Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261398AbVCRAQi (ORCPT ); Thu, 17 Mar 2005 19:16:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261327AbVCRAQi (ORCPT ); Thu, 17 Mar 2005 19:16:38 -0500 Received: from ozlabs.org ([203.10.76.45]:10462 "EHLO ozlabs.org") by vger.kernel.org with ESMTP id S261398AbVCRAQf (ORCPT ); Thu, 17 Mar 2005 19:16:35 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <16954.7656.838769.483631@cargo.ozlabs.ibm.com> Date: Fri, 18 Mar 2005 11:16:40 +1100 From: Paul Mackerras To: Alan Cox Cc: Keir Fraser , Jesse Barnes , akpm@osdl.org, Linux Kernel Mailing List , riel@redhat.com, Ian.Pratt@cl.cam.ac.uk, kurt@garloff.de, Christian.Limpach@cl.cam.ac.uk Subject: Re: [PATCH] Xen/i386 cleanups - AGP bus/phys cleanups In-Reply-To: <1111067594.1213.27.camel@localhost.localdomain> References: <16952.41973.751326.592933@cargo.ozlabs.ibm.com> <200503161406.01788.jbarnes@engr.sgi.com> <29ab1884ee5724e9efcfe43f14d13376@cl.cam.ac.uk> <16953.20279.77584.501222@cargo.ozlabs.ibm.com> <1111067594.1213.27.camel@localhost.localdomain> X-Mailer: VM 7.19 under Emacs 21.3.1 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1110 Lines: 26 Alan Cox writes: > On Iau, 2005-03-17 at 09:34, Paul Mackerras wrote: > > This code needs real physical addresses, which are not the same things > > as bus addresses. > > Not always. The code needs platform specific goodies. We've only never > been burned so far because there isn't a box with an IOMMU and AGPGART > where one maps through the other. That sounds like a good way to make AGP accesses slower. :) Seriously, given that AGP is a technology that is being superseded by PCI Express, I think it's reasonable to look at the range of current implementations to see what we have to cope with. So I don't think it's worth worrying too much about the possibility of GARTs that go through the IOMMU. However, the idea of having phys_to_agp/agp_to_phys (or virt_to_agp/agp_to_virt) sounds like it wouldn't be too much effort, if it would help Xen. Paul. - 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/