Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758025AbZKJUI4 (ORCPT ); Tue, 10 Nov 2009 15:08:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757979AbZKJUI4 (ORCPT ); Tue, 10 Nov 2009 15:08:56 -0500 Received: from terminus.zytor.com ([198.137.202.10]:52090 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757975AbZKJUIz (ORCPT ); Tue, 10 Nov 2009 15:08:55 -0500 Message-ID: <4AF9C6AB.8080006@zytor.com> Date: Tue, 10 Nov 2009 12:01:47 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.4pre) Gecko/20091014 Fedora/3.0-2.8.b4.fc11 Thunderbird/3.0b4 MIME-Version: 1.0 To: Avi Kivity CC: Alan Cox , Willy Tarreau , Pavel Machek , Matteo Croce , Sven-Haegar Koch , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: i686 quirk for AMD Geode References: <4AF4526B.4060101@zytor.com> <40101cc30911061418w357b74d8i3bf9a9537de052d4@mail.gmail.com> <20091108173708.GF1372@ucw.cz> <40101cc30911080940s18eb26bbg641beeaddbc25c3d@mail.gmail.com> <20091108181016.GB32364@elf.ucw.cz> <20091108193618.GB4186@elf.ucw.cz> <40101cc30911081147j77f7b81o86f2cc5a869aca1f@mail.gmail.com> <20091108195158.GD4186@elf.ucw.cz> <20091108200852.7f2cf092@lxorguk.ukuu.org.uk> <20091110052711.GA15338@1wt.eu> <4AF9020C.90108@zytor.com> <4AF9435F.2070103@redhat.com> <20091110105642.215804e0@lxorguk.ukuu.org.uk> <4AF99E04.8080704@zytor.com> <20091110172454.3c4481f2@lxorguk.ukuu.org.uk> <4AF9B5AB.5010800@zytor.com> <4AF9C3EF.6000705@redhat.com> In-Reply-To: <4AF9C3EF.6000705@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1005 Lines: 25 On 11/10/2009 11:50 AM, Avi Kivity wrote: >> >> 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). > I picked the example carefully: SSE3 is a small set of instructions which probably aren't used very heavily. In that sense, it has *exactly* the same properties as CMOV - if you have the source, you're better off recompiling, but it *might* help you if you happen to only have a binary. What I want people to understand is that this is a *huge* rathole, and it doesn't have any obvious bottom that I can see. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/