linux-kernel - Re: [PATCH v3] Documentation: Add section about CPU vulnerabilities for Spectre

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Message-ID: <alpine.DEB.2.21.1906172222430.1963@nanos.tec.linutronix.de>
Date:   Mon, 17 Jun 2019 22:23:39 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Jonathan Corbet <corbet@....net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ben Greear <greearb@...delatech.com>, stable@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Jun Nakajima <jun.nakajima@...el.com>,
        Jiri Kosina <jikos@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Jon Masters <jcm@...hat.com>,
        Waiman Long <longman9394@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Mark Gross <mgross@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>, x86@...nel.org
Subject: Re: [PATCH v3] Documentation: Add section about CPU vulnerabilities
 for Spectre

Tim,

On Mon, 17 Jun 2019, Thomas Gleixner wrote:

> Tim,
> 
> On Mon, 17 Jun 2019, Tim Chen wrote:
> 
> > +Spectre variant 1 attacks take advantage of speculative execution of
> > +conditional branches, while Spectre variant 2 attacks use speculative
> > +execution of indirect branches to leak privileged memory. See [1] [5]
> > +[7] [10] [11].
> 
> It would be great to actually link these [N] to the actual http link at the
> bottom. No idea what's the best way to do that.
> 
> Jonathan?
> 
> > +Mitigation control on the kernel command line
> > +---------------------------------------------
> > +
> > +Spectre variant 2 mitigation can be disabled or force enabled at the
> > +kernel command line.
> 
> The below renders horribly when converted to HTML
> 
> You probably want to wrap these into a table
> 
> > +	nospectre_v2	[X86] Disable all mitigations for the Spectre variant 2
> > +			(indirect branch prediction) vulnerability. System may
> > +			allow data leaks with this option, which is equivalent
> > +			to spectre_v2=off.
> > +
> > +
> > +        spectre_v2=     [X86] Control mitigation of Spectre variant 2
> > +			(indirect branch speculation) vulnerability.
> > +			The default operation protects the kernel from
> > +			user space attacks.
> 
> Maybe Jonathan has a better idea.

But ideally you follow the table style which is used for the L1TF and MDS
command line options.

Thanks,

	tglx