From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750885AbWDKUwo (ORCPT ); Tue, 11 Apr 2006 16:52:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750918AbWDKUwo (ORCPT ); Tue, 11 Apr 2006 16:52:44 -0400 Received: from e4.ny.us.ibm.com ([32.97.182.144]:64186 "EHLO e4.ny.us.ibm.com") by vger.kernel.org with ESMTP id S1750882AbWDKUwn (ORCPT ); Tue, 11 Apr 2006 16:52:43 -0400 Message-ID: <443C1735.8080600@de.ibm.com> Date: Tue, 11 Apr 2006 22:53:09 +0200 From: Carsten Otte Reply-To: carsteno@de.ibm.com Organization: IBM Deutschland User-Agent: Debian Thunderbird 1.0.7 (X11/20051017) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Linus Torvalds CC: carsteno@de.ibm.com, Jes Sorensen , Andrew Morton , linux-kernel@vger.kernel.org, Hugh Dickins , Nick Piggin , bjorn_helgaas@hp.com Subject: Re: [patch] do_no_pfn handler References: <443BCA98.1020805@de.ibm.com> <443C0B8F.7010501@de.ibm.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Linus Torvalds wrote: > Now, the kernel page table accessor macros are certainly generic enough > that you could have your own "COW bits" macro, and make this all an > architecture-specific feature (and simply not allow it on architectures > that don't have a sw-usable COW bit) > > It so happens that S390 seems to be one of the very few architectures that > doesn't have room for that bit in its regular page table layout, and > that's arguably a design problem for S390. But you _could_ just allocate > extra memory for page tables, and put the COW bit there. The VM wouldn't > care - at that point it would fit in the "larger picture" of just having > the COW information directly in the page tables (even if the "page tables" > would be partly just sw-defined). Interresting idea. Sounds more feasible then splitting vmas, I am going to think about it. Thanks! -- Carsten Otte IBM Linux technology center ARCH=s390