linux-kernel - RE: [PATCH v6: 4/4] x86/cpufeature: Add R3MWAIT to CPU features

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Date:   Thu, 27 Oct 2016 16:46:54 +0000
From:   "Andrejczuk, Grzegorz" <grzegorz.andrejczuk@...el.com>
To:     Borislav Petkov <bp@...e.de>
CC:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "Daniluk, Lukasz" <lukasz.daniluk@...el.com>,
        "Cownie, James H" <james.h.cownie@...el.com>,
        "Pan, Jacob jun" <jacob.jun.pan@...el.com>,
        "Luc, Piotr" <Piotr.Luc@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v6: 4/4] x86/cpufeature: Add R3MWAIT to CPU features

> On Thu, Oct 27, 2016 at 04:02:03PM +0200, Grzegorz Andrejczuk wrote:
> > Add cpu feature for ring 3 monitor/mwait.
> > Set HWCAP2 1st bit during init.
> > 
> > Signed-off-by: Grzegorz Andrejczuk <grzegorz.andrejczuk@...el.com>
> > ---
> >  arch/x86/include/asm/cpufeatures.h | 2 ++
> >  arch/x86/kernel/cpu/intel.c        | 4 ++++
> >  2 files changed, 6 insertions(+)
> > 
> > diff --git a/arch/x86/include/asm/cpufeatures.h 
> > b/arch/x86/include/asm/cpufeatures.h
> > index 92a8308..d430200 100644
> > --- a/arch/x86/include/asm/cpufeatures.h
> > +++ b/arch/x86/include/asm/cpufeatures.h
> > @@ -71,6 +71,8 @@
> >  #define X86_FEATURE_RECOVERY	( 2*32+ 0) /* CPU in recovery mode */
> >  #define X86_FEATURE_LONGRUN	( 2*32+ 1) /* Longrun power control */
> >  #define X86_FEATURE_LRTI	( 2*32+ 3) /* LongRun table interface */
> > +/* Xeon Phi x200 ring 3 MONITOR/MWAIT enabled */
> > +#define X86_FEATURE_PHIR3MWAIT	( 2*32+ 4)
>
> This leaf is for Transmeta CPUs:
>
> /* Transmeta-defined CPU features, CPUID level 0x80860001, word 2 */
>
> is KNL close to some Transmeta design, per chance or so?
>
> I mean, for this to work, it would have to implement CPUID leaf 0x80860001...
>

I was reusing Word 3 as you suggested in patch rev. 1. There was idea to use init_scattered_cpuid_features.
What is good place for this feature?