linux-kernel - Re: [PATCH] ix86: improve determination of X86_MINIMUM_CPU

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Message-Id: <5049C0100200007800099976@nat28.tlf.novell.com>
Date:	Fri, 07 Sep 2012 08:36:16 +0100
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	<mingo@...e.hu>, <tglx@...utronix.de>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ix86: improve determination of
 X86_MINIMUM_CPU_FAMILY

>>> On 07.09.12 at 09:31, Jan Beulich wrote:
>>>> On 07.09.12 at 09:16, "H. Peter Anvin" <hpa@...or.com> wrote:
> > Erk, this isn't right either.  We're not supposed to include 
> > CPUID-enumerable features here, so X86_CMOV, X86_CMPXCHG64 and X86_TSC 
> > don't belong, and should instead be done via required-features.h.
> 
> Ah, so I got misguided by there already being a CPUID-detectable
> feature here (X86_CMPXCHG64). And by the fact that e.g. having
> M686 (or better) selected is then in fact not expected to have a
> relationship to the value chosen here (worth a comment perhaps).
> 
> Further, the "6" case is then completely pointless - X86_P6_NOP
> depends on X86_64. And with all features the kernel cares about
> that got added with Pentium and later being CPUID-enumerable,
> the "5" case would then be superfluous too.

Plus perhaps the X86_64 line should then also be changed into
"depends on X86_32", as all cared about features on x86-64 are
CPUID-enumerable.

Jan

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