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Date: Mon, 1 Apr 2019 19:03:06 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Tianyu Lan <Tianyu.Lan@...rosoft.com>, Thomas Gleixner <tglx@...utronix.de>, Konrad Wilk <konrad.wilk@...cle.com>, Josh Poimboeuf <jpoimboe@...hat.com>, Mukesh Ojha <mojha@...eaurora.org>, Peter Zijlstra <peterz@...radead.org>, Jiri Kosina <jkosina@...e.cz>, Rik van Riel <riel@...riel.com>, Andy Lutomirski <luto@...nel.org>, Micheal Kelley <michael.h.kelley@...rosoft.com>, "K. Y. Srinivasan" <kys@...rosoft.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Borislav Petkov <bp@...en8.de> Subject: [PATCH 4.9 50/56] x86/smp: Enforce CONFIG_HOTPLUG_CPU when SMP=y 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Gleixner <tglx@...utronix.de> commit bebd024e4815b1a170fcd21ead9c2222b23ce9e6 upstream. 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 <Tianyu.Lan@...rosoft.com> Signed-off-by: Thomas Gleixner <tglx@...utronix.de> Acked-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> Cc: Konrad Wilk <konrad.wilk@...cle.com> Cc: Josh Poimboeuf <jpoimboe@...hat.com> Cc: Mukesh Ojha <mojha@...eaurora.org> Cc: Peter Zijlstra <peterz@...radead.org> Cc: Jiri Kosina <jkosina@...e.cz> Cc: Rik van Riel <riel@...riel.com> Cc: Andy Lutomirski <luto@...nel.org> Cc: Micheal Kelley <michael.h.kelley@...rosoft.com> Cc: "K. Y. Srinivasan" <kys@...rosoft.com> Cc: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Borislav Petkov <bp@...en8.de> Cc: K. Y. Srinivasan <kys@...rosoft.com> Cc: stable@...r.kernel.org Link: https://lkml.kernel.org/r/20190326163811.598166056@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- arch/x86/Kconfig | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2051,14 +2051,8 @@ 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"
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