From: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
To: David Woodhouse <dwmw@amazon.co.uk>
Cc: arjan@linux.intel.com, tglx@linutronix.de, karahmed@amazon.de,
x86@kernel.org, linux-kernel@vger.kernel.org,
tim.c.chen@linux.intel.com, bp@alien8.de, peterz@infradead.org,
pbonzini@redhat.com, ak@linux.intel.com,
torvalds@linux-foundation.org, gregkh@linux-foundation.org,
dave.hansen@intel.com, ashok.raj@intel.com, mingo@kernel.org
Subject: Re: [PATCH v4 5/7] x86/pti: Do not enable PTI on processors which are not vulnerable to Meltdown
Date: Thu, 25 Jan 2018 15:12:52 +0000 [thread overview]
Message-ID: <20180125151252.735a75ac@alans-desktop> (raw)
In-Reply-To: <1516872189-16577-6-git-send-email-dwmw@amazon.co.uk>
On Thu, 25 Jan 2018 09:23:07 +0000
David Woodhouse <dwmw@amazon.co.uk> wrote:
> Also, for CPUs which don't speculate at all, don't report that they're vulnerable
> to the Spectre variants either.
>
> Leave the cpu_no_meltdown[] match table with just X86_VENDOR_AMD in it for now,
> even though that could be done with a simple comparison, on the assumption that
> we'll have more to add.
>
> Based on suggestions from Dave Hansen and Alan Cox.
Looks good to me. I've been doing some more document spelunking and have
some more stuff for 32bit but not for 64bit capable systems.
X86_VENDOR_NSC, 5
is safe as the MediaGX/Geode doesn't have speculation. However CYRIX,5
isn't because there are a mix of CPU types there.
Most interesting is the Cyrix one. I'm going to have to resurrect my
Cyrix kit because some of the Cyrix processors actually have control bits
to turn on/off the BTB and also the return stack predictor (PCR0 bits 1
and 0 respecively) and no lfence so you need to change system flags
or reload a segment register to force a stall.
Alan
next prev parent reply other threads:[~2018-01-25 15:12 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-25 9:23 [PATCH v4 0/7] Basic Speculation Control feature support David Woodhouse
2018-01-25 9:23 ` [PATCH v4 1/7] x86/cpufeatures: Add CPUID_7_EDX CPUID leaf David Woodhouse
2018-01-25 9:23 ` [PATCH v4 2/7] x86/cpufeatures: Add Intel feature bits for Speculation Control David Woodhouse
2018-01-25 9:23 ` [PATCH v4 3/7] x86/cpufeatures: Add AMD " David Woodhouse
2018-01-25 9:23 ` [PATCH v4 4/7] x86/msr: Add definitions for new speculation control MSRs David Woodhouse
2018-01-25 9:23 ` [PATCH v4 5/7] x86/pti: Do not enable PTI on processors which are not vulnerable to Meltdown David Woodhouse
2018-01-25 9:42 ` Peter Zijlstra
2018-01-25 9:56 ` David Woodhouse
2018-01-25 10:01 ` Thomas Gleixner
2018-01-25 15:12 ` Alan Cox [this message]
2018-01-25 9:23 ` [PATCH v4 6/7] x86/cpufeature: Blacklist SPEC_CTRL on early Spectre v2 microcodes David Woodhouse
2018-01-25 10:43 ` David Woodhouse
2018-01-25 10:54 ` Thomas Gleixner
2018-01-25 11:20 ` David Woodhouse
2018-01-25 11:34 ` Thomas Gleixner
2018-01-25 13:41 ` David Woodhouse
2018-01-25 14:58 ` Thomas Gleixner
2018-01-25 16:16 ` Alan Cox
2018-01-25 16:24 ` Thomas Gleixner
2018-01-25 16:35 ` David Woodhouse
2018-01-26 9:40 ` Ingo Molnar
2018-01-25 9:23 ` [PATCH v4 7/7] x86/speculation: Add basic IBPB (Indirect Branch Prediction Barrier) support David Woodhouse
2018-01-25 11:41 ` Borislav Petkov
2018-01-25 11:47 ` David Woodhouse
2018-01-25 11:50 ` Borislav Petkov
2018-01-25 11:58 ` David Woodhouse
2018-01-25 12:03 ` Borislav Petkov
2018-01-25 12:11 ` David Woodhouse
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