This patch set introduces the BPF_F_CPU and BPF_F_ALL_CPUS flags for percpu maps, as the requirement of BPF_F_ALL_CPUS flag for percpu_array maps was discussed in the thread of "[PATCH bpf-next v3 0/4] bpf: Introduce global percpu data"[1]. The goal of BPF_ALL_CPUS flag is to reduce data caching overhead in light skeletons by allowing a single value to be reused across all CPUs. This avoids the M:N problem where M cached values are used to update a map on N CPUs kernel. The BPF_F_CPU flag is accompanied by *flags*-embedded cpu info, which specifies the target CPUs for the operation: * For lookup operations: the flag field alongside cpu info enable querying a value on the specified CPU. * For update operations: the flag field alongside cpu info enable updating value for specified CPU. Links: [1] https://lore.kernel.org/bpf/20250526162146.24429-1-leon.hwang@xxxxxxxxx/ Changes: v2 -> v3: * Address comments from Alexei: * Use BPF_F_ALL_CPUS instead of BPF_ALL_CPUS magic. * Introduce these two cpu flags for all percpu maps. * Address comments from Jiri: * Reduce some unnecessary u32 cast. * Refactor more generic map flags check function. * A code style issue. v2 link: https://lore.kernel.org/bpf/20250805163017.17015-1-leon.hwang@xxxxxxxxx/ v1 -> v2: * Address comments from Andrii: * Embed cpu info as high 32 bits of *flags* totally. * Use ERANGE instead of E2BIG. * Few format issues. RFC v2 -> v1: * Address comments from Andrii: * Use '&=' and '|='. * Replace 'reuse_value' with simpler and less duplication code. * Replace 'ASSERT_FALSE' with two 'ASSERT_OK_PTR's in self test. RFC v1 -> RFC v2: * Address comments from Andrii: * Embed cpu to flags on kernel side. * Change BPF_ALL_CPU macro to BPF_ALL_CPUS enum. * Copy/update element within RCU protection. * Update bpf_map_value_size() including BPF_F_CPU case. * Use zero as default value to get cpu option. * Update documents of APIs to be generic. * Add size_t:0 to opts definitions. * Update validate_map_op() including BPF_F_CPU case. * Use LIBBPF_OPTS instead of DECLARE_LIBBPF_OPTS. Leon Hwang (6): bpf: Introduce internal check_map_flags helper function bpf: Introduce BPF_F_CPU flag for percpu_array maps bpf: Introduce BPF_F_CPU flag for percpu_hash and lru_percpu_hash maps bpf: Introduce BPF_F_CPU flag for percpu_cgroup_storage maps libbpf: Support BPF_F_CPU for percpu maps selftests/bpf: Add cases to test BPF_F_CPU flag include/linux/bpf-cgroup.h | 5 +- include/linux/bpf.h | 58 ++++- include/uapi/linux/bpf.h | 2 + kernel/bpf/arraymap.c | 51 ++-- kernel/bpf/hashtab.c | 111 ++++++--- kernel/bpf/local_storage.c | 47 +++- kernel/bpf/syscall.c | 60 ++--- tools/include/uapi/linux/bpf.h | 2 + tools/lib/bpf/bpf.h | 8 + tools/lib/bpf/libbpf.c | 25 +- tools/lib/bpf/libbpf.h | 21 +- .../selftests/bpf/prog_tests/percpu_alloc.c | 224 ++++++++++++++++++ .../selftests/bpf/progs/percpu_alloc_array.c | 32 +++ 13 files changed, 527 insertions(+), 119 deletions(-) -- 2.50.1
