linux-kernel - Re: [PATCH v3 3/4] Add hwcap2 for x86

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Date:   Thu, 13 Oct 2016 17:36:30 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Grzegorz Andrejczuk <grzegorz.andrejczuk@...el.com>
cc:     mingo@...hat.com, hpa@...or.com, x86@...nel.org, bp@...e.de,
        dave.hansen@...ux.intel.com, linux-kernel@...r.kernel.org,
        lukasz.daniluk@...el.com, james.h.cownie@...el.com,
        jacob.jun.pan@...el.com
Subject: Re: [PATCH v3 3/4] Add hwcap2 for x86

On Thu, 13 Oct 2016, Grzegorz Andrejczuk wrote:

> Add hwcap2 attribute for x86.

Great value in repeating the subject line. And the subject line is crap
because this patch does way more than adding hwcap2 ....

> Reserve 1st bit of HWCAP2 for exposing Xeon Phi ring 3 monitor/mwait.
> With this userspace apps can detect Ring 3 MONITOR/MWAIT instructions.

User space cannot detect the instructions. User space can check whether the
instructions are enabled.

> +/* Kernel enabled Ring 3 MWAIT for Xeon Phi*/
> +#define HWCAP2_PHIR3MWAIT		(1 << 0)
> +/* upto bit 31 free */

Very useful comment, NOT! Stop documenting the obvious.

Thanks,

	tglx