linux-kernel - Re: i686 quirk for AMD Geode

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Message-ID: <4AF9B5AB.5010800@zytor.com>
Date:	Tue, 10 Nov 2009 10:49:15 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	Avi Kivity <avi@...hat.com>, Willy Tarreau <w@....eu>,
	Pavel Machek <pavel@....cz>,
	Matteo Croce <technoboy85@...il.com>,
	Sven-Haegar Koch <haegar@...net.de>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: i686 quirk for AMD Geode

On 11/10/2009 09:24 AM, Alan Cox wrote:
>>
>> In the short term, yes, of course.  However, if we're going to do
>> emulation, we might as well do it right.
> 
> Why is using KVM doing it right ? It sounds like its doing it slowly,
> and hideously memory inefficiently. You are solving an uninteresting
> general case problem when you just need two tiny fixups (or perhaps 3 if
> you want to fix up early x86-64 prefetch)

Why do we only need "two tiny fixups"?  Where do we draw the line in
terms of ISA compatibility?  One could easily argue that the Right
Thing[TM] is to be able to process any optional instruction -- otherwise
one has a very difficult place to draw a line.

Consider SSE3, for example.  Why should the same concept not apply to
SSE3 instructions as to CMOV?
	
	-hpa
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