linux-kernel - Re: [RFC PATCH] tools/x86: add kcpuid tool to show raw CPU features

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Date:   Wed, 2 Sep 2020 20:19:56 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Feng Tang <feng.tang@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] tools/x86: add kcpuid tool to show raw CPU features

On Wed, Sep 02, 2020 at 10:18:38AM -0700, Dave Hansen wrote:
> All good points.
> 
> Personally, I think I'd be OK if kcpuid _focused_ on single-bit values
> only.  Those are the vast majority of the things that we need from such
> a tool.  I don't think there's nearly as much demand for the topology
> enumeration or TLB structure leaf parsing.
> 
> I also kinda doubt we can come up with a file format off the top of our
> heads that can represent all the ways data is represented in the CPUID
> space.  Single bits, sure.

Yap, agreed.

However, we should try to at least provide for some rudimentary support
for multibit fields in case we decide we need them down the road and
after the fact.

I guess it is enough if the tool dumps them and their meaning - if one
needs further info then one would go do the *actual* CPU documentation
anyway...

Thx.

-- 
Regards/Gruss,
    Boris.

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