From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758842Ab1KVWst (ORCPT ); Tue, 22 Nov 2011 17:48:49 -0500 Received: from mga09.intel.com ([134.134.136.24]:65163 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752565Ab1KVWss (ORCPT ); Tue, 22 Nov 2011 17:48:48 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.67,352,1309762800"; d="scan'208";a="78968731" Date: Tue, 22 Nov 2011 23:00:19 +0000 From: Alan Cox To: Andrew Morton Cc: Alessandro Rubini , fujita.tomonori@lab.ntt.co.jp, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org, giancarlo.asnaghi@st.com, maddalena.brattoli@st.com Subject: Re: a question on DMA and remapping Message-ID: <20111122230019.3304ecdf@bob.linux.org.uk> In-Reply-To: <20111117154729.afa24f07.akpm@linux-foundation.org> References: <20111117233059.GA659@mail.gnudd.com> <20111117154729.afa24f07.akpm@linux-foundation.org> Organization: Intel X-Mailer: Claws Mail 3.7.9 (GTK+ 2.22.0; x86_64-redhat-linux-gnu) Organisation: Intel Corporation UK Ltd, registered no. 1134945 (England), Registered office Pipers Way, Swindon, SN3 1RJ Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Generalising the existing code to cover more cases isn't a bad thing > to do. Others might be able to use it, and they surely won't be able > to use any cloned-and-owned swiotlb.c. If you look on the kernel list there has also been some discussion and work recently towards removing a lot of the duplication between the iommu devices. I think really you need to be an actual iommu instance because in reality you are. Trying to fudge it any other way breaks the moment someone tries to do a device to device DMA transfer because your bus/phys mapping seen from your device and the bus/phys mapping seen from another device into your device do not match as I understand it. Alan