > +       return err;
> > +}
>
> ..
> > +
> > +       /* Case 1): Enable all possible CPUs */
> > +       CPU_ZERO(&set);
> > +       for (i = 0; i < nr_cpus; i++)
> > +               CPU_SET(i, &set);
> > +       err = sched_setaffinity(skel->bss->pid, sizeof(set), &set);
> > +       if (!ASSERT_OK(err, "setaffinity_all_cpus"))
> > +               goto free_link;
> > +       err = read_percpu_data(link, nr_cpus, 1);
> > +       if (!ASSERT_OK(err, "read_percpu_data"))
> > +               goto free_link;
>
> The patch 1 looks good, but this test fails on s390.
>
> read_percpu_data:FAIL:nr_cpus unexpected nr_cpus: actual 0 != expected 2
> verify_iter_success:FAIL:read_percpu_data unexpected error: -1 (errno 95)
>
> Please see CI.
>
> So either add it to DENYLIST.s390x in the same commit or make it work.
>
> pw-bot: cr

The reason for the failure on s390x architecture is currently unclear.
One plausible explanation is that total_nr_cpus remains 0 when
executing the following code:

    bpf_for_each(bits, cpu, p->cpus_ptr, total_nr_cpus)

This is despite setting total_nr_cpus to the value obtained from
libbpf_num_possible_cpus():

    skel->bss->total_nr_cpus = libbpf_num_possible_cpus();

A potential workaround could involve using a hardcoded number of CPUs,
such as 8192, instead of relying on total_nr_cpus. This approach might
mitigate the issue temporarily.
Eduard Zingerman Feb. 23, 2024, 11:52 a.m. UTC | #3 
On Fri, 2024-02-23 at 10:29 +0800, Yafang Shao wrote:

[...]

> > The patch 1 looks good, but this test fails on s390.
> > 
> > read_percpu_data:FAIL:nr_cpus unexpected nr_cpus: actual 0 != expected 2
> > verify_iter_success:FAIL:read_percpu_data unexpected error: -1 (errno 95)
> > 
> > Please see CI.
> > 
> > So either add it to DENYLIST.s390x in the same commit or make it work.
> > 
> > pw-bot: cr
> 
> The reason for the failure on s390x architecture is currently unclear.
> One plausible explanation is that total_nr_cpus remains 0 when
> executing the following code:
> 
>     bpf_for_each(bits, cpu, p->cpus_ptr, total_nr_cpus)
> 
> This is despite setting total_nr_cpus to the value obtained from
> libbpf_num_possible_cpus():
> 
>     skel->bss->total_nr_cpus = libbpf_num_possible_cpus();
> 
> A potential workaround could involve using a hardcoded number of CPUs,
> such as 8192, instead of relying on total_nr_cpus. This approach might
> mitigate the issue temporarily. 

I'm sorry, but is it really necessary to deal with total number of
CPUs in a test for bit iterator?
Tbh, cpumask_iter / verify_iter_success seem to be over-complicated.
Would it be possible to reuse test_loader.c's RUN_TESTS for this feature?
It supports __retval(...) annotation, so it should be possible to:
- create a map (even a constant map) with some known data;
- peek a BPF program type that supports BPF_PROG_TEST_RUN syscall command;
- organize test BPF programs so that they create bit iterators for
  this test data and return some expected quantities (e.g. a sum),
  verified by __retval.

This should limit the amount of code on prog_tests/*.c side
to the bare minimum.
Yafang Shao Feb. 25, 2024, 2:29 a.m. UTC | #4 
On Fri, Feb 23, 2024 at 7:52 PM Eduard Zingerman <eddyz87@gmail.com> wrote:
>
> On Fri, 2024-02-23 at 10:29 +0800, Yafang Shao wrote:
>
> [...]
>
> > > The patch 1 looks good, but this test fails on s390.
> > >
> > > read_percpu_data:FAIL:nr_cpus unexpected nr_cpus: actual 0 != expected 2
> > > verify_iter_success:FAIL:read_percpu_data unexpected error: -1 (errno 95)
> > >
> > > Please see CI.
> > >
> > > So either add it to DENYLIST.s390x in the same commit or make it work.
> > >
> > > pw-bot: cr
> >
> > The reason for the failure on s390x architecture is currently unclear.
> > One plausible explanation is that total_nr_cpus remains 0 when
> > executing the following code:
> >
> >     bpf_for_each(bits, cpu, p->cpus_ptr, total_nr_cpus)
> >
> > This is despite setting total_nr_cpus to the value obtained from
> > libbpf_num_possible_cpus():
> >
> >     skel->bss->total_nr_cpus = libbpf_num_possible_cpus();
> >
> > A potential workaround could involve using a hardcoded number of CPUs,
> > such as 8192, instead of relying on total_nr_cpus. This approach might
> > mitigate the issue temporarily.
>
> I'm sorry, but is it really necessary to deal with total number of
> CPUs in a test for bit iterator?

The CPU number verification is served to validate the functionality of
bpf_iter_bits_next(). However, I believe we can streamline the logic
by removing the surrounding code.

> Tbh, cpumask_iter / verify_iter_success seem to be over-complicated.
> Would it be possible to reuse test_loader.c's RUN_TESTS for this feature?
> It supports __retval(...) annotation, so it should be possible to:
> - create a map (even a constant map) with some known data;
> - peek a BPF program type that supports BPF_PROG_TEST_RUN syscall command;
> - organize test BPF programs so that they create bit iterators for
>   this test data and return some expected quantities (e.g. a sum),
>   verified by __retval.
>
> This should limit the amount of code on prog_tests/*.c side
> to the bare minimum.

Thank you for your suggestion. I will consider it carefully.
kernel test robot Feb. 25, 2024, 7:38 p.m. UTC | #5 
Hi Yafang,

kernel test robot noticed the following build errors:

[auto build test ERROR on bpf-next/master]

url:    https://github.com/intel-lab-lkp/linux/commits/Yafang-Shao/bpf-Add-bits-iterator/20240218-195123
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
patch link:    https://lore.kernel.org/r/20240218114818.13585-3-laoar.shao%40gmail.com
patch subject: [PATCH bpf-next 2/2] selftests/bpf: Add selftest for bits iter
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240226/202402260354.rwSw5NBc-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202402260354.rwSw5NBc-lkp@intel.com/

All errors (new ones prefixed by >>):

>> progs/test_bits_iter_success.c:55:27: error: incomplete definition of type 'struct psi_group_cpu'
      55 |                 psi_nr_running += groupc->tasks[NR_RUNNING];
         |                                   ~~~~~~^
   progs/test_bits_iter_success.c:13:21: note: forward declaration of 'struct psi_group_cpu'
      13 | extern const struct psi_group_cpu system_group_pcpu __ksym __weak;
         |                     ^
>> progs/test_bits_iter_success.c:55:35: error: use of undeclared identifier 'NR_RUNNING'; did you mean 'T_RUNNING'?
      55 |                 psi_nr_running += groupc->tasks[NR_RUNNING];
         |                                                 ^~~~~~~~~~
         |                                                 T_RUNNING
   /tools/include/vmlinux.h:48349:3: note: 'T_RUNNING' declared here
    48349 |                 T_RUNNING = 0,
          |                 ^
   2 errors generated.
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config
index 01f241ea2c67..dd4b0935e35f 100644
--- a/tools/testing/selftests/bpf/config
+++ b/tools/testing/selftests/bpf/config
@@ -78,6 +78,7 @@  CONFIG_NF_CONNTRACK_MARK=y
 CONFIG_NF_DEFRAG_IPV4=y
 CONFIG_NF_DEFRAG_IPV6=y
 CONFIG_NF_NAT=y
+CONFIG_PSI=y
 CONFIG_RC_CORE=y
 CONFIG_SECURITY=y
 CONFIG_SECURITYFS=y
diff --git a/tools/testing/selftests/bpf/prog_tests/bits_iter.c b/tools/testing/selftests/bpf/prog_tests/bits_iter.c
new file mode 100644
index 000000000000..778a7c942dba
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/bits_iter.c
@@ -0,0 +1,180 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Yafang Shao <laoar.shao@gmail.com> */
+
+#define _GNU_SOURCE
+#include <sched.h>
+
+#include <test_progs.h>
+#include "test_bits_iter_success.skel.h"
+#include "test_bits_iter_failure.skel.h"
+#include "cgroup_helpers.h"
+
+static const char * const positive_testcases[] = {
+	"cpumask_iter",
+};
+
+static const char * const negative_testcases[] = {
+	"null_pointer",
+	"zero_bit",
+	"no_mem",
+	"invalid_bits"
+};
+
+static int read_percpu_data(struct bpf_link *link, int nr_cpu_exp, int nr_running_exp)
+{
+	int iter_fd, len, item, nr_running, psi_running, nr_cpus, err = -1;
+	char buf[128];
+	size_t left;
+	char *p;
+
+	iter_fd = bpf_iter_create(bpf_link__fd(link));
+	if (!ASSERT_GE(iter_fd, 0, "iter_fd"))
+		return -1;
+
+	memset(buf, 0, sizeof(buf));
+	left = ARRAY_SIZE(buf);
+	p = buf;
+	while ((len = read(iter_fd, p, left)) > 0) {
+		p += len;
+		left -= len;
+	}
+
+	item = sscanf(buf, "nr_running %u nr_cpus %u psi_running %u\n",
+		      &nr_running, &nr_cpus, &psi_running);
+	if (!ASSERT_EQ(item, 3, "seq_format"))
+		goto out;
+	if (!ASSERT_EQ(nr_cpus, nr_cpu_exp, "nr_cpus"))
+		goto out;
+	if (!ASSERT_GE(nr_running, nr_running_exp, "nr_running"))
+		goto out;
+	if (!ASSERT_GE(psi_running, nr_running_exp, "psi_running"))
+		goto out;
+
+	err = 0;
+out:
+	close(iter_fd);
+	return err;
+}
+
+static void verify_iter_success(const char *prog_name, bool negtive)
+{
+	DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
+	int cgrp_fd, nr_cpus, err, i, chosen = 0;
+	struct test_bits_iter_success *skel;
+	union bpf_iter_link_info linfo;
+	struct bpf_program *prog;
+	struct bpf_link *link;
+	cpu_set_t set;
+
+	if (setup_cgroup_environment())
+		return;
+
+	/* Utilize the cgroup iter */
+	cgrp_fd = get_root_cgroup();
+	if (!ASSERT_GE(cgrp_fd, 0, "create_cgrp"))
+		goto cleanup;
+
+	skel = test_bits_iter_success__open();
+	if (!ASSERT_OK_PTR(skel, "cpumask_iter_success__open"))
+		goto close_fd;
+
+	skel->bss->pid = getpid();
+	nr_cpus = libbpf_num_possible_cpus();
+	skel->bss->total_nr_cpus = nr_cpus;
+
+	err = test_bits_iter_success__load(skel);
+	if (!ASSERT_OK(err, "cpumask_iter_success__load"))
+		goto destroy;
+
+	prog = bpf_object__find_program_by_name(skel->obj, prog_name);
+	if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name"))
+		goto destroy;
+
+	memset(&linfo, 0, sizeof(linfo));
+	linfo.cgroup.cgroup_fd = cgrp_fd;
+	linfo.cgroup.order = BPF_CGROUP_ITER_SELF_ONLY;
+	opts.link_info = &linfo;
+	opts.link_info_len = sizeof(linfo);
+	link = bpf_program__attach_iter(prog, &opts);
+	if (!ASSERT_OK_PTR(link, "bpf_program__attach"))
+		goto destroy;
+
+	if (negtive)
+		goto negtive;
+
+	/* Case 1): Enable all possible CPUs */
+	CPU_ZERO(&set);
+	for (i = 0; i < nr_cpus; i++)
+		CPU_SET(i, &set);
+	err = sched_setaffinity(skel->bss->pid, sizeof(set), &set);
+	if (!ASSERT_OK(err, "setaffinity_all_cpus"))
+		goto free_link;
+	err = read_percpu_data(link, nr_cpus, 1);
+	if (!ASSERT_OK(err, "read_percpu_data"))
+		goto free_link;
+	if (!ASSERT_OK(skel->bss->err, "null_rq"))
+		goto free_link;
+
+	/* Case 2): CPU0 only */
+	CPU_ZERO(&set);
+	CPU_SET(0, &set);
+	err = sched_setaffinity(skel->bss->pid, sizeof(set), &set);
+	if (!ASSERT_OK(err, "setaffinity_cpu0"))
+		goto free_link;
+	err = read_percpu_data(link, 1, 1);
+	if (!ASSERT_OK(err, "read_percpu_data"))
+		goto free_link;
+	if (!ASSERT_OK(skel->bss->err, "null_rq_psi"))
+		goto free_link;
+
+	/* Case 3): Partial CPUs */
+	CPU_ZERO(&set);
+	for (i = 0; i < nr_cpus; i++) {
+		if (i < 4 && i & 0x1)
+			continue;
+		if (i > 8 && i & 0x2)
+			continue;
+		CPU_SET(i, &set);
+		chosen++;
+	}
+	err = sched_setaffinity(skel->bss->pid, sizeof(set), &set);
+	if (!ASSERT_OK(err, "setaffinity_partial_cpus"))
+		goto free_link;
+	err = read_percpu_data(link, chosen, 1);
+	if (!ASSERT_OK(err, "read_percpu_data"))
+		goto free_link;
+
+negtive:
+	ASSERT_OK(skel->bss->err, "null_rq_psi");
+
+free_link:
+	bpf_link__destroy(link);
+destroy:
+	test_bits_iter_success__destroy(skel);
+close_fd:
+	close(cgrp_fd);
+cleanup:
+	cleanup_cgroup_environment();
+}
+
+void test_bits_iter(void)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(positive_testcases); i++) {
+		if (!test__start_subtest(positive_testcases[i]))
+			continue;
+
+		verify_iter_success(positive_testcases[i], false);
+	}
+
+	for (i = 0; i < ARRAY_SIZE(negative_testcases); i++) {
+		if (!test__start_subtest(negative_testcases[i]))
+			continue;
+
+		verify_iter_success(negative_testcases[i], true);
+	}
+
+	RUN_TESTS(test_bits_iter_success);
+	RUN_TESTS(test_bits_iter_failure);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_bits_iter_failure.c b/tools/testing/selftests/bpf/progs/test_bits_iter_failure.c
new file mode 100644
index 000000000000..c51f18f4f334
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_bits_iter_failure.c
@@ -0,0 +1,53 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2024 Yafang Shao <laoar.shao@gmail.com> */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#include "bpf_misc.h"
+#include "task_kfunc_common.h"
+
+char _license[] SEC("license") = "GPL";
+
+int bpf_iter_bits_new(struct bpf_iter_bits *it, const void *unsafe_ptr, u32 nr_bits) __ksym __weak;
+int *bpf_iter_bits_next(struct bpf_iter_bits *it) __ksym __weak;
+void bpf_iter_bits_destroy(struct bpf_iter_bits *it) __ksym __weak;
+
+SEC("iter.s/cgroup")
+__failure __msg("Unreleased reference id=3 alloc_insn=10")
+int BPF_PROG(no_destroy, struct bpf_iter_meta *meta, struct cgroup *cgrp)
+{
+	struct bpf_iter_bits it;
+	struct task_struct *p;
+
+	p = bpf_task_from_pid(1);
+	if (!p)
+		return 1;
+
+	bpf_iter_bits_new(&it, p->cpus_ptr, 8192);
+
+	bpf_iter_bits_next(&it);
+	bpf_task_release(p);
+	return 0;
+}
+
+SEC("iter/cgroup")
+__failure __msg("expected an initialized iter_bits as arg #1")
+int BPF_PROG(next_uninit, struct bpf_iter_meta *meta, struct cgroup *cgrp)
+{
+	struct bpf_iter_bits *it = NULL;
+
+	bpf_iter_bits_next(it);
+	return 0;
+}
+
+SEC("iter/cgroup")
+__failure __msg("expected an initialized iter_bits as arg #1")
+int BPF_PROG(destroy_uninit, struct bpf_iter_meta *meta, struct cgroup *cgrp)
+{
+	struct bpf_iter_bits it = {};
+
+	bpf_iter_bits_destroy(&it);
+	return 0;
+}
diff --git a/tools/testing/selftests/bpf/progs/test_bits_iter_success.c b/tools/testing/selftests/bpf/progs/test_bits_iter_success.c
new file mode 100644
index 000000000000..6e5f12ad17ce
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_bits_iter_success.c
@@ -0,0 +1,146 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2024 Yafang Shao <laoar.shao@gmail.com> */
+
+#include "vmlinux.h"
+#include <linux/const.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#include "task_kfunc_common.h"
+
+char _license[] SEC("license") = "GPL";
+
+extern const struct psi_group_cpu system_group_pcpu __ksym __weak;
+extern const struct rq runqueues __ksym __weak;
+
+int bpf_iter_bits_new(struct bpf_iter_bits *it, const void *unsafe_ptr, u32 nr_bits) __ksym __weak;
+int *bpf_iter_bits_next(struct bpf_iter_bits *it) __ksym __weak;
+void bpf_iter_bits_destroy(struct bpf_iter_bits *it) __ksym __weak;
+
+int pid, err, total_nr_cpus;
+
+SEC("iter.s/cgroup")
+int BPF_PROG(cpumask_iter, struct bpf_iter_meta *meta, struct cgroup *cgrp)
+{
+	u32 nr_running = 0, psi_nr_running = 0, nr_cpus = 0;
+	struct psi_group_cpu *groupc;
+	struct task_struct *p;
+	struct rq *rq;
+	int *cpu;
+
+	/* epilogue */
+	if (!cgrp)
+		return 0;
+
+	p = bpf_task_from_pid(pid);
+	if (!p)
+		return 1;
+
+	bpf_for_each(bits, cpu, p->cpus_ptr, total_nr_cpus) {
+		rq = (struct rq *)bpf_per_cpu_ptr(&runqueues, *cpu);
+		/* Each valid CPU must have a runqueue, even if it is offline. */
+		if (!rq) {
+			err++;
+			continue;
+		}
+
+		nr_running += rq->nr_running;
+		nr_cpus++;
+
+		groupc = (struct psi_group_cpu *)bpf_per_cpu_ptr(&system_group_pcpu, *cpu);
+		if (!groupc) {
+			err++;
+			continue;
+		}
+		psi_nr_running += groupc->tasks[NR_RUNNING];
+	}
+	BPF_SEQ_PRINTF(meta->seq, "nr_running %u nr_cpus %u psi_running %u\n",
+		       nr_running, nr_cpus, psi_nr_running);
+	bpf_task_release(p);
+	return 0;
+}
+
+SEC("iter.s/cgroup")
+int BPF_PROG(null_pointer, struct bpf_iter_meta *meta, struct cgroup *cgrp)
+{
+	int *cpu;
+
+	bpf_for_each(bits, cpu, NULL, total_nr_cpus)
+		err++;
+	return 0;
+}
+
+SEC("iter.s/cgroup")
+int BPF_PROG(zero_bit, struct bpf_iter_meta *meta, struct cgroup *cgrp)
+{
+	struct task_struct *p;
+	int *cpu;
+
+	p = bpf_task_from_pid(pid);
+	if (!p)
+		return 1;
+
+	bpf_for_each(bits, cpu, p->cpus_ptr, 0)
+		err++;
+	bpf_task_release(p);
+	return 0;
+}
+
+SEC("iter.s/cgroup")
+int BPF_PROG(no_mem, struct bpf_iter_meta *meta, struct cgroup *cgrp)
+{
+	struct task_struct *p;
+	int *cpu;
+
+	p = bpf_task_from_pid(pid);
+	if (!p)
+		return 1;
+
+	/* The max size of memalloc is 4096, so it will fail to allocate (8192 * 8) */
+	bpf_for_each(bits, cpu, p->cpus_ptr, 8192 * 8)
+		err++;
+	bpf_task_release(p);
+	return 0;
+}
+
+SEC("iter/cgroup")
+int BPF_PROG(invalid_bits, struct bpf_iter_meta *meta, struct cgroup *cgrp)
+{
+	struct task_struct *p;
+	struct rq *rq;
+	int *cpu;
+
+	p = bpf_task_from_pid(pid);
+	if (!p)
+		return 1;
+
+	bpf_for_each(bits, cpu, p->cpus_ptr, 8192) {
+		rq = (struct rq *)bpf_per_cpu_ptr(&runqueues, *cpu);
+		/* For invalid CPU IDs, the rq must be NULL. */
+		if (!rq)
+			err++;
+	}
+	if (err)
+		err -= 8192 - total_nr_cpus;
+	bpf_task_release(p);
+	return 0;
+}
+
+SEC("iter.s/cgroup")
+int BPF_PROG(no_next, struct bpf_iter_meta *meta, struct cgroup *cgrp)
+{
+	struct bpf_iter_bits it;
+	struct task_struct *p;
+
+	p = bpf_task_from_pid(1);
+	if (!p)
+		return 1;
+
+	bpf_iter_bits_new(&it, p->cpus_ptr, 8192);
+
+	/* It is fine without calling bpf_iter_bits_next(). */
+
+	bpf_iter_bits_destroy(&it);
+	bpf_task_release(p);
+	return 0;
+}