On Wed, Jul 2, 2025 at 10:28 AM Leon Hwang <leon.hwang@xxxxxxxxx> wrote:
>
>
>
> On 2025/7/2 04:22, Andrii Nakryiko wrote:
> > On Tue, Jun 24, 2025 at 9:55 AM Leon Hwang <leon.hwang@xxxxxxxxx> wrote:
> >>
> >> This patch adds libbpf support for the BPF_F_CPU flag in percpu_array maps,
> >> introducing the following APIs:
> >>
> >> 1. bpf_map_update_elem_opts(): update with struct bpf_map_update_elem_opts
> >> 2. bpf_map_lookup_elem_opts(): lookup with struct bpf_map_lookup_elem_opts
> >> 3. bpf_map__update_elem_opts(): high-level wrapper with input validation
> >> 4. bpf_map__lookup_elem_opts(): high-level wrapper with input validation
> >>
> >> Behavior:
> >>
> >> * If opts->cpu == 0xFFFFFFFF, the update is applied to all CPUs.
> >> * Otherwise, it applies only to the specified CPU.
> >> * Lookup APIs retrieve values from the target CPU when BPF_F_CPU is used.
> >>
> >> Signed-off-by: Leon Hwang <leon.hwang@xxxxxxxxx>
> >> ---
> >> tools/lib/bpf/bpf.c | 37 +++++++++++++++++++++++
> >> tools/lib/bpf/bpf.h | 35 +++++++++++++++++++++-
> >> tools/lib/bpf/libbpf.c | 56 +++++++++++++++++++++++++++++++++++
> >> tools/lib/bpf/libbpf.h | 45 ++++++++++++++++++++++++++++
> >> tools/lib/bpf/libbpf.map | 4 +++
> >> tools/lib/bpf/libbpf_common.h | 12 ++++++++
> >> 6 files changed, 188 insertions(+), 1 deletion(-)
> >>
[...]
> >> };
> >> -#define bpf_map_batch_opts__last_field flags
> >> +#define bpf_map_batch_opts__last_field cpu
> >>
> >>
> >> /**
> >> @@ -286,6 +315,10 @@ 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 map, update value on all CPUs if **opts->cpu** is
> >> + * 0xFFFFFFFF, or on specified CPU otherwise.
> >> + *
> >> * @param fd BPF map file descriptor
> >> * @param keys pointer to an array of *count* keys
> >> * @param values pointer to an array of *count* values
> >> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> >> index 6445165a24f2..30400bdc20d9 100644
> >> --- a/tools/lib/bpf/libbpf.c
> >> +++ b/tools/lib/bpf/libbpf.c
> >> @@ -10636,6 +10636,34 @@ int bpf_map__lookup_elem(const struct bpf_map *map,
> >> return bpf_map_lookup_elem_flags(map->fd, key, value, flags);
> >> }
> >>
> >> +int bpf_map__lookup_elem_opts(const struct bpf_map *map, const void *key,
> >> + size_t key_sz, void *value, size_t value_sz,
> >> + const struct bpf_map_lookup_elem_opts *opts)
> >> +{
> >> + int nr_cpus = libbpf_num_possible_cpus();
> >> + __u32 cpu = OPTS_GET(opts, cpu, nr_cpus);
> >> + __u64 flags = OPTS_GET(opts, flags, 0);
> >> + int err;
> >> +
> >> + if (flags & BPF_F_CPU) {
> >> + if (map->def.type != BPF_MAP_TYPE_PERCPU_ARRAY)
> >> + return -EINVAL;
> >> + if (cpu >= nr_cpus)
> >> + return -E2BIG;
> >> + if (map->def.value_size != value_sz) {
> >> + pr_warn("map '%s': unexpected value size %zu provided, expected %u\n",
> >> + map->name, value_sz, map->def.value_size);
> >> + return -EINVAL;
> >> + }
> >
> > shouldn't this go into validate_map_op?..
> >
>
> It should.
>
> However, to avoid making validate_map_op really complicated, I'd like to
> add validate_map_cpu_op to wrap checking cpu and validate_map_op.
validate_map_op is meant to handle all the different conditions, let's
keep all that in one function
[...]
