Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030379AbWBAK3V (ORCPT ); Wed, 1 Feb 2006 05:29:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932408AbWBAK3V (ORCPT ); Wed, 1 Feb 2006 05:29:21 -0500 Received: from aun.it.uu.se ([130.238.12.36]:15579 "EHLO aun.it.uu.se") by vger.kernel.org with ESMTP id S932397AbWBAK3U (ORCPT ); Wed, 1 Feb 2006 05:29:20 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <17376.36154.580526.776564@alkaid.it.uu.se> Date: Wed, 1 Feb 2006 11:28:10 +0100 From: Mikael Pettersson To: Jacek Lipkowski Cc: linux-kernel@vger.kernel.org Subject: Re: patch to make 2.4.32 work on i486 again In-Reply-To: References: X-Mailer: VM 7.17 under Emacs 20.7.1 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1946 Lines: 49 Jacek Lipkowski writes: > Booting the 2.4.32 kernel compiled for a i486 on an i486 box fails, > because "Kernel compiled for Pentium+, requires TSC feature!" (printed > from check_config() include/asm-i386/bugs.h). To reproduce, select 486 in > the kernel configuration and grep CONFIG_X86_TSC .config > > Seems strange that no one noticed this, am i the only one still using 486 > boxes? :) > > Jacek > > Simple patch against vanilla 2.4.32: > > --- arch/i386/config.in.old 2006-01-30 22:57:21.000000000 +0100 > +++ arch/i386/config.in 2006-01-30 23:00:55.000000000 +0100 > @@ -65,6 +65,7 @@ > define_bool CONFIG_X86_POPAD_OK y > define_bool CONFIG_RWSEM_GENERIC_SPINLOCK n > define_bool CONFIG_RWSEM_XCHGADD_ALGORITHM y > + define_bool CONFIG_X86_TSC n > fi > if [ "$CONFIG_M486" = "y" ]; then > define_int CONFIG_X86_L1_CACHE_SHIFT 4 > @@ -72,6 +73,7 @@ > define_bool CONFIG_X86_ALIGNMENT_16 y > define_bool CONFIG_X86_PPRO_FENCE y > define_bool CONFIG_X86_F00F_WORKS_OK n > + define_bool CONFIG_X86_TSC n > fi > if [ "$CONFIG_M586" = "y" ]; then > define_int CONFIG_X86_L1_CACHE_SHIFT 5 This is a known limitation of the 2.4 kernel's configuration system: a single round of make ${foo}config doesn't always reach a fixpoint with regard to the derived options. CONFIG_X86_TSC is the standard example of this: switching from a stable .config with TSC (say i686) to one without (say i486) leaves a stray definition of CONFIG_X86_TSC behind in .config. Solution: run 'make oldconfig' after flipping the user-selectatable options. Your patch may fix the TSC case, but there are probably more cases like this in 2.4. /Mikael - 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/