linux-kernel - Re: [PATCH v3 08/10] x86/setcpuid: Add kernel option setcpuid

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Date:   Tue, 5 Feb 2019 09:48:57 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Ingo Molnar <mingo@...hat.com>, H Peter Anvin <hpa@...or.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Michael Chan <michael.chan@...adcom.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        Ricardo Neri <ricardo.neri@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH v3 08/10] x86/setcpuid: Add kernel option setcpuid

On Mon, Feb 04, 2019 at 12:46:30PM -0800, Dave Hansen wrote:
> So, the compromise we reached in this case is that Intel will fully
> document the future silicon architecture, and then write the kernel
> implementation to _that_.  Then, for the weirdo deployments where this
> feature is not enumerated, we have the setcpuid= to fake the enumeration
> in software.

What user is _EVER_ going to use this? Nobody, I expect the answer to
be.

Is this some transient state; where a few (early) models will not have
the enumeration sorted but all later models will have it all neat and
tidy?

If so, we can easily do the FMS solution for this.

But a cmdline features thing is not something I can see anybody but
a limited set of developers ever using.