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SubjectRe: [patch 2/2] x86/smp: Enforce CONFIG_HOTPLUG_CPU when SMP=y
On Tue, Mar 26, 2019 at 05:36:06PM +0100, Thomas Gleixner wrote:
> 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@microsoft.com>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: Konrad Wilk <konrad.wilk@oracle.com>
> Cc: Josh Poimboeuf <jpoimboe@redhat.com>
> Cc: Mukesh Ojha <mojha@codeaurora.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Jiri Kosina <jkosina@suse.cz>
> Cc: Rik van Riel <riel@surriel.com>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Micheal Kelley <michael.h.kelley@microsoft.com>
> Cc: K. Y. Srinivasan <kys@microsoft.com>
> Cc: Greg KH <gregkh@linuxfoundation.org>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: stable@vger.kernel.org
> ---
> arch/x86/Kconfig | 8 +-------
> 1 file changed, 1 insertion(+), 7 deletions(-)

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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