From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-179.mta1.migadu.com (out-179.mta1.migadu.com [95.215.58.179]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 764CC1DDC3F for ; Wed, 7 Jan 2026 02:25:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.179 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767752738; cv=none; b=H48x8/eYvwPXHMhow3/NbxLkOVELwZ4FdEKdJhWl8j9WzjtXaWyHPHl30VyENvQmEzUvHo+eRo+VvShNMD+pBDOSZjoFirOSSH5gYuzOPE7TbcP8Bw28o6qZ3WBYad2K5Tvqr+d6r8WhtqlEojqoCChwszKJa4nogqIWCLdkzX8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767752738; c=relaxed/simple; bh=0vRCcbQzuhyzsY5zP8fzr5uT5iBniJFP6H3iqCEQIX0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=oJlcjI/zTM8xoq+n94UprvTrpG5ug8hdB3J31eGFu+7L1F+MkzG2mjBivMbLqOKwdy+EqBECgkLiFz1RF7ATt9LwOSx2W9pvjfw7mD8sJB0udAX6kBRmAdEW00rjWps7EoWRFCldrpGem02qCLcvU7hSHQflEBunjHVFYgTomx0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=m9IT6FoS; arc=none smtp.client-ip=95.215.58.179 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="m9IT6FoS" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1767752724; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=GdA5AnhU0z9b+4/S5p1h7+/+hz1N8XlHfnP9/gYMZVQ=; b=m9IT6FoShhzX5yet6jfvUW9WLCjHx6BpjtRShOIq715eI24RHXkuJdb3soBX+zZSHKS1oD DQCEdN4hqgXhw4s9qj1p7OHBy+5lEIkco+vLHumYu+WQQ+GDL7n3Kgozh+11ECIr8PIy8T s3IGn9xMR1gMSTpTMupTREpabi5AzgU= From: Leon Hwang To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Jiri Olsa , Yonghong Song , Song Liu , Eduard Zingerman , Martin KaFai Lau , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Shuah Khan , Jason Xing , Willem de Bruijn , Mykyta Yatsenko , Tao Chen , Kumar Kartikeya Dwivedi , Anton Protopopov , Amery Hung , Tobias Klauser , Rong Tao , dxu@dxuuu.xyz, deso@posteo.net, Leon Hwang , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, kernel-patches-bot@fb.com Subject: [PATCH bpf-next v13 0/7] bpf: Introduce BPF_F_CPU and BPF_F_ALL_CPUS flags for percpu maps Date: Wed, 7 Jan 2026 10:20:15 +0800 Message-ID: <20260107022022.12843-1-leon.hwang@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT 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_F_ALL_CPUS flag is to reduce data caching overhead in light skeletons by allowing a single value to be reused to update values 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 CPU 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@linux.dev/ Changes: v12 -> v13: * No changes, rebased on latest tree. v11 -> v12: * Dropped the v11 changes. * Stabilized the lru_percpu_hash map test by keeping an extra spare entry, which can be used temporarily during updates to avoid unintended LRU evictions. v10 -> v11: * Support the combination of BPF_EXIST and BPF_F_CPU/BPF_F_ALL_CPUS for update operations. * Fix unstable lru_percpu_hash map test using the combination of BPF_EXIST and BPF_F_CPU/BPF_F_ALL_CPUS to avoid LRU eviction (reported by Alexei). v9 -> v10: * Add tests to verify array and hash maps do not support BPF_F_CPU and BPF_F_ALL_CPUS flags. * Address comment from Andrii: * Copy map value using copy_map_value_long for percpu_cgroup_storage maps in a separate patch. v8 -> v9: * Change value type from u64 to u32 in selftests. * Address comments from Andrii: * Keep value_size unaligned and update everywhere for consistency when cpu flags are specified. * Update value by getting pointer for percpu hash and percpu cgroup_storage maps. v7 -> v8: * Address comments from Andrii: * Check BPF_F_LOCK when update percpu_array, percpu_hash and lru_percpu_hash maps. * Refactor flags check in __htab_map_lookup_and_delete_batch(). * Keep value_size unaligned and copy value using copy_map_value() in __htab_map_lookup_and_delete_batch() when BPF_F_CPU is specified. * Update warn message in libbpf's validate_map_op(). * Update comment of libbpf's bpf_map__lookup_elem(). v6 -> v7: * Get correct value size for percpu_hash and lru_percpu_hash in update_batch API. * Set 'count' as 'max_entries' in test cases for lookup_batch API. * Address comment from Alexei: * Move cpu flags check into bpf_map_check_op_flags(). v5 -> v6: * Move bpf_map_check_op_flags() from 'bpf.h' to 'syscall.c'. * Address comments from Alexei: * Drop the refactoring code of data copying logic for percpu maps. * Drop bpf_map_check_op_flags() wrappers. v4 -> v5: * Address comments from Andrii: * Refactor data copying logic for all percpu maps. * Drop this_cpu_ptr() micro-optimization. * Drop cpu check in libbpf's validate_map_op(). * Enhance bpf_map_check_op_flags() using *allowed flags* instead of 'extra_flags_mask'. v3 -> v4: * Address comments from Andrii: * Remove unnecessary map_type check in bpf_map_value_size(). * Reduce code churn. * Remove unnecessary do_delete check in __htab_map_lookup_and_delete_batch(). * Introduce bpf_percpu_copy_to_user() and bpf_percpu_copy_from_user(). * Rename check_map_flags() to bpf_map_check_op_flags() with extra_flags_mask. * Add human-readable pr_warn() explanations in validate_map_op(). * Use flags in bpf_map__delete_elem() and bpf_map__lookup_and_delete_elem(). * Drop "for alignment reasons". v3 link: https://lore.kernel.org/bpf/20250821160817.70285-1-leon.hwang@linux.dev/ 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@linux.dev/ v1 -> v2: * Address comments from Andrii: * Embed cpu info as high 32 bits of *flags* totally. * Use ERANGE instead of E2BIG. * Few format issues. Leon Hwang (7): bpf: Introduce BPF_F_CPU and BPF_F_ALL_CPUS flags bpf: Add BPF_F_CPU and BPF_F_ALL_CPUS flags support for percpu_array maps bpf: Add BPF_F_CPU and BPF_F_ALL_CPUS flags support for percpu_hash and lru_percpu_hash maps bpf: Copy map value using copy_map_value_long for percpu_cgroup_storage maps bpf: Add BPF_F_CPU and BPF_F_ALL_CPUS flags support for percpu_cgroup_storage maps libbpf: Add BPF_F_CPU and BPF_F_ALL_CPUS flags support for percpu maps selftests/bpf: Add cases to test BPF_F_CPU and BPF_F_ALL_CPUS flags include/linux/bpf-cgroup.h | 4 +- include/linux/bpf.h | 35 +- include/uapi/linux/bpf.h | 2 + kernel/bpf/arraymap.c | 29 +- kernel/bpf/hashtab.c | 94 +++-- kernel/bpf/local_storage.c | 27 +- kernel/bpf/syscall.c | 37 +- tools/include/uapi/linux/bpf.h | 2 + tools/lib/bpf/bpf.h | 8 + tools/lib/bpf/libbpf.c | 26 +- tools/lib/bpf/libbpf.h | 21 +- .../selftests/bpf/prog_tests/percpu_alloc.c | 328 ++++++++++++++++++ .../selftests/bpf/progs/percpu_alloc_array.c | 32 ++ 13 files changed, 560 insertions(+), 85 deletions(-) -- 2.52.0