From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 3 May 2002 02:38:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 3 May 2002 02:38:11 -0400 Received: from penguin.e-mind.com ([195.223.140.120]:9508 "EHLO penguin.e-mind.com") by vger.kernel.org with ESMTP id ; Fri, 3 May 2002 02:38:09 -0400 Date: Fri, 3 May 2002 08:38:49 +0200 From: Andrea Arcangeli To: "Martin J. Bligh" Cc: William Lee Irwin III , Daniel Phillips , Russell King , linux-kernel@vger.kernel.org Subject: Re: Bug: Discontigmem virt_to_page() [Alpha,ARM,Mips64?] Message-ID: <20020503083849.Y11414@dualathlon.random> In-Reply-To: <20020502180632.I11414@dualathlon.random> <3972036796.1020330599@[10.10.2.3]> <20020502184037.J11414@dualathlon.random> <20020502171655.GJ32767@holomorphy.com> <20020502204136.M11414@dualathlon.random> <20020502191903.GL32767@holomorphy.com> <148490000.1020378039@flay> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.3.22.1i X-GnuPG-Key-URL: http://e-mind.com/~andrea/aa.gnupg.asc X-PGP-Key-URL: http://e-mind.com/~andrea/aa.asc Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 02, 2002 at 03:20:39PM -0700, Martin J. Bligh wrote: > > On Thu, May 02, 2002 at 08:41:36PM +0200, Andrea Arcangeli wrote: > >> but can you plugin 32bit pci hardware into your 64bit-pci slots, right? > >> If not, and if you're also sure the linux drivers for your hardware are all > >> 64bit-pci capable then you can do the changes regardless of the 4G > >> limit, in such case you can spread the direct mapping all over the whole > >> 64G physical ram, whereever you want, no 4G constraint anymore. > > > > I believe 64-bit PCI is pretty much taken to be a requirement; if it > > weren't the 4GB limit would once again apply and we'd be in much > > trouble, or we'd have to implement a different method of accommodating > > limited device addressing capabilities and would be in trouble again. > > IIRC, there are some funny games you can play with 32bit PCI DMA. > You're not necessarily restricted to the bottom 4Gb of phys addr space, > you're restricted to a 4Gb window, which you can shift by programming > a register on the card. Fixing that register to point to a window for the > node in question allows you to allocate from a node's pg_data_t and > assure DMAable RAM is returned. if you've as many windows as the number of nodes than you're just fine in all cases. you only need to teach pci_map_single and friends to return the right bus address that won't be an identity anymore with the phys addr, then you can forget the >4G phys constraint on the pages returned by zone_normal :). Andrea