From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752977AbZHEXMj (ORCPT ); Wed, 5 Aug 2009 19:12:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752717AbZHEXMi (ORCPT ); Wed, 5 Aug 2009 19:12:38 -0400 Received: from mail-yx0-f175.google.com ([209.85.210.175]:55042 "EHLO mail-yx0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752698AbZHEXMh convert rfc822-to-8bit (ORCPT ); Wed, 5 Aug 2009 19:12:37 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=sn+DoTpOGStPfTlSoJfkTcENMHApQxnhgRzR736beLTB62SODM2CNM/wQTQp8UAyba JudXbIws3hmv1kfL4XjPfEMW7qaj4U6KOn8HoGeYm/0yUppLywuvmYyvSFrDzmZrsjv/ dZmhRIckP8LacNJkhdV3slEGX96zblM5CF1bM= MIME-Version: 1.0 In-Reply-To: <4A79CEEC.9030008@goop.org> References: <1248707041.6100.35.camel@macbook.infradead.org> <21d7e9970907282328l4a44b9a2of4500c5c84a3586b@mail.gmail.com> <1248851712.19733.214.camel@macbook.infradead.org> <21d7e9970907290143q6778511cvda1c6b915f61654a@mail.gmail.com> <1248860205.19733.238.camel@macbook.infradead.org> <4A78C9C6.6010103@goop.org> <1249454696.9324.325.camel@macbook.infradead.org> <21d7e9970908042357m6080e88fyeaaad171888766f2@mail.gmail.com> <4A79CEEC.9030008@goop.org> Date: Thu, 6 Aug 2009 09:12:37 +1000 Message-ID: <21d7e9970908051612v140c2ebfu591e8fe817237889@mail.gmail.com> Subject: Re: [Xen-devel] Re: [RFC] Make AGP work with IOMMU From: Dave Airlie To: Jeremy Fitzhardinge Cc: David Woodhouse , Keir Fraser , xen-devel@lists.xensource.com, Joerg Roedel , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Zhenyu Wang Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 6, 2009 at 4:26 AM, Jeremy Fitzhardinge wrote: > On 08/04/09 23:57, Dave Airlie wrote: >>> All we've done so far is make intel-agp use the DMA API correctly. And >>> that's conditional on CONFIG_DMAR. But we could make it unconditional, >>> and make the other drivers do it too. The code is all fairly generic. >>> >>> Without an IOMMU, the overhead would be fairly minimal. >>> >>> >> >> I'm not sure how prevalent Xen is on AGP systems, I'm going to guess >> not enough that anyone cares. > > What do you mean by AGP here?  Do you mean "machine with physical AGP > port", or "machine with graphics using the AGP aperature"?  There's an > increasing interest in putting Xen on desktop machines, so the former is > debatable, but the latter (I think?) definitely isn't true. > I split my mail along those lines already, an AGP system is one with a physical AGP port, I think you'll probably find a few people still running some Athlons with VIA chipset and radeon 9200s I think, The graphics using AGP-like apertures are only Intel and we've fixed those. >>  Intel integrated chips are the only AGP >> codebase user that are made any more, and they don't really use AGP >> its just a legacy of the previous designs. >> >> > > Plenty of people are using older machines for testing, etc, so I > wouldn't want to exclude them too lightly.  I've got bug reports from > people using older Radeons, etc. My main problem with doing this is getting testing coverage on older systems, if we change all the AGP drivers, the time to find we busted something is probably not until the next major distro release with this code in it. So people can run stuff on 5 year old hardware in 6 months? I'm not sure the gains justify the costs, but if you guys really want to do it I'll take the patch, just be prepared to have it ripped out the minute we get a regression we can't figure out because we haven't got the hw anymore. Dave.