linux-kernel - [PATCH bpf-next 1/5] bpf: Add bpf_cpumask_first

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Message-Id: <20230610035053.117605-1-void@manifault.com>
Date:   Fri,  9 Jun 2023 22:50:49 -0500
From:   David Vernet <void@...ifault.com>
To:     bpf@...r.kernel.org
Cc:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        martin.lau@...ux.dev, song@...nel.org, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
        haoluo@...gle.com, jolsa@...nel.org, linux-kernel@...r.kernel.org,
        kernel-team@...a.com, tj@...nel.org
Subject: [PATCH bpf-next 1/5] bpf: Add bpf_cpumask_first_and() kfunc

We currently provide bpf_cpumask_first(), bpf_cpumask_any(), and
bpf_cpumask_any_and() kfuncs. bpf_cpumask_any() and
bpf_cpumask_any_and() are confusing misnomers in that they actually just
call cpumask_first() and cpumask_first_and() respectively.

We'll replace them with bpf_cpumask_any_distribute() and
bpf_cpumask_any_distribute_and() kfuncs in a subsequent patch, so let's
ensure feature parity by adding a bpf_cpumask_first_and() kfunc to
account for bpf_cpumask_any_and() being removed.

Signed-off-by: David Vernet <void@...ifault.com>
---
 kernel/bpf/cpumask.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/kernel/bpf/cpumask.c b/kernel/bpf/cpumask.c
index 7efdf5d770ca..9416c8ac8a04 100644
--- a/kernel/bpf/cpumask.c
+++ b/kernel/bpf/cpumask.c
@@ -131,6 +131,21 @@ __bpf_kfunc u32 bpf_cpumask_first_zero(const struct cpumask *cpumask)
 	return cpumask_first_zero(cpumask);
 }
 
+/**
+ * bpf_cpumask_first_and() - Return the index of the first nonzero bit from the
+ *			     AND of two cpumasks.
+ * @src1: The first cpumask.
+ * @src2: The second cpumask.
+ *
+ * Find the index of the first nonzero bit of the AND of two cpumasks.
+ * struct bpf_cpumask pointers may be safely passed to @src1 and @src2.
+ */
+__bpf_kfunc u32 bpf_cpumask_first_and(const struct cpumask *src1,
+				      const struct cpumask *src2)
+{
+	return cpumask_first_and(src1, src2);
+}
+
 /**
  * bpf_cpumask_set_cpu() - Set a bit for a CPU in a BPF cpumask.
  * @cpu: The CPU to be set in the cpumask.
@@ -406,6 +421,7 @@ BTF_ID_FLAGS(func, bpf_cpumask_release, KF_RELEASE)
 BTF_ID_FLAGS(func, bpf_cpumask_acquire, KF_ACQUIRE | KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_cpumask_first, KF_RCU)
 BTF_ID_FLAGS(func, bpf_cpumask_first_zero, KF_RCU)
+BTF_ID_FLAGS(func, bpf_cpumask_first_and, KF_RCU)
 BTF_ID_FLAGS(func, bpf_cpumask_set_cpu, KF_RCU)
 BTF_ID_FLAGS(func, bpf_cpumask_clear_cpu, KF_RCU)
 BTF_ID_FLAGS(func, bpf_cpumask_test_cpu, KF_RCU)
-- 
2.40.1