From nobody Tue Feb 10 04:03:45 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 384AEC6FD20 for ; Tue, 21 Mar 2023 19:41:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229484AbjCUTle (ORCPT ); Tue, 21 Mar 2023 15:41:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33786 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230025AbjCUTl3 (ORCPT ); Tue, 21 Mar 2023 15:41:29 -0400 Received: from mail-wr1-x42f.google.com (mail-wr1-x42f.google.com [IPv6:2a00:1450:4864:20::42f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 53B79574F3 for ; Tue, 21 Mar 2023 12:40:49 -0700 (PDT) Received: by mail-wr1-x42f.google.com with SMTP id t15so14874641wrz.7 for ; Tue, 21 Mar 2023 12:40:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance.com; s=google; t=1679427636; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=XuLu3HGQcjaytP31qHwhZDi8gSxR4JzJz3SEvAV55zo=; b=f2Jpe6Q2tY3Gz7GXpj/6SRsTP1/2EY+sStePEHknHyPHUxW7vMGCIi3haEE+eKVzV4 QxHXFaOm6A1jMa600e1jsjRZ2Hl+D9DQQr0Bgolx3k08dShHr+eiu/5y5bB7KAzrD99x A74GnQ92Y32buwVyIEdp5aKzgQ5tEvOHrd2SrkqmqfwKv5ICTLu1GPaPjiJWttr7ilx+ alkfHz7qtXfU5Ad++n6WadIP8+htGhANDetMan0r+uogeKgOQPqKmkn1HZV9RBV3Hruu ulLcOvl51E6Y2+nBPbaRyk0hBhtVT36fUx02Y/ymgMI+7vPPdXEEA4Fw6J7ivKsDukgV I7+g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1679427636; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=XuLu3HGQcjaytP31qHwhZDi8gSxR4JzJz3SEvAV55zo=; b=hMc6w3DY+iGpyIRjI32ehL2+x5+4+S/heBIwgcNpYVekgxmJxapc8Ou5ehK7rU/W21 vv8/qUXFHCKs0NkwENV3TBWRyAs6S8VmfYLKJkb/u7m0vTESxO1o8pbS8q6gEE7p/XSj aJILlXvUdvcnIhkLvavZbNJMeyPAHE1EFjhdGgH32dXTPXD2M1D8W72JDe+n5l4h062B Ad8zpCfpD96/A8FnIT8cl2RlRxf79Xlz1TBiWM+2MyZaC6xHSm0FvlWVcaFvm0n/J15b 61dQjVW/yzkWcajpSSkfDXbd3xN95MEBY6OR8cPov4DATV2JZ8sMnrOFtd44bVCkMWyv PPCQ== X-Gm-Message-State: AO0yUKU4P9bYXvTXyt36LVEUmKAdYVDGW9v4E/PngKhHvcEhU8rtiT85 vEiQK/P3fk+3jaYiM/F7mzoVfg== X-Google-Smtp-Source: AK7set93rDqxKz1jhUQJozmEtQd/brdxwmcmaY7jZxYpsAisVpj5CU3ge1o6x++mwbpFoVM5MS90fA== X-Received: by 2002:a5d:538c:0:b0:2d0:d73a:7671 with SMTP id d12-20020a5d538c000000b002d0d73a7671mr3066653wrv.22.1679427636150; Tue, 21 Mar 2023 12:40:36 -0700 (PDT) Received: from usaari01.cust.communityfibre.co.uk ([2a02:6b6a:b566:0:7a8a:d679:ba4e:61cf]) by smtp.gmail.com with ESMTPSA id a3-20020adffb83000000b002c561805a4csm12005026wrr.45.2023.03.21.12.40.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Mar 2023 12:40:35 -0700 (PDT) From: Usama Arif To: dwmw2@infradead.org, tglx@linutronix.de, kim.phillips@amd.com, brgerst@gmail.com Cc: piotrgorski@cachyos.org, oleksandr@natalenko.name, arjan@linux.intel.com, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, x86@kernel.org, pbonzini@redhat.com, paulmck@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, rcu@vger.kernel.org, mimoja@mimoja.de, hewenliang4@huawei.com, thomas.lendacky@amd.com, seanjc@google.com, pmenzel@molgen.mpg.de, fam.zheng@bytedance.com, punit.agrawal@bytedance.com, simon.evans@bytedance.com, liangma@liangbit.com, gpiccoli@igalia.com, David Woodhouse Subject: [PATCH v16 2/8] cpu/hotplug: Reset task stack state in _cpu_up() Date: Tue, 21 Mar 2023 19:40:02 +0000 Message-Id: <20230321194008.785922-3-usama.arif@bytedance.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230321194008.785922-1-usama.arif@bytedance.com> References: <20230321194008.785922-1-usama.arif@bytedance.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: David Woodhouse Commit dce1ca0525bf ("sched/scs: Reset task stack state in bringup_cpu()") ensured that the shadow call stack and KASAN poisoning were removed from a CPU's stack each time that CPU is brought up, not just once. This is not incorrect. However, with parallel bringup, an architecture may obtain the idle thread for a new CPU from a pre-bringup stage, by calling idle_thread_get() for itself. This would mean that the cleanup in bringup_cpu() would be too late. Move the SCS/KASAN cleanup to the generic _cpu_up() function instead, which already ensures that the new CPU's stack is available, purely to allow for early failure. This occurs when the CPU to be brought up is in the CPUHP_OFFLINE state, which should correctly do the cleanup any time the CPU has been taken down to the point where such is needed. Signed-off-by: David Woodhouse Reviewed-by: Mark Rutland Tested-by: Mark Rutland [arm64] --- kernel/cpu.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index 6c0a92ca6bb5..43e0a77f21e8 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -591,12 +591,6 @@ static int bringup_cpu(unsigned int cpu) struct task_struct *idle =3D idle_thread_get(cpu); int ret; =20 - /* - * Reset stale stack state from the last time this CPU was online. - */ - scs_task_reset(idle); - kasan_unpoison_task_stack(idle); - /* * Some architectures have to walk the irq descriptors to * setup the vector space for the cpu which comes online. @@ -1383,6 +1377,12 @@ static int _cpu_up(unsigned int cpu, int tasks_froze= n, enum cpuhp_state target) ret =3D PTR_ERR(idle); goto out; } + + /* + * Reset stale stack state from the last time this CPU was online. + */ + scs_task_reset(idle); + kasan_unpoison_task_stack(idle); } =20 cpuhp_tasks_frozen =3D tasks_frozen; --=20 2.25.1