linux-kernel - Intel FSGSBASE support (was: Re: [PATCH 6/8] x86: Enumerate kernel FSGS capability in AT

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Message-ID: <20150411083526.GA16060@gmail.com>
Date:	Sat, 11 Apr 2015 10:35:26 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Andi Kleen <andi@...stfloor.org>, x86@...nel.org, luto@...nel.org,
	linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Andy Lutomirski <luto@...capital.net>
Subject: Intel FSGSBASE support (was: Re: [PATCH 6/8] x86: Enumerate kernel
 FSGS capability in AT_HWCAP2)


* Borislav Petkov <bp@...en8.de> wrote:

> On Sat, Apr 11, 2015 at 01:08:48AM +0200, Andi Kleen wrote:

> > > > +/* HWCAP2 supplies kernel enabled CPU feature, so that the application
> > > > +   can know that it can safely use them. The bits are defined in
> > > > +   uapi/asm/hwcap.h. */
> > >
> > > Comments formatting.
> >
> > The formatting matches all the other comments in the file.
>
> That doesn't mean you need to add new comments with the old 
> formatting which we're trying to get rid of.

Exactly, and the thing is, I've seen this behavior before, so I'm also 
going to ignore all these Intel FSGSBASE patches from Andi Kleen, for 
the following technical reasons:

 - they are poorly written,

 - a necessary precondition of such features is the thorough (and
   constructively conducted) clean-up of the underlying code,

 - the series exposes a new user-space ABI that is going to be exposed
   forever and has to be done right on the first attempt,

 - unacceptable passive-aggressive behavior was directed by Andi
   against constructive, technical feedback from reviewers and
   maintainers.

So consider Intel FSGSBASE support NACK-ed on these four technical 
grounds. All four problems have to be properly addressed (beyond 
addressing all the other feedback that was given) before the NACK is 
lifted.

Maybe someone else has the time to pick up and deobfuscate (or 
entirely rewrite) these patches into a properly written series?

The Intel FSGSBASE hardware feature itself looks potentially useful, 
so I'm not opposed to the concept itself.

Thanks,

	Ingo
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