From: Greg KH <gregkh@linuxfoundation.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
Tianyu Lan <Tianyu.Lan@microsoft.com>,
Konrad Wilk <konrad.wilk@oracle.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Mukesh Ojha <mojha@codeaurora.org>,
Peter Zijlstra <peterz@infradead.org>,
Jiri Kosina <jkosina@suse.cz>, Rik van Riel <riel@surriel.com>,
Andy Lutomirski <luto@kernel.org>,
Micheal Kelley <michael.h.kelley@microsoft.com>,
"K. Y. Srinivasan" <kys@microsoft.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Borislav Petkov <bp@alien8.de>,
x86@kernel.org
Subject: Re: [patch 2/2] x86/smp: Enforce CONFIG_HOTPLUG_CPU when SMP=y
Date: Wed, 27 Mar 2019 10:12:51 +0900 [thread overview]
Message-ID: <20190327011251.GB3099@kroah.com> (raw)
In-Reply-To: <20190326163811.598166056@linutronix.de>
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>
next prev parent reply other threads:[~2019-03-27 1:12 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-26 16:36 [patch 0/2] cpu/hotplug: Prevent damage with SMP=y and HOTPLUG_CPU=n Thomas Gleixner
2019-03-26 16:36 ` [patch 1/2] cpu/hotplug: Prevent crash when CPU bringup fails on CONFIG_HOTPLUG_CPU=n Thomas Gleixner
2019-03-27 1:12 ` Greg KH
2019-03-28 12:38 ` [tip:smp/urgent] " tip-bot for Thomas Gleixner
2019-03-26 16:36 ` [patch 2/2] x86/smp: Enforce CONFIG_HOTPLUG_CPU when SMP=y Thomas Gleixner
2019-03-27 1:12 ` Greg KH [this message]
2019-03-28 12:39 ` [tip:smp/urgent] " tip-bot for Thomas Gleixner
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