From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 20 Dec 2002 05:55:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 20 Dec 2002 05:55:16 -0500 Received: from mailout02.sul.t-online.com ([194.25.134.17]:14804 "EHLO mailout02.sul.t-online.com") by vger.kernel.org with ESMTP id ; Fri, 20 Dec 2002 05:55:14 -0500 Message-ID: <3E02F8E1.70509@slit.de> Date: Fri, 20 Dec 2002 12:02:57 +0100 From: achen@t-online.de (Alexander Achenbach) Reply-To: xela@slit.de User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.1) Gecko/20020913 Debian/1.1-1 X-Accept-Language: en MIME-Version: 1.0 To: davej@suse.de, hpa@zytor.com, linux-kernel@vger.kernel.org Subject: [PATCH] zero-size E820 memory (kernel start-up failure) Content-Type: multipart/mixed; boundary="------------080909030608050905050101" Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org This is a multi-part message in MIME format. --------------080909030608050905050101 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Hi everybody. This patch fixes the Ok, booting the kernel. [hangs] problem with BIOSes that report E820 memory maps with zero-size entries. Among the mainboards affected are EPOX 4G4A+ (presumably) EPOX 4BEA[-R] Chaintech 9EJL . In the past (kernels up to 2.4.20), these mainboards could only boot Linux with explicit 'mem=' boot parameters. Up to 2.4.20, a zero-size E820 memory region (eg 0xa0000 - 0xa0000) reported by the BIOS causes 'sanitize_e820_map' to take the end of this region as the start of another region, producing two overlapping regions extending to the end of addressable memory. If the zero-size region is of a higher type than 'usable RAM' (eg 'reserved'), this causes all memory above the zero-size region to be marked unusable (leaving 640k as of the above example -- the kernel fails to start at all). The patch adds code to remove empty entries before sorting regions. It was generated for a 2.4.20 kernel. Best regards, Alex [ Please send answers to my Reply-To address. I'm not subscribed to the kernel mailing list. ] --------------080909030608050905050101 Content-Type: text/plain; name="nullmem.diff" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="nullmem.diff" diff -ur linux-2.4.20/arch/i386/kernel/setup.c linux-2.4.20-nullmem/arch/i386/kernel/setup.c --- linux-2.4.20/arch/i386/kernel/setup.c Fri Nov 29 00:53:09 2002 +++ linux-2.4.20-nullmem/arch/i386/kernel/setup.c Mon Dec 16 14:52:21 2002 @@ -71,6 +71,9 @@ * CacheSize bug workaround updates for AMD, Intel & VIA Cyrix. * Dave Jones , September, October 2001. * + * Provisions for empty E820 memory regions (reported by certain BIOSes). + * Alex Achenbach , December 2002. + * */ /* @@ -501,7 +504,7 @@ int chgidx, still_changing; int overlap_entries; int new_bios_entry; - int old_nr, new_nr; + int old_nr, new_nr, chg_nr; int i; /* @@ -555,20 +558,24 @@ for (i=0; i < 2*old_nr; i++) change_point[i] = &change_point_list[i]; - /* record all known change-points (starting and ending addresses) */ + /* record all known change-points (starting and ending addresses), + omitting those that are for empty memory regions */ chgidx = 0; for (i=0; i < old_nr; i++) { - change_point[chgidx]->addr = biosmap[i].addr; - change_point[chgidx++]->pbios = &biosmap[i]; - change_point[chgidx]->addr = biosmap[i].addr + biosmap[i].size; - change_point[chgidx++]->pbios = &biosmap[i]; + if (biosmap[i].size != 0) { + change_point[chgidx]->addr = biosmap[i].addr; + change_point[chgidx++]->pbios = &biosmap[i]; + change_point[chgidx]->addr = biosmap[i].addr + biosmap[i].size; + change_point[chgidx++]->pbios = &biosmap[i]; + } } + chg_nr = chgidx; /* true number of change-points */ /* sort change-point list by memory addresses (low -> high) */ still_changing = 1; while (still_changing) { still_changing = 0; - for (i=1; i < 2*old_nr; i++) { + for (i=1; i < chg_nr; i++) { /* if > , swap */ /* or, if current= & last=, swap */ if ((change_point[i]->addr < change_point[i-1]->addr) || @@ -591,7 +598,7 @@ last_type = 0; /* start with undefined memory type */ last_addr = 0; /* start with 0 as last starting address */ /* loop through change-points, determining affect on the new bios map */ - for (chgidx=0; chgidx < 2*old_nr; chgidx++) + for (chgidx=0; chgidx < chg_nr; chgidx++) { /* keep track of all overlapping bios entries */ if (change_point[chgidx]->addr == change_point[chgidx]->pbios->addr) --------------080909030608050905050101--