From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264203AbTGBRHl (ORCPT ); Wed, 2 Jul 2003 13:07:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264188AbTGBRGO (ORCPT ); Wed, 2 Jul 2003 13:06:14 -0400 Received: from ns.suse.de ([213.95.15.193]:15364 "EHLO Cantor.suse.de") by vger.kernel.org with ESMTP id S264186AbTGBRGF (ORCPT ); Wed, 2 Jul 2003 13:06:05 -0400 Date: Wed, 2 Jul 2003 19:20:26 +0200 From: Andi Kleen To: Grant Grundler Cc: Andi Kleen , James Bottomley , axboe@suse.de, davem@redhat.com, suparna@in.ibm.com, linux-kernel@vger.kernel.org, alex_williamson@hp.com, bjorn_helgaas@hp.com Subject: Re: [RFC] block layer support for DMA IOMMU bypass mode II Message-ID: <20030702172026.GB32261@wotan.suse.de> References: <1057077975.2135.54.camel@mulgrave> <20030702015701.6007ac26.ak@suse.de> <20030702165510.GC11739@dsl2.external.hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20030702165510.GC11739@dsl2.external.hp.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 02, 2003 at 10:55:10AM -0600, Grant Grundler wrote: > On Wed, Jul 02, 2003 at 01:57:01AM +0200, Andi Kleen wrote: > > The K8 IOMMU cannot support this virtually contiguous thing. The reason > > is that there is no guarantee that an entry in a sglist is a multiple > > of page size. And the aperture can only map 4K sized chunks, like > > a CPU MMU. So e.g. when you have an sglist with multiple 1K entries there is > > no way to get them continuous in IOMMU space (short of copying) > > Can two adjacent IOMMU entries be used to map two 1K buffers? > Assume the 1st buffer ends on a 4k alignment and the next one > starts on a 4k alignment. Yes, it could. But is that situation likely/worth to handle? -Andi