Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965030AbVKHMsK (ORCPT ); Tue, 8 Nov 2005 07:48:10 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965049AbVKHMsJ (ORCPT ); Tue, 8 Nov 2005 07:48:09 -0500 Received: from mailout1.vmware.com ([65.113.40.130]:49165 "EHLO mailout1.vmware.com") by vger.kernel.org with ESMTP id S965030AbVKHMsI (ORCPT ); Tue, 8 Nov 2005 07:48:08 -0500 Message-ID: <43709E86.8010203@vmware.com> Date: Tue, 08 Nov 2005 04:48:06 -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: Ingo Molnar Cc: Andrew Morton , Chris Wright , Linus Torvalds , Linux Kernel Mailing List , Virtualization Mailing List , "H. Peter Anvin" , Zwane Mwaikambo , Martin Bligh , Pratap Subrahmanyam , Christopher Li , "Eric W. Biederman" Subject: Re: [PATCH 4/21] i386 Broken bios common References: <200511080422.jA84MQxK009859@zach-dev.vmware.com> <20051108071935.GB28201@elte.hu> In-Reply-To: <20051108071935.GB28201@elte.hu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 08 Nov 2005 12:48:08.0167 (UTC) FILETIME=[AB4AEF70:01C5E462] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1241 Lines: 37 Ingo Molnar wrote: >* Zachary Amsden wrote: > > > >> gdt = get_cpu_gdt_table(cpu); >> save_desc_40 = gdt[0x40 / 8]; >>- gdt[0x40 / 8] = bad_bios_desc; >>+ gdt[0x40 / 8] = gdt[GDT_ENTRY_BAD_BIOS_CACHE]; >> >> >> > >i like the cleanup, but wouldnt it be simpler to dedicate GDT entry #8 >to the 0x40 descriptor, and hence be compatible with such broken BIOSes >by default? Right now entry #8 is taken up by TLS segment #2, but we >could change GDT_ENTRY_TLS_MIN from 6 to 9 and push the TLS segments to >entries 9,10,11. [ Could there be any buggy SMM code that relies on >having something at 0x40? ] > > I worry that there could be buggy userspace code that relies on having selector 0x40 - notably Wine. So although I would like to make 0x40 the default, can't be guaranteed. SMM code is safe, since it gets SMRAM mapped in on entry and has descriptor saved state so it can mess with tables as it sees fit without worrying about restoring anything. 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/