From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755152AbYIHPYB (ORCPT ); Mon, 8 Sep 2008 11:24:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752899AbYIHPXx (ORCPT ); Mon, 8 Sep 2008 11:23:53 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:57771 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752167AbYIHPXw (ORCPT ); Mon, 8 Sep 2008 11:23:52 -0400 Date: Mon, 8 Sep 2008 17:23:30 +0200 From: Ingo Molnar To: Linus Torvalds Cc: "H. Peter Anvin" , linux@sandersweb.net, linux-kernel@vger.kernel.org, the arch/x86 maintainers , Andi Kleen Subject: Re: [BUG] x86 kenel won't boot under Virtual PC Message-ID: <20080908152330.GA9784@elte.hu> References: <200808311422.12525.linux@sandersweb.net> <200809071922.32974.linux@sandersweb.net> <48C48467.40703@zytor.com> <200809072249.17280.linux@sandersweb.net> <48C4A46B.90705@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Linus Torvalds wrote: > On Sun, 7 Sep 2008, H. Peter Anvin wrote: > > > > Under that logic we shouldn't even have CPU configurables, since you want it > > to "just work" whatever crap you're running on. That is EXACTLY what > > CONFIG_X86_GENERIC means > > I dunno.. Event he help-text doesn't actually agree with that: > > config X86_GENERIC > bool "Generic x86 support" > depends on X86_32 > help > Instead of just including optimizations for the selected > x86 variant (e.g. PII, Crusoe or Athlon), include some more > generic optimizations as well. This will make the kernel > perform better on x86 CPUs other than that selected. > > This is really intended for distributors who need more > generic optimizations. > > Also, quite frankly, while the CPU processor type message says > > The kernel will not necessarily run on earlier architectures than > the one you have chosen, e.g. a Pentium optimized kernel will run on > a PPro, but not necessarily on a i486. > > I thought you agreed that CPU virtualization can be a problem? That > was the whole excuse for why the dynamic code was changed. Why would > it not be true for the static code? > > The fact is, if you want to run on a Core2 or other modern CPU, then > "Virtual PC" is apparently buggy in this respect. You worked around it > for the dynamic choice - but that's totally _pointless_ if you then > don't want to work around it for the static one. yes. X86_P6_NOPS is a totally insignificant optimization and if it makes _any_ CPU not boot (be that virtual or real), then it's frankly not worth it. David, exactly how does the kernel fail to boot with latest -git? (v2.6.27-rc5-313-g64f996f or later) Does detect_nopl() run? It really should, and it should detect the non-working instructions. Ingo