On 2025/7/18 23:57, Andrii Nakryiko wrote: > On Thu, Jul 17, 2025 at 12:38 PM 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 == (u32)~0, 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> >> --- > > please use "libbpf: " prefix, not "bpf,libbpf:" > Ack. > > Then see my comment on flags vs separate field for cpu passing. If we > go with just using flags, then I'd probably drop all the new libbpf > APIs, because we already have bpf_map_lookup_elem_flags() and > bpf_map_update_elem() (the latter accepts flags), so as far as > low-level API we are good. > All the new libbpf APIs are unnecessary when pass the cpu through flags. > The comment describing the new BPF_F_CPU flag is good, so let's add > it, but place it into bpf_map__lookup_elem() description (which, btw, > also accepts flags, so no changes to API itself is necessary). Same > for bpf_map__update_elem(). > No problem. > validate_map_op() logic will stay, but just will extract cpu from flags, right? > Yes, it is. > So overall less API churn, but same possibilities for users (plus we > get better documentation, which is always nice). > When users want to use this feature, they should follow the libbpf API's documentation, no matter whether the cpu is separated or flags-embedded. Thanks, Leon >> tools/lib/bpf/bpf.c | 23 ++++++++++++++ >> tools/lib/bpf/bpf.h | 36 +++++++++++++++++++++- >> tools/lib/bpf/libbpf.c | 56 +++++++++++++++++++++++++++++++---- >> tools/lib/bpf/libbpf.h | 53 ++++++++++++++++++++++++++++----- >> tools/lib/bpf/libbpf.map | 5 ++++ >> tools/lib/bpf/libbpf_common.h | 14 +++++++++ >> 6 files changed, 173 insertions(+), 14 deletions(-) >> > > [...]
