Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751120AbWIMTIR (ORCPT ); Wed, 13 Sep 2006 15:08:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751121AbWIMTIR (ORCPT ); Wed, 13 Sep 2006 15:08:17 -0400 Received: from gw.goop.org ([64.81.55.164]:46019 "EHLO mail.goop.org") by vger.kernel.org with ESMTP id S1751120AbWIMTIQ (ORCPT ); Wed, 13 Sep 2006 15:08:16 -0400 Message-ID: <450854F3.20603@goop.org> Date: Wed, 13 Sep 2006 11:58:59 -0700 From: Jeremy Fitzhardinge User-Agent: Thunderbird 1.5.0.5 (X11/20060907) MIME-Version: 1.0 To: Linus Torvalds , Ingo Molnar , Andi Kleen , "Eric W. Biederman" , Arjan van de Ven , Zachary Amsden CC: Linux Kernel Mailing List , Michael A Fetterman Subject: Assignment of GDT entries Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1319 Lines: 41 What's the rationale for the current assignment of GDT entries? In particular, this section: * 0 - null * 1 - reserved * 2 - reserved * 3 - reserved * * 4 - unused <==== new cacheline * 5 - unused * * ------- start of TLS (Thread-Local Storage) segments: * * 6 - TLS segment #1 [ glibc's TLS segment ] * 7 - TLS segment #2 [ Wine's %fs Win32 segment ] * 8 - TLS segment #3 * 9 - reserved * 10 - reserved * 11 - reserved What are entries 1-3 and 9-11 reserved for? Must they be unused for some reason, or is there some proposed use that has not been impemented yet? Also, is there a particular reason kernel GDT entries start at 12? Would there be a problem in using either 4 or 5 for a kernel GDT descriptor? I'm asking because I'd like to use one of these entries for the PDA descriptor, so that it is on the same cache line as the TLS descriptors. That way, the entry/exit segment register reloads would still only need to touch two GDT cache lines. Would there be a real problem in doing this? Thanks, J - 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/