Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754655Ab0G2Ihu (ORCPT ); Thu, 29 Jul 2010 04:37:50 -0400 Received: from tx2ehsobe004.messaging.microsoft.com ([65.55.88.14]:22097 "EHLO TX2EHSOBE007.bigfish.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750938Ab0G2Ihr (ORCPT ); Thu, 29 Jul 2010 04:37:47 -0400 X-SpamScore: -33 X-BigFish: VPS-33(zz1432N9370J98dN1447Rzz1202hzz15d4Rz32i87h2a8h43h62h) X-Spam-TCS-SCL: 1:0 X-FB-DOMAIN-IP-MATCH: fail X-WSS-ID: 0L6B9AO-02-2OA-02 X-M-MSG: Date: Thu, 29 Jul 2010 10:40:19 +0200 From: "Roedel, Joerg" To: Arnd Bergmann CC: FUJITA Tomonori , "stepanm@codeaurora.org" , "linux-arm-kernel@lists.infradead.org" , "linux-arm-msm@vger.kernel.org" , "dwalker@codeaurora.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 1/2] arm: msm: Add System MMU support. Message-ID: <20100729084018.GM26098@amd.com> References: <20100729123512Y.fujita.tomonori@lab.ntt.co.jp> <201007291026.55928.arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <201007291026.55928.arnd@arndb.de> Organization: Advanced Micro Devices =?iso-8859-1?Q?GmbH?= =?iso-8859-1?Q?=2C_Karl-Hammerschmidt-Str=2E_34=2C_85609_Dornach_bei_M=FC?= =?iso-8859-1?Q?nchen=2C_Gesch=E4ftsf=FChrer=3A_Thomas_M=2E_McCoy=2C_Giuli?= =?iso-8859-1?Q?ano_Meroni=2C_Andrew_Bowd=2C_Sitz=3A_Dornach=2C_Gemeinde_A?= =?iso-8859-1?Q?schheim=2C_Landkreis_M=FCnchen=2C_Registergericht_M=FCnche?= =?iso-8859-1?Q?n=2C?= HRB Nr. 43632 User-Agent: Mutt/1.5.20 (2009-06-14) X-Reverse-DNS: unknown Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1890 Lines: 43 On Thu, Jul 29, 2010 at 04:26:55AM -0400, Arnd Bergmann wrote: > On Thursday 29 July 2010 05:35:48 FUJITA Tomonori wrote: > > > > > > From what I have been able to tell, the IOMMU interface was written by > > > AMD/Intel to allow the kvm code to work with a common IOMMU interface. To > > > > Don't confuse the IOMMU interface with the DMA API that Arnd > > mentioned. > > > > They are not related at all. Thats not 100% true. They are not strictly related, but they are related as they may use the same backend kernel drivers to provide their functionality. Both APIs exist for different purposes, of course. > Exactly, thanks for the clarification. I also didn't realize that there > is now an include/linux/iommu.h file that only describes the PCI SR-IOV > interfaces, unlike the generic IOMMU support that we have in your > include/linux/dma-mapping.h file. The IOMMU-API is not about SR-IOV. It is about the capabilities of modern IOMMU hardware that we can not provide to the kernel with the DMA-API such as the ability to choose ourself at which io-virtual address a given cpu physical address should be mapped. Also I wouldn't call the DMA-API an IOMMU interface. The API does not depend on an IOMMU which is an important difference to the IOMMU-API. The IOMMU-API is probably not generic enough to handle all kinds of IOMMUs but its closer to a generic IOMMU-API than the DMA-API. Joerg -- Joerg Roedel - AMD Operating System Research Center Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach General Managers: Alberto Bozzo, Andrew Bowd Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632 -- 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/