linux-kernel - RE: [PATCH 2/2] x86, Makefile: Add new generic x86-64 settings v2/v3/v4

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Message-ID: <b09a7be32cef407cb6b6361554411bda@AcuMS.aculab.com>
Date:   Thu, 19 Aug 2021 21:58:03 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Christoph Hellwig' <hch@...radead.org>,
        "torvic9@...lbox.org" <torvic9@...lbox.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "clang-built-linux@...glegroups.com" 
        <clang-built-linux@...glegroups.com>,
        "graysky@...hlinux.us" <graysky@...hlinux.us>
Subject: RE: [PATCH 2/2] x86, Makefile: Add new generic x86-64 settings
 v2/v3/v4

From: Christoph Hellwig
> Sent: 18 August 2021 08:15
> 
> On Tue, Aug 17, 2021 at 04:24:48PM +0200, torvic9@...lbox.org wrote:
> > +	  Generic x86-64 CPU.
> > +	  Run equally well on all x86-64 CPUs with min support of x86-64-v2.
> 
> > +	help
> > +	  Generic x86-64-v3 CPU with v3 instructions.
> > +	  Run equally well on all x86-64 CPUs with min support of x86-64-v3.
> > +
> 
> > +	help
> > +	  Generic x86-64 CPU with v4 instructions.
> > +	  Run equally well on all x86-64 CPUs with min support of x86-64-v4.
> 
> How the f&%$% is a user supposed to know what these garbage descriptions
> are supposed to mean?

My thoughts.
I then looked up the link.
Most of the extra instructions are the AVX related ones.
They better not get enabled for a kernel build at all.

I wish I knew whether 'no-avx' actually implied 'no-avx2' and
all later avx options?
Or do kernel builds have to spot each new option and disable
in in turn?

	David

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