From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linutronix.de (146.0.238.70:993) by crypto-ml.lab.linutronix.de with IMAP4-SSL for ; 04 Mar 2019 07:31:00 -0000 Received: from mail.kernel.org ([198.145.29.99]) by Galois.linutronix.de with esmtps (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1h0i3u-00039L-AI for speck@linutronix.de; Mon, 04 Mar 2019 08:30:59 +0100 Date: Mon, 4 Mar 2019 08:30:49 +0100 From: Greg KH Subject: [MODERATED] Re: [PATCH RFC 1/4] 1 Message-ID: <20190304073049.GA23573@kroah.com> References: <20190304012138.gikabpafseh2swre@treble> <20190304012322.re2q6n2wjxbwpiin@treble> MIME-Version: 1.0 In-Reply-To: <20190304012322.re2q6n2wjxbwpiin@treble> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit To: speck@linutronix.de List-ID: On Sun, Mar 03, 2019 at 07:23:22PM -0600, speck for Josh Poimboeuf wrote: > From: Josh Poimboeuf > Subject: [PATCH RFC 1/4] x86/speculation/mds: Add mds=full,nosmt cmdline > option > > Add the mds=full,nosmt cmdline option. This is like mds=full, but with > SMT disabled if the CPU is vulnerable. > > Signed-off-by: Josh Poimboeuf > --- > Documentation/admin-guide/hw-vuln/mds.rst | 3 +++ > Documentation/admin-guide/kernel-parameters.txt | 6 ++++-- > arch/x86/kernel/cpu/bugs.c | 10 ++++++++++ > 3 files changed, 17 insertions(+), 2 deletions(-) > > diff --git a/Documentation/admin-guide/hw-vuln/mds.rst b/Documentation/admin-guide/hw-vuln/mds.rst > index 1de29d28903d..244ab47d1fb3 100644 > --- a/Documentation/admin-guide/hw-vuln/mds.rst > +++ b/Documentation/admin-guide/hw-vuln/mds.rst > @@ -260,6 +260,9 @@ time with the option "mds=". The valid arguments for this option are: > > It does not automatically disable SMT. > > + full,nosmt The same as mds=full, with SMT disabled on vulnerable > + CPUs. This is the complete mitigation. While I understand the intention, the number of different combinations we are "offering" to userspace here is huge, and everyone is going to be confused as to what to do. If we really think/say that SMT is a major issue for this, why don't we just have "full" disable SMT? thanks, greg k-h