linux-kernel - Re: [PATCH] x86/cpufeatures: Add enumeration for serialize instruction

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Date:   Sat, 4 Apr 2020 10:28:09 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Ricardo Neri <ricardo.neri@...el.com>, x86@...nel.org,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>
Subject: Re: [PATCH] x86/cpufeatures: Add enumeration for serialize
 instruction

On Fri, Apr 03, 2020 at 10:20:39PM -0700, Ricardo Neri wrote:
> Do you mean code in the kernel using this instructions. Thus far, I
> don't have any kernel use cases for this instruction.

I'm sure you can find at least a couple of places in the kernel
which use CPUID to serialize and could switch to this new insn with
alternatives, for example. Or all those memory barrier uses. Would it be
better to switch to SERIALIZE there? Dunno, but would be good to know.
And so on.

> My intention is to expose this instruction to user space via
> /proc/cpuinfo. Is that not acceptable?

I know what your intention is. What good is the string "serialize" in
/proc/cpuinfo if nothing uses it?

-- 
Regards/Gruss,
    Boris.

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