Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757842AbXEXJ4a (ORCPT ); Thu, 24 May 2007 05:56:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755679AbXEXJ4W (ORCPT ); Thu, 24 May 2007 05:56:22 -0400 Received: from outpipe-village-512-1.bc.nu ([81.2.110.250]:48933 "EHLO the-village.bc.nu" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1755761AbXEXJ4V (ORCPT ); Thu, 24 May 2007 05:56:21 -0400 Date: Thu, 24 May 2007 10:57:19 +0100 From: Alan Cox To: Paul Mackerras Cc: Christoph Lameter , Russell King , KAMEZAWA Hiroyuki , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, jens.axboe@oracle.com Subject: Re: Define CONFIG_BOUNCE to avoid useless inclusion of bounce buffer logic. Message-ID: <20070524105719.624e43b9@the-village.bc.nu> In-Reply-To: <18005.2746.374990.29287@cargo.ozlabs.ibm.com> References: <20070522133906.ae9c362a.kamezawa.hiroyu@jp.fujitsu.com> <20070523140702.GA16972@flint.arm.linux.org.uk> <18005.2746.374990.29287@cargo.ozlabs.ibm.com> X-Mailer: Claws Mail 2.9.1 (GTK+ 2.10.8; i386-redhat-linux-gnu) Organization: Red Hat UK Cyf., Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, Y Deyrnas Gyfunol. Cofrestrwyd yng Nghymru a Lloegr o'r rhif cofrestru 3798903 Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 820 Lines: 18 > Also there is the problem that some drivers use ZONE_DMA allocations > because their device can only generate addresses below some limit, but > on a platform with an IOMMU there is in fact no restriction on what > memory the device can access. Bzzzzzt - have to call your bluff on that one The IOMMU mapping window itself may be out of range of some devices. This is a big problem on AMD64 where the GART window is above the 2GB boundary - you can do 64->32 nicely but 32->31/30/28/24, all of which turn up on PC hardware, are no solved by the IOMMU only by GFP_DMA Alan - 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/