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Date: Tue, 10 Nov 2009 21:50:07 +0200 From: Avi Kivity <avi@...hat.com> To: "H. Peter Anvin" <hpa@...or.com> CC: Alan Cox <alan@...rguk.ukuu.org.uk>, 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 08:49 PM, H. Peter Anvin wrote: > >> 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? > Because then user programs would run 20x or more slower than the user expects. Better to terminate early (and teach userspace how to choose the instruction subset correctly). -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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