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From: Hugh Dickins <hugh@veritas.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org
Subject: Re: P6 NOPs again: MPSC?
Date: Mon, 10 Mar 2008 22:02:01 +0000 (GMT)	[thread overview]
Message-ID: <Pine.LNX.4.64.0803102142440.2464@blonde.site> (raw)
In-Reply-To: <47D59743.7040709@zytor.com>

On Mon, 10 Mar 2008, H. Peter Anvin wrote:
> Hugh Dickins wrote:
> > 
> > I'm suspecting that the patch below is actually wrong, and that it's
> > really the "(X86_64 || !X86_GENERIC) &&" which should be changed;
> > but very unsure of my ground and what's right for CPU_GENERIC -
> > the 32/64 heritage of x86/Kconfig.cpu rather confuses me.
> 
> X86_64 && !X86_GENERIC comes from not wanting to be a compatibility issue when
> compiling for generic CPUs.  There are some 32-bit otherwise i686-compatible
> chips (from VIA and Transmeta) which don't have these NOPs.

Yup, I realized that (with || in place of &&): I meant that perhaps
it was supposed to say X86_64 || (!X86_GENERIC && (M686 || ....))
since quite a lot of other options there have "|| X86_64" to cover
all the 64-bit possibilities at once i.e. is it only MPSC that
needs to be added, or both MPSC and CPU_GENERIC?

(But I've lost my way around here.  A good example of the 32/64
confusion is how one has to remember that X86_GENERIC is peculiar
to 32-bit, and CPU_GENERIC peculiar to 64-bit.  And CPU_GENERIC is
understandably an alternative to the specific 64-bit models, but
X86_GENERIC is strangely in addition to the specific 32-bit models.)

Hugh

  reply	other threads:[~2008-03-10 22:12 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-03-04 19:33 [PATCH] x86: a P4 is a P6 not an i486 Hugh Dickins
2008-03-04 21:01 ` Ingo Molnar
2008-03-04 21:24   ` H. Peter Anvin
2008-03-04 21:32     ` Ingo Molnar
2008-03-10 19:14     ` P6 NOPs again: MPSC? Hugh Dickins
2008-03-10 20:17       ` H. Peter Anvin
2008-03-10 22:02         ` Hugh Dickins [this message]
2008-03-11  6:43           ` H. Peter Anvin
2008-03-11 14:00             ` Hugh Dickins
2008-03-11  9:28           ` Ingo Molnar
2008-03-11 13:45             ` Hugh Dickins

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