Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262105AbTIRTs3 (ORCPT ); Thu, 18 Sep 2003 15:48:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262115AbTIRTs3 (ORCPT ); Thu, 18 Sep 2003 15:48:29 -0400 Received: from mail.jlokier.co.uk ([81.29.64.88]:58005 "EHLO mail.jlokier.co.uk") by vger.kernel.org with ESMTP id S262105AbTIRTs2 (ORCPT ); Thu, 18 Sep 2003 15:48:28 -0400 Date: Thu, 18 Sep 2003 20:48:00 +0100 From: Jamie Lokier To: Andi Kleen Cc: Linus Torvalds , Nick Piggin , Andrew Morton , linux-kernel@vger.kernel.org, richard.brunner@amd.com Subject: Re: [PATCH] Athlon/Opteron Prefetch Fix for 2.6.0test5 + numbers Message-ID: <20030918194800.GA8572@mail.jlokier.co.uk> References: <20030917202100.GC4723@wotan.suse.de> <20030917211200.GA5997@wotan.suse.de> <20030918153831.GA7548@mail.jlokier.co.uk> <20030918160456.GC7548@mail.jlokier.co.uk> <20030918170629.GC7917@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20030918170629.GC7917@wotan.suse.de> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1253 Lines: 31 Andi Kleen wrote: > > My point is simply that non-zero base GDT segments are possible in > > userspace, and whatever code you add later to add the base should > > be aware of that. > > I don't see how a non standard GDT is possible in user space. The GDT > is only managed by the kernel. 2.6 offers to change it for NPTL, but > that only applies to data segments. I don't see anything in set_thread_area() which restricts them to data segments. Btw, NPTL isn't the only userspace code which uses this function. Admittedly it would be quite odd to use set_thread_area() to create and use a GDT code segment - but given that you can do it, it would be _really_ odd if prefetch instructions gave spurious faults in these segments yet were fixed up elsewhere. > In vm86 mode the user can load a different base without LDT, but that > should not matter here (although it may be better to check for VM86 mode > too) Shouldn't spurious faults in prefetch instructions in vm86 mode be fixed up too? -- Jamie - 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/