From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264087AbTGBAOP (ORCPT ); Tue, 1 Jul 2003 20:14:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264097AbTGBAOP (ORCPT ); Tue, 1 Jul 2003 20:14:15 -0400 Received: from pizda.ninka.net ([216.101.162.242]:44762 "EHLO pizda.ninka.net") by vger.kernel.org with ESMTP id S264087AbTGBAOO (ORCPT ); Tue, 1 Jul 2003 20:14:14 -0400 Date: Tue, 01 Jul 2003 17:21:36 -0700 (PDT) Message-Id: <20030701.172136.48497962.davem@redhat.com> To: ak@suse.de Cc: James.Bottomley@steeleye.com, axboe@suse.de, grundler@parisc-linux.org, 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 From: "David S. Miller" In-Reply-To: <20030702022244.030a8acc.ak@suse.de> References: <20030702015701.6007ac26.ak@suse.de> <20030701.170323.59686965.davem@redhat.com> <20030702022244.030a8acc.ak@suse.de> X-FalunGong: Information control. X-Mailer: Mew version 2.1 on Emacs 21.1 / Mule 5.0 (SAKAKI) 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 From: Andi Kleen Date: Wed, 2 Jul 2003 02:22:44 +0200 On Tue, 01 Jul 2003 17:03:23 -0700 (PDT) "David S. Miller" wrote: > What do you mean? You map only one 4K chunk, and this is used > for all the sub-1K mappings. How should this work when the 1K mappings are spread all over memory? Maybe I'm missing something but from James description it sounds like the block layer assumes that it can pass in a sglist with arbitary elements and get it back remapped to continuous DMA addresses. It assumes it can pass in an sglist with arbitrary "virtually contiguous" elements and get back a continuous DMA address. The BIO_VMERGE_BOUNDRY defines the IOMMU page size and therefore what "virtually contiguous" means.