From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B514CC43381 for ; Tue, 26 Mar 2019 16:40:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8E6442075D for ; Tue, 26 Mar 2019 16:40:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732026AbfCZQkK (ORCPT ); Tue, 26 Mar 2019 12:40:10 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:48825 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731489AbfCZQj7 (ORCPT ); Tue, 26 Mar 2019 12:39:59 -0400 Received: from localhost ([127.0.0.1] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1h8p7D-0001bO-Rr; Tue, 26 Mar 2019 17:39:56 +0100 Message-Id: <20190326163811.598166056@linutronix.de> User-Agent: quilt/0.65 Date: Tue, 26 Mar 2019 17:36:06 +0100 From: Thomas Gleixner To: LKML Cc: Tianyu Lan , Konrad Wilk , Josh Poimboeuf , Mukesh Ojha , Peter Zijlstra , Jiri Kosina , Rik van Riel , Andy Lutomirski , Micheal Kelley , "K. Y. Srinivasan" , Greg KH , Linus Torvalds , Borislav Petkov , x86@kernel.org Subject: [patch 2/2] x86/smp: Enforce CONFIG_HOTPLUG_CPU when SMP=y References: <20190326163604.348882514@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The SMT disable 'nosmt' command line argument is not working properly when CONFIG_HOTPLUG_CPU is disabled. The teardown of the sibling CPUs which are required to be brought up due to the MCE issues, cannot work. The CPUs are then kept in a half dead state. As the 'nosmt' functionality has become popular due to the speculative hardware vulnerabilities, the half torn down state is not a proper solution to the problem. Enforce CONFIG_HOTPLUG_CPU=y when SMP is enabled so the full operation is possible. Reported-by: Tianyu Lan Signed-off-by: Thomas Gleixner Cc: Konrad Wilk Cc: Josh Poimboeuf Cc: Mukesh Ojha Cc: Peter Zijlstra Cc: Jiri Kosina Cc: Rik van Riel Cc: Andy Lutomirski Cc: Micheal Kelley Cc: K. Y. Srinivasan Cc: Greg KH Cc: Linus Torvalds Cc: Borislav Petkov Cc: stable@vger.kernel.org --- arch/x86/Kconfig | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2217,14 +2217,8 @@ config RANDOMIZE_MEMORY_PHYSICAL_PADDING If unsure, leave at the default value. config HOTPLUG_CPU - bool "Support for hot-pluggable CPUs" + def_bool y depends on SMP - ---help--- - Say Y here to allow turning CPUs off and on. CPUs can be - controlled through /sys/devices/system/cpu. - ( Note: power management support will enable this option - automatically on SMP systems. ) - Say N if you want to disable CPU hotplug. config BOOTPARAM_HOTPLUG_CPU0 bool "Set default setting of cpu0_hotpluggable"