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

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Message-ID: <20200902164538.GN1362448@hirez.programming.kicks-ass.net>
Date:   Wed, 2 Sep 2020 18:45:38 +0200
From:   peterz@...radead.org
To:     Feng Tang <feng.tang@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] tools/x86: add kcpuid tool to show raw CPU features

On Thu, Aug 27, 2020 at 03:49:03PM +0800, Feng Tang wrote:
> End users frequently want to know what features their processor
> supports, independent of what the kernel supports.
> 
> /proc/cpuinfo is great. It is omnipresent and since it is provided by
> the kernel it is always as up to date as the kernel. But, it can be
> ambiguous about processor features which can be disabled by the kernel
> at boot-time or compile-time.

Let me once again suggest we use CPUID faulting to 'fix' this.

We really should clear the CPUID bits when the kernel explicitly
disables things.

https://lkml.kernel.org/r/1552431636-31511-18-git-send-email-fenghua.yu@intel.com