From patchwork Mon Jan 13 15:24:35 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Leon Hwang X-Patchwork-Id: 13937637 Received: from out-187.mta1.migadu.com (out-187.mta1.migadu.com [95.215.58.187]) (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 F2405240233 for ; Mon, 13 Jan 2025 15:25:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.187 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736781908; cv=none; b=SyiwWcw3/yjHwjnGq/QsUz9pOEnjiApeQAbjeDOx6fZNZvu0hPq6vPxgGpgQ37OPfI+adaierrlYZ70lKvz9cN6/tr/Y+Pjdp0894d5wiAZnEmebb8vK5CwLcvO0SWFcCS2IyvYgd9V5jazroIxDsBIOPxXEzqXGKdQyugcwjIY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736781908; c=relaxed/simple; bh=sM+nGxqaufS4FPePXRtAYceRlcGNQiY74X4M/wAGCMI=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=X78pM4xWatcyc/dysV3q8/5j0cWY6AsXtSNM+7D8VXeannNAQcFRHsparvlUK2LGiU3Rmewy9nbiL4RKBaySBG0md9gaQQDIxnvGjHRl6P+q7z61Wyo3o491VzMdpIypLNZtb40EFh+y47HjRFaV95UZKSqnxV7zZZI5ktwPinw= 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=tUFWAT5d; arc=none smtp.client-ip=95.215.58.187 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="tUFWAT5d" 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=1736781903; 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=L/lTBHN9Bo5PEFoov3JojQYOFh+P1Kyr9yxIoyV2k8Q=; b=tUFWAT5d/TSeKbskr8b/3vFl0xb/tMJoOy5E7vgL0HCdUpH4GIbDlZ57yUzarf2JVcBAqm d8YetfsQoyE7CV2ojKLi1HipYs2cno2LDMqnJnObDAIkc63kjR7O3ajMvx9JRRvBlZaaV0 8XlRdtHt4kutuOQVyWsp3dsUJGN3PRE= From: Leon Hwang To: bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, yonghong.song@linux.dev, song@kernel.org, eddyz87@gmail.com, leon.hwang@linux.dev, kernel-patches-bot@fb.com Subject: [RFC PATCH bpf-next 0/2] bpf: Introduce global percpu data Date: Mon, 13 Jan 2025 23:24:35 +0800 Message-ID: <20250113152437.67196-1-leon.hwang@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT X-Patchwork-Delegate: bpf@iogearbox.net X-Patchwork-State: RFC This patch set introduces global per-CPU data, similar to commit 6316f78306c1 ("Merge branch 'support-global-data'"), to reduce restrictions in C for BPF programs. With this enhancement, it becomes possible to define and use global per-CPU variables, much like the DEFINE_PER_CPU() macro in the kernel[0]. The idea stems from the bpflbr project[1], which itself was inspired by retsnoop[2]. During testing of bpflbr on the v6.6 kernel, two LBR (Last Branch Record) entries were observed related to the bpf_get_smp_processor_id() helper. Since commit 1ae6921009e5 ("bpf: inline bpf_get_smp_processor_id() helper"), the bpf_get_smp_processor_id() helper has been inlined on x86_64, reducing the overhead and consequently minimizing these two LBR records. However, the introduction of global per-CPU data offers a more robust solution. By leveraging the percpu_array map and percpu instructions, global per-CPU data can be implemented intrinsically. This feature also facilitates sharing per-CPU information between tail callers and callees or between freplace callers and callees through a shared global per-CPU variable. Previously, this was achieved using a 1-entry percpu map, which this patch set aims to improve upon. Links: [0] https://github.com/torvalds/linux/blob/fbfd64d25c7af3b8695201ebc85efe90be28c5a3/include/linux/percpu-defs.h#L114 [1] https://github.com/Asphaltt/bpflbr [2] https://github.com/anakryiko/retsnoop Leon Hwang (2): bpf: Introduce global percpu data selftests/bpf: Add a case to test global percpu data kernel/bpf/arraymap.c | 39 +++++- kernel/bpf/verifier.c | 45 +++++++ tools/lib/bpf/libbpf.c | 112 ++++++++++++++---- .../bpf/prog_tests/global_data_init.c | 83 ++++++++++++- .../bpf/progs/test_global_percpu_data.c | 21 ++++ 5 files changed, 274 insertions(+), 26 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/test_global_percpu_data.c