From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754001AbYIHQIU (ORCPT ); Mon, 8 Sep 2008 12:08:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752389AbYIHQIL (ORCPT ); Mon, 8 Sep 2008 12:08:11 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:51931 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752254AbYIHQIK (ORCPT ); Mon, 8 Sep 2008 12:08:10 -0400 Date: Mon, 8 Sep 2008 09:07:41 -0700 (PDT) From: Linus Torvalds To: "H. Peter Anvin" cc: Andi Kleen , 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 In-Reply-To: <48C54839.8050304@zytor.com> Message-ID: References: <200808311422.12525.linux@sandersweb.net> <200809071922.32974.linux@sandersweb.net> <48C48467.40703@zytor.com> <200809072249.17280.linux@sandersweb.net> <48C4A46B.90705@zytor.com> <20080908154535.GL26079@one.firstfloor.org> <48C54839.8050304@zytor.com> User-Agent: Alpine 1.10 (LFD 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 8 Sep 2008, H. Peter Anvin wrote: > > The help text is indeed out of date. I did a patch yesterday to, among other > things, update it; I also want to verify that we are disabling all options > that can cause gcc or binutils to generate nopl's; I plan to push it today. Peter. The help text may be out of date because of changes to NOPL usage, but you should ask yourself whether the change is actually a _good_ change. IOW, I really don't see why you are pushing changing the help-text, instead of just making the kernel work better. The fact that some broken gcc/binutils versions may screw us over _anyway_ may well mean that we should just push back on _that_ change instead. Quite frankly, from a user perspective, even a very _technical_ one, please tell me what the advantage of not being fairly generic by default is. Really. Yes, there are some _big_ ISA issues where it is worth doing real static code selection (as opposed to just instruction selection and scheduling etc that still _works_ for everybody, but optimizes for certain archtiectures). So things like cmpxchg/xadd (for atomics) and cmov (for compiler-generated code), and bswap (for networking) can really make a big difference, and are not really realistic to do dynamically. But NOPL? That's simply not _worth_ it being painful over. And the fact is, the current help text describes (a) the historical meaning (optimize for a specific architecture, but don't make extreme choices that are bad for others) (b) what people would generally _want_. and I really don't think that changing the help text is the right solution here. It may be "technically correct", but it is simply not user-friendly or smart. Linus