From a6de18f310a511278c1ff16b96eb2d500eada725 Mon Sep 17 00:00:00 2001 From: David Vernet Date: Thu, 7 Dec 2023 15:08:42 -0600 Subject: [PATCH 1/2] bpf: Add bpf_cpumask_weight() kfunc It can be useful to query how many bits are set in a cpumask. For example, if you want to perform special logic for the last remaining core that's set in a mask. Let's therefore add a new bpf_cpumask_weight() kfunc which checks how many bits are set in a mask. Signed-off-by: David Vernet Acked-by: Yonghong Song Link: https://lore.kernel.org/r/20231207210843.168466-2-void@manifault.com Signed-off-by: Alexei Starovoitov --- Documentation/bpf/cpumasks.rst | 2 +- kernel/bpf/cpumask.c | 12 ++++++++++++ 2 files changed, 13 insertions(+), 1 deletion(-) diff --git a/Documentation/bpf/cpumasks.rst b/Documentation/bpf/cpumasks.rst index a22b6ad105fb..b5d47a04da5d 100644 --- a/Documentation/bpf/cpumasks.rst +++ b/Documentation/bpf/cpumasks.rst @@ -352,7 +352,7 @@ can be used to query the contents of cpumasks. .. kernel-doc:: kernel/bpf/cpumask.c :identifiers: bpf_cpumask_first bpf_cpumask_first_zero bpf_cpumask_first_and - bpf_cpumask_test_cpu + bpf_cpumask_test_cpu bpf_cpumask_weight .. kernel-doc:: kernel/bpf/cpumask.c :identifiers: bpf_cpumask_equal bpf_cpumask_intersects bpf_cpumask_subset diff --git a/kernel/bpf/cpumask.c b/kernel/bpf/cpumask.c index e01c741e54e7..7499b7d8c06f 100644 --- a/kernel/bpf/cpumask.c +++ b/kernel/bpf/cpumask.c @@ -405,6 +405,17 @@ __bpf_kfunc u32 bpf_cpumask_any_and_distribute(const struct cpumask *src1, return cpumask_any_and_distribute(src1, src2); } +/** + * bpf_cpumask_weight() - Return the number of bits in @cpumask. + * @cpumask: The cpumask being queried. + * + * Count the number of set bits in the given cpumask. + */ +__bpf_kfunc u32 bpf_cpumask_weight(const struct cpumask *cpumask) +{ + return cpumask_weight(cpumask); +} + __bpf_kfunc_end_defs(); BTF_SET8_START(cpumask_kfunc_btf_ids) @@ -432,6 +443,7 @@ BTF_ID_FLAGS(func, bpf_cpumask_full, KF_RCU) BTF_ID_FLAGS(func, bpf_cpumask_copy, KF_RCU) BTF_ID_FLAGS(func, bpf_cpumask_any_distribute, KF_RCU) BTF_ID_FLAGS(func, bpf_cpumask_any_and_distribute, KF_RCU) +BTF_ID_FLAGS(func, bpf_cpumask_weight, KF_RCU) BTF_SET8_END(cpumask_kfunc_btf_ids) static const struct btf_kfunc_id_set cpumask_kfunc_set = { From 88f6047191e69bdd02cf1b9b5b514f7e514e8b86 Mon Sep 17 00:00:00 2001 From: David Vernet Date: Thu, 7 Dec 2023 15:08:43 -0600 Subject: [PATCH 2/2] selftests/bpf: Add test for bpf_cpumask_weight() kfunc The new bpf_cpumask_weight() kfunc can be used to count the number of bits that are set in a struct cpumask* kptr. Let's add a selftest to verify its behavior. Signed-off-by: David Vernet Acked-by: Yonghong Song Link: https://lore.kernel.org/r/20231207210843.168466-3-void@manifault.com Signed-off-by: Alexei Starovoitov --- .../selftests/bpf/prog_tests/cpumask.c | 1 + .../selftests/bpf/progs/cpumask_common.h | 1 + .../selftests/bpf/progs/cpumask_success.c | 43 +++++++++++++++++++ 3 files changed, 45 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/cpumask.c b/tools/testing/selftests/bpf/prog_tests/cpumask.c index 756ea8b590b6..c2e886399e3c 100644 --- a/tools/testing/selftests/bpf/prog_tests/cpumask.c +++ b/tools/testing/selftests/bpf/prog_tests/cpumask.c @@ -18,6 +18,7 @@ static const char * const cpumask_success_testcases[] = { "test_insert_leave", "test_insert_remove_release", "test_global_mask_rcu", + "test_cpumask_weight", }; static void verify_success(const char *prog_name) diff --git a/tools/testing/selftests/bpf/progs/cpumask_common.h b/tools/testing/selftests/bpf/progs/cpumask_common.h index b15c588ace15..0cd4aebb97cf 100644 --- a/tools/testing/selftests/bpf/progs/cpumask_common.h +++ b/tools/testing/selftests/bpf/progs/cpumask_common.h @@ -54,6 +54,7 @@ bool bpf_cpumask_full(const struct cpumask *cpumask) __ksym; void bpf_cpumask_copy(struct bpf_cpumask *dst, const struct cpumask *src) __ksym; u32 bpf_cpumask_any_distribute(const struct cpumask *src) __ksym; u32 bpf_cpumask_any_and_distribute(const struct cpumask *src1, const struct cpumask *src2) __ksym; +u32 bpf_cpumask_weight(const struct cpumask *cpumask) __ksym; void bpf_rcu_read_lock(void) __ksym; void bpf_rcu_read_unlock(void) __ksym; diff --git a/tools/testing/selftests/bpf/progs/cpumask_success.c b/tools/testing/selftests/bpf/progs/cpumask_success.c index 674a63424dee..fc3666edf456 100644 --- a/tools/testing/selftests/bpf/progs/cpumask_success.c +++ b/tools/testing/selftests/bpf/progs/cpumask_success.c @@ -460,6 +460,49 @@ int BPF_PROG(test_global_mask_rcu, struct task_struct *task, u64 clone_flags) return 0; } +SEC("tp_btf/task_newtask") +int BPF_PROG(test_cpumask_weight, struct task_struct *task, u64 clone_flags) +{ + struct bpf_cpumask *local; + + if (!is_test_task()) + return 0; + + local = create_cpumask(); + if (!local) + return 0; + + if (bpf_cpumask_weight(cast(local)) != 0) { + err = 3; + goto out; + } + + bpf_cpumask_set_cpu(0, local); + if (bpf_cpumask_weight(cast(local)) != 1) { + err = 4; + goto out; + } + + /* + * Make sure that adding additional CPUs changes the weight. Test to + * see whether the CPU was set to account for running on UP machines. + */ + bpf_cpumask_set_cpu(1, local); + if (bpf_cpumask_test_cpu(1, cast(local)) && bpf_cpumask_weight(cast(local)) != 2) { + err = 5; + goto out; + } + + bpf_cpumask_clear(local); + if (bpf_cpumask_weight(cast(local)) != 0) { + err = 6; + goto out; + } +out: + bpf_cpumask_release(local); + return 0; +} + SEC("tp_btf/task_newtask") __success int BPF_PROG(test_refcount_null_tracking, struct task_struct *task, u64 clone_flags)