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From: David Woodhouse <dwmw2@infradead.org>
To: Tom Lendacky <thomas.lendacky@amd.com>, Borislav Petkov <bp@alien8.de>
Cc: x86-ml <x86@kernel.org>,
	linux-tip-commits@vger.kernel.org, hpa@zytor.com,
	 gregkh@linuxfoundation.org, tglx@linutronix.de,
	linux-kernel@vger.kernel.org,  mingo@kernel.org
Subject: Re: [PATCH] x86/cpufeatures: Cleanup AMD speculation feature bits
Date: Sat, 27 Jan 2018 08:49:42 +0000	[thread overview]
Message-ID: <1517042982.30244.302.camel@infradead.org> (raw)
In-Reply-To: <2cea933f-7e06-26d5-95cf-41df8308a0f8@amd.com>

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On Fri, 2018-01-26 at 17:14 -0600, Tom Lendacky wrote:
> On 1/26/2018 4:10 PM, Borislav Petkov wrote:
> > 
> > On Fri, Jan 26, 2018 at 09:59:44PM +0000, David Woodhouse wrote:
> > > 
> > > If we wanted to do this kind of thing, we'd do it the other way round.
> > > Turn the *Intel* feature into both 'IBRS' and 'IBPB' CPU-visible
> > > features, and have those defined in the AMD word.
> > You lost me here: have those defined in the AMD word?
> > 
> > > 
> > > Then use virtual bits with "" for the software features, since we
> > > don't want *those* to appear in /proc/cpuinfo.
> > Whatever we do, I think it would be most consistent to have three
> > strings, *both* on Intel and AMD visible in cpuinfo: "ibrs", "ibpb" and
> > "stibp" so that there's no confusion what is enabled on each box.
> > 
> > Now, those three can be the *virtual* features which get set by the
> > actual CPUID features on init. And the latter, the *actual* CPUID
> > features don't need to be visible in cpuinfo: people shouldn't care
> > whether "spec_ctrl" on Intel and "pred_cmd" on AMD both mean "ibpb". It
> > should be simply "ibpb" on both vendors in cpuinfo.
> > 
> > Ditto for the others.
> > 
> > This way you have one unified message of what is enabled on *any* box.
> That sounds good to me.

Yes, that's what I meant. Expose "ibpb", "ibrs" and "stibp" in
/proc/cpuinfo, which happen to line up with what's in the AMD CPUID
word so let's use the AMD ones as the visible ones.

The Intel bits just will set those. I'll do that now...

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  reply	other threads:[~2018-01-27  8:49 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-25 16:14 [PATCH v5 0/7] Basic Speculation Control feature support David Woodhouse
2018-01-25 16:14 ` [PATCH v5 1/7] x86/cpufeatures: Add CPUID_7_EDX CPUID leaf David Woodhouse
2018-01-26 14:59   ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-25 16:14 ` [PATCH v5 2/7] x86/cpufeatures: Add Intel feature bits for Speculation Control David Woodhouse
2018-01-26 15:00   ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-25 16:14 ` [PATCH v5 3/7] x86/cpufeatures: Add AMD " David Woodhouse
2018-01-25 21:30   ` Borislav Petkov
2018-01-25 21:37     ` Thomas Gleixner
2018-01-25 21:41     ` Borislav Petkov
2018-01-26 15:00   ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-26 18:41     ` [PATCH] x86/cpufeatures: Cleanup AMD speculation feature bits Borislav Petkov
2018-01-26 18:45       ` David Woodhouse
2018-01-26 18:49         ` Borislav Petkov
2018-01-26 21:06           ` Tom Lendacky
2018-01-26 21:52             ` Borislav Petkov
2018-01-26 21:59               ` David Woodhouse
2018-01-26 22:10                 ` Borislav Petkov
2018-01-26 23:14                   ` Tom Lendacky
2018-01-27  8:49                     ` David Woodhouse [this message]
2018-01-27  9:27                     ` David Woodhouse
2018-01-27  9:37                       ` Borislav Petkov
2018-01-27 10:32                         ` David Woodhouse
2018-01-27 13:18                           ` Borislav Petkov
2018-01-25 16:14 ` [PATCH v5 4/7] x86/msr: Add definitions for new speculation control MSRs David Woodhouse
2018-01-26 15:00   ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-25 16:14 ` [PATCH v5 5/7] x86/pti: Do not enable PTI on processors which are not vulnerable to Meltdown David Woodhouse
2018-01-25 18:10   ` Dave Hansen
2018-01-25 19:53     ` Dave Hansen
2018-01-25 22:00   ` Borislav Petkov
2018-01-26 15:01   ` [tip:x86/pti] x86/pti: Do not enable PTI on CPUs " tip-bot for David Woodhouse
2018-01-25 16:14 ` [PATCH v5 6/7] x86/cpufeature: Blacklist SPEC_CTRL/PRED_CMD on early Spectre v2 microcodes David Woodhouse
2018-01-26 15:01   ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-25 16:14 ` [PATCH v5 7/7] x86/speculation: Add basic IBPB (Indirect Branch Prediction Barrier) support David Woodhouse
2018-01-26 15:02   ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-26 16:18     ` David Woodhouse
2018-01-26 21:36   ` [PATCH v5 7/7] " Tim Chen

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