linux-kernel - Re: [PATCH v2] x86, msr: Document AMD "tweak MSRs", use MSR_FnnH

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Message-ID: <20170425162317.pfy6amlgnj2a6xgd@pd.tnic>
Date:   Tue, 25 Apr 2017 18:23:17 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Denys Vlasenko <dvlasenk@...hat.com>
Cc:     Ingo Molnar <mingo@...hat.com>, Andy Lutomirski <luto@...nel.org>,
        Brian Gerst <brgerst@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "H. Peter Anvin" <hpa@...ux.intel.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] x86, msr: Document AMD "tweak MSRs", use
 MSR_FnnH_NAME scheme for them

On Tue, Apr 25, 2017 at 06:15:23PM +0200, Denys Vlasenko wrote:
> On 04/25/2017 06:06 PM, Borislav Petkov wrote:
> > Pls no. Not every MSR for every family. Only the 4 which are actually
> > being used. We can't hold in here the full 32-bit MSR space.
> 
> The replacement of four define names is not the purpose
> of the proposed patch.
> 
> The patch was prompted by the realization that these particular MSRs
> are so badly and inconsistently documented that it takes many hours
> of work and requires reading of literally a dozen PDFs to figure out
> what are their names, which CPUs have them, and what bits are known.

They're all documented in the respective BKDGs or revision guides.

> Anyone who looks at only one document won't see the full picture.

And what is the big picture?

To me it is just a bunch of MSRs. What's so special about them?

> Patch does not document bits, but at least documents all MSR names
> and explains why documentation is so sparse.

No, we don't document MSRs in the kernel - we collect all the MSRs the
kernel uses in msr-index.h.

-- 
Regards/Gruss,
    Boris.

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