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libbpf: Add BPF_F_CPU and BPF_F_ALL_CPUS flags support for percpu maps

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Add libbpf support for the BPF_F_CPU flag for percpu maps by embedding the
cpu info into the high 32 bits of:

1. **flags**: bpf_map_lookup_elem_flags(), bpf_map__lookup_elem(),
   bpf_map_update_elem() and bpf_map__update_elem()
2. **opts->elem_flags**: bpf_map_lookup_batch() and
   bpf_map_update_batch()

And the flag can be BPF_F_ALL_CPUS, but cannot be
'BPF_F_CPU | BPF_F_ALL_CPUS'.

Behavior:

* If the flag is BPF_F_ALL_CPUS, the update is applied across all CPUs.
* If the flag is BPF_F_CPU, it updates value only to the specified CPU.
* If the flag is BPF_F_CPU, lookup value only from the specified CPU.
* lookup does not support BPF_F_ALL_CPUS.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260107022022.12843-7-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Leon Hwang
2026-01-07 10:20:21 +08:00
committed by Andrii Nakryiko
parent a6d7ceaaeb
commit dc8673b28b
3 changed files with 36 additions and 19 deletions
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8
src/bpf.h
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@@ -289,6 +289,14 @@ LIBBPF_API int bpf_map_lookup_and_delete_batch(int fd, void *in_batch,
* Update spin_lock-ed map elements. This must be
* specified if the map value contains a spinlock.
*
* **BPF_F_CPU**
* As for percpu maps, update value on the specified CPU. And the cpu
* info is embedded into the high 32 bits of **opts->elem_flags**.
*
* **BPF_F_ALL_CPUS**
* As for percpu maps, update value across all CPUs. This flag cannot
* be used with BPF_F_CPU at the same time.
*
* @param fd BPF map file descriptor
* @param keys pointer to an array of *count* keys
* @param values pointer to an array of *count* values