Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932364AbVKOEE0 (ORCPT ); Mon, 14 Nov 2005 23:04:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932362AbVKOEE0 (ORCPT ); Mon, 14 Nov 2005 23:04:26 -0500 Received: from mailout1.vmware.com ([65.113.40.130]:17677 "EHLO mailout1.vmware.com") by vger.kernel.org with ESMTP id S932361AbVKOEEZ (ORCPT ); Mon, 14 Nov 2005 23:04:25 -0500 Message-ID: <43795E47.70507@vmware.com> Date: Mon, 14 Nov 2005 20:04:23 -0800 From: Zachary Amsden User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.2) Gecko/20040803 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Rohit Seth Cc: akpm@osdl.org, sfr@canb.auug.org.au, mm-commits@vger.kernel.org, Linux Kernel Mailing List , Stephen Rothwell , sfr@linuxcare.com.au, david@lechnyr.com, kontakt@hanno.de Subject: Does anyone undefine APM_RELAX_SEGMENTS? References: <200511100824.jAA8O0fu008792@shell0.pdx.osdl.net> <1132024003.6760.16.camel@akash.sc.intel.com> In-Reply-To: <1132024003.6760.16.camel@akash.sc.intel.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 15 Nov 2005 04:04:23.0231 (UTC) FILETIME=[A9767CF0:01C5E999] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1709 Lines: 50 Rohit Seth wrote: >On Thu, 2005-11-10 at 00:23 -0800, akpm@osdl.org wrote: > > >>The patch titled >> >> x86: Always relax segments >> >>has been added to the -mm tree. Its filename is >> >> x86-always-relax-segments.patch >> >> >>From: Zachary Amsden >> >>APM BIOSes have many bugs regarding proper representation of the appropriate >>segment limits for calling the BIOS. By default, APM_RELAX_SEGMENTS is always >>turned on to support running the APM BIOS on these buggy machines. Keeping >>64k limits poses very little danger to the kernel, because the pages where the >>APM BIOS is located will always be in low physical memory BIOS areas, which >>should already be marked reserved, and only buggy BIOSes would possibly >>overstep the segment bounds with writes to data anyway. >> >>Since forcing stricter limits breaks many machines and is not default >>behavior, it seems reasonable to deprecate the older code which may cause APM >>BIOS to fault. >> >> >> > >But I presume it make some other machines to work? > > It would make the APM thread panic on machines with broken APM BIOS - which is not very useful except for proving a BIOS bug. But APM is inherently safer than PnP, since there is no transfer segment which can corrupt arbitrary kernel memory. In the history of its introduction, I can not find a single distribution or use which undefines this macro. If anyone knows otherwise, please advise. Zach - 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/