linux-kernel - Re: [RFC PATCH 1/3] Documentation/x86: Add documentation for /proc/cpuinfo feature flags

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Message-ID: <8421be21-30ed-02fb-456c-bd3ee3b34f66@intel.com>
Date:   Mon, 15 Jun 2020 11:37:48 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Luck, Tony" <tony.luck@...el.com>, Borislav Petkov <bp@...en8.de>,
        "Park, Kyung Min" <kyung.min.park@...el.com>
Cc:     "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        "Neri, Ricardo" <ricardo.neri@...el.com>,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Subject: Re: [RFC PATCH 1/3] Documentation/x86: Add documentation for
 /proc/cpuinfo feature flags

On 6/15/20 11:31 AM, Luck, Tony wrote:
>> In general, this should say something along the lines that /proc/cpuinfo
>> shows features which the kernel supports.
>>
>> "For a full list of CPUID flags which the CPU supports, use
>> tools/arch/x86/tools/cpuid/cpuid"
>>
>> :-)
> Dave Hansen had suggested (offline) that we add a cpuid tool to the kernel sources.
> 
> I think that's a lot of (duplicated) work for someone to maintain.  The version of this
> tool at http://www.etallen.com/cpuid.html is close to 10K lines of code.

Borislav suggested starting with something as simple as this:

	http://sr71.net/~dave/intel/stupid-cpuid.c

That, plus code that consume the X86_FEATURE_* flag names and print out
what's supported would be pretty handy and way smaller than 10k lines.