From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from m16.mail.163.com (m16.mail.163.com [220.197.31.5]) (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 891D3262A6 for ; Wed, 29 Apr 2026 03:42:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.197.31.5 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777434170; cv=none; b=UQVlI4lQ3TtRTFy3NBiW7tnBQcWZB9bnfdrs2msb67YsqegaXVYbk6gnxzw01fhN4bMFzrxhTde//Bbf68vBpE/vVem8BgEfcXIpcJfQVzQtljmHpnfcn3d8A0hbU/p2qUGOGsEsMEgxZLv9V1pUuBXEKoRrljOtCXvr6bjbIf0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777434170; c=relaxed/simple; bh=pqgGuZNpmQTyx0diqLkOF+c4l5MwdtbweECe55lGVpw=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=eu2Bcj8aBtIbb+QD1nw1VI/pjCB5aDMG4Pzr9aIXAGMkJwTxABk/CtxBCCAqxghCIx6v9wAk/G/TQizXZKdGAeMf9jv6eX+FrnxUihoAG+iiWehcNFBp2Wcw+j1pUysXvqZ54upI6WDDR72o/rIH8jCCp5TIbaqXiezwqa0+lMo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com; spf=pass smtp.mailfrom=163.com; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b=aAaWHoJK; arc=none smtp.client-ip=220.197.31.5 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=163.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="aAaWHoJK" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:To:Subject:Date:Message-Id:MIME-Version; bh=81 pMw9DuGj5odbozepX5EzLppomqd0rCqWExnAa9ssc=; b=aAaWHoJKg5elmVnSE/ GBDhmkoJtusYYg9SvgNTNoD21v0TI448CBJ1edBwFdPrTjrcN5Rka2az1kSr6jdu oRkvUBT1A7zW5CkM72fp4h+4FTjBpFfsdvx0h37XJtTiCrEijBkbdOefoAmmCeJo HL76cfy+S9XFi/1icVaMyDN2w= Received: from wmy.localdomain (unknown []) by gzga-smtp-mtada-g0-1 (Coremail) with SMTP id _____wDHbnnnffFpjXyTCQ--.65212S2; Wed, 29 Apr 2026 11:41:38 +0800 (CST) From: w15303746062@163.com To: tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org Cc: hpa@zytor.com, peterz@infradead.org, linux-kernel@vger.kernel.org Subject: [BUG] x86/smpboot: WARN_ON in set_cpu_sibling_map triggered by numa=fake=2 Date: Wed, 29 Apr 2026 11:41:25 +0800 Message-Id: <20260429034125.37368-1-w15303746062@163.com> X-Mailer: git-send-email 2.34.1 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-CM-TRANSID:_____wDHbnnnffFpjXyTCQ--.65212S2 X-Coremail-Antispam: 1Uf129KBjvJXoW7ZF48Jw4xKry5Gr45CF4xCrg_yoW8Wr47pr 4fK3ZxGF4kXFWvvayIqF1xC34akws0yrW5Ga45GF18tas0ya18JFW3ta4fJa4xu3sYqa4Y k3WqgF1rW3W8XF7anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07j70edUUUUU= X-CM-SenderInfo: jzrvjiatxuliiws6il2tof0z/xtbDABJyVmnxffLsQgAA3P Hi x86 maintainers, While fuzzing the v7.0 kernel, I encountered a persistent WARNING in `set_cpu_sibling_map()` during boot when using the `numa=fake=2` command-line parameter. The issue appears to be a logic gap in the topology consistency check. When `numa=fake=N` is used, it artificially divides a single physical package into multiple software NUMA nodes. However, the existing check in `set_cpu_sibling_map()` does not account for this fake NUMA state: if (match_pkg(c, o) && !topology_same_node(c, o)) WARN_ON_ONCE(topology_num_nodes_per_package() == 1); Since `numa=fake` forces `!topology_same_node(c, o)` to be true for CPUs on the same package, the WARN_ON_ONCE is falsely triggered. With `panic_on_warn=1` enabled in many fuzzing and testing environments, this leads to an early boot panic. Here is the relevant part of the crash log: ------------[ cut here ]------------ WARNING: arch/x86/kernel/smpboot.c:698 at set_cpu_sibling_map+0x1206/0x1f20 Modules linked in: CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted 7.0.0 #1 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009) RIP: 0010:set_cpu_sibling_map+0x1206/0x1f20 Call Trace: ap_starting arch/x86/kernel/smpboot.c:196 [inline] start_secondary+0xd8/0x2d0 arch/x86/kernel/smpboot.c:280 common_startup_64+0x13e/0x148 ---[ end trace ]--- I am reporting this to bring it to your attention, as it might require a small adjustment to bypass this strict topology check when `numa=fake` is active. Best regards, Mingyu Wang