From: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: David Woodhouse <dwmw@amazon.co.uk>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 5/5] x86/pti: Do not enable PTI on fixed Intel processors
Date: Tue, 23 Jan 2018 20:45:52 +0000 [thread overview]
Message-ID: <20180123204552.14040f98@alans-desktop> (raw)
In-Reply-To: <bb364dbb-4f16-56ab-c306-d96edea94dad@citrix.com>
> > static int in_order_cpu(void)
> > {
> > /* Processors with CPU id etc */
> > if (x86_match_cpu(cpu_in_order))
> > return 1;
> > /* Other rules here */
> > return 0;
> > }
>
> Why does in-order vs out-of-order matter?
>
> There are leaky SP3 gadgets which satisfy in-order requirements, so long
> as the processor is capable of speculating 3 instructions past an
> unresolved branch.
>
> What would (at a guess) save an in-order speculative processor from
> being vulnerable is if memory reads are issued and resolve in program
> order, but in that case, it is not the in-order property of the
> processor which makes it safe.
Fair point - I should rename it cpu_speculates(). The atoms in that
list don't speculate.
Alan
[My Cyrix 6x86 had a different kind of meltdown problem....]
next prev parent reply other threads:[~2018-01-23 20:46 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-23 16:52 [PATCH v2 0/5] Basic Speculation Control feature support David Woodhouse
2018-01-23 16:52 ` [PATCH v2 1/5] x86/cpufeatures: Add CPUID_7_EDX CPUID leaf David Woodhouse
2018-01-23 16:52 ` [PATCH v2 2/5] x86/cpufeatures: Add Intel feature bits for Speculation Control David Woodhouse
2018-01-23 18:43 ` Dave Hansen
2018-01-24 1:23 ` Woodhouse, David
2018-01-24 1:28 ` Dave Hansen
2018-01-24 8:13 ` Woodhouse, David
2018-01-23 16:52 ` [PATCH v2 3/5] x86/cpufeatures: Add AMD " David Woodhouse
2018-01-24 8:39 ` Kirill A. Shutemov
2018-01-24 8:40 ` David Woodhouse
2018-01-23 16:52 ` [PATCH v2 4/5] x86/msr: Add definitions for new speculation control MSRs David Woodhouse
2018-01-23 18:27 ` Dave Hansen
2018-01-23 18:31 ` Greg KH
2018-01-23 18:48 ` Woodhouse, David
2018-01-23 16:52 ` [PATCH v2 5/5] x86/pti: Do not enable PTI on fixed Intel processors David Woodhouse
2018-01-23 18:12 ` Andi Kleen
2018-01-24 1:21 ` David Woodhouse
2018-01-23 18:40 ` Dave Hansen
2018-01-24 1:27 ` David Woodhouse
2018-01-23 18:41 ` Dave Hansen
2018-01-23 18:44 ` Woodhouse, David
2018-01-23 18:45 ` Alan Cox
2018-01-23 19:02 ` Andrew Cooper
2018-01-23 20:45 ` Alan Cox [this message]
2018-01-23 20:38 ` Linus Torvalds
2018-01-23 20:50 ` David Woodhouse
2018-01-24 16:25 ` David Woodhouse
2018-01-24 17:07 ` Alan Cox
2018-01-24 17:42 ` David Woodhouse
2018-01-24 18:40 ` Alan Cox
2018-01-24 18:59 ` David Woodhouse
2018-01-24 19:37 ` David Woodhouse
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