From: Tom Li <tomli@tomli.me>
To: Roman Mamedov <rm@romanrm.net>
Cc: wireguard@lists.zx2c4.com
Subject: Re: Logical cores / SMT with WireGuard
Date: Mon, 18 Feb 2019 04:44:02 +0800 [thread overview]
Message-ID: <20190217204401.GA26054@localhost.localdomain> (raw)
In-Reply-To: <20190217160136.6138076b@natsu>
On Sun, Feb 17, 2019 at 04:01:36PM +0500, Roman Mamedov wrote:
> On Thu, 14 Feb 2019 18:02:26 +0000
> Lee Yates <rainmakerraw@icloud.com> wrote:
>
> Sorry, hit "send" before reading the rest of your message.
>
> > the router runs headless and is awkward to get a monitor to so I can access
> > the BIOS.
>
> You can toggle it without needing the BIOS.
> It is possible to disable SMT from grub, with Linux kernel boot arguments.
> It even seems possible to disable/enable it without a reboot.
> See https://www.golinuxhub.com/2018/01/how-to-disable-or-enable-hyper.html
Hi all.
The information provided by the original link is out-of-date, it works, but
it's tedious and easy to make a mistake and disable the wrong logical CPU. The
new Linux kernel with L1TF fixes has introduced a SMT kill switch, which is the
standard interface to control SMT.
It's located at
/sys/devices/system/cpu/smt/control
You can disable SMT by,
echo "off" > /sys/devices/system/cpu/smt/control
enable it by,
echo "on" > /sys/devices/system/cpu/smt/control
Or permanently disable it until reboot,
echo "forceoff" > /sys/devices/system/cpu/smt/control.
More information is available at,
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/admin-guide/l1tf.rst
I hope it helps.
Cheers,
Tom Li
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prev parent reply other threads:[~2019-02-17 20:44 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-14 18:02 Logical cores / SMT with WireGuard Lee Yates
2019-02-17 10:54 ` Roman Mamedov
2019-02-17 11:01 ` Roman Mamedov
2019-02-17 20:44 ` Tom Li [this message]
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