From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760286AbXEQWaz (ORCPT ); Thu, 17 May 2007 18:30:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757258AbXEQWas (ORCPT ); Thu, 17 May 2007 18:30:48 -0400 Received: from terminus.zytor.com ([192.83.249.54]:59788 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756921AbXEQWar (ORCPT ); Thu, 17 May 2007 18:30:47 -0400 Message-ID: <464CD4E2.6090402@zytor.com> Date: Thu, 17 May 2007 15:19:14 -0700 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.0 (X11/20070419) MIME-Version: 1.0 To: Simon Arlott CC: Claas Langbehn , LKML , Andrew Morton Subject: Re: This kernel requires the following features not present on the CPU... (on a VIA C7 CPU) References: <464C4A22.7040709@rootdir.de> <464CB726.6090201@simon.arlott.org.uk> <464CB7CC.8030706@zytor.com> <464CD45A.6090902@simon.arlott.org.uk> In-Reply-To: <464CD45A.6090902@simon.arlott.org.uk> X-Enigmail-Version: 0.95.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Simon Arlott wrote: > On 17/05/07 21:15, H. Peter Anvin wrote: >> Simon Arlott wrote: >>> Is it automatic? I have CONFIG_X86_CMPXCHG=y without cx8 showing in >>> cpuinfo, and it appears to work fine. >>> >>> Will your changes needlessly prevent the kernel running? Would I be >>> right in thinking that the kernel is successfully using cmpxchg even >>> though it's considered disabled? I realise people compile kernels for >>> the wrong CPU but preventing them working when it's been chosen >>> correctly seems wrong. >>> >> >> CX8 isn't cmpxchg; it's cmpxchg8b. > > Ok, but I have CONFIG_X86_CMPXCHG64=y too. > OK then, then VIA just masks the CPUID bit as opposed to the instruction. Point still holds. -hpa