Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756663AbZFRSO6 (ORCPT ); Thu, 18 Jun 2009 14:14:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753717AbZFRSOv (ORCPT ); Thu, 18 Jun 2009 14:14:51 -0400 Received: from mga09.intel.com ([134.134.136.24]:13481 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752355AbZFRSOu convert rfc822-to-8bit (ORCPT ); Thu, 18 Jun 2009 14:14:50 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.42,246,1243839600"; d="scan'208";a="525956500" From: "Yu, Fenghua" To: "'Muli Ben-Yehuda'" CC: "'David Woodhouse'" , "'Linus Torvalds'" , "'Stephen Rothwell'" , "'Andrew Morton'" , "'Ingo Molnar'" , "'Christopher Wright'" , "Kay, Allen M" , "'lkml'" , "'iommu'" Date: Thu, 18 Jun 2009 11:14:51 -0700 Subject: RE: [PATCH 1/2] IOMMU Identity Mapping Support: iommu_identity_mapping definition Thread-Topic: [PATCH 1/2] IOMMU Identity Mapping Support: iommu_identity_mapping definition Thread-Index: AcnwQD5RhOXrHh/NTPuInTelsfnY3QAAAfgA Message-ID: References: <20090327212241.234500000@intel.com> <20090327212321.070229000@intel.com> <20090416001957.GA1527@linux-os.sc.intel.com> <1240135508.3589.75.camel@macbook.infradead.org> <20090513231351.GA22386@linux-os.sc.intel.com> <1242314271.3393.11.camel@macbook.infradead.org> <20090514175944.GA5168@linux-os.sc.intel.com> <20090618180514.GA24082@linux-os.sc.intel.com> <20090618180835.GB6838@il.ibm.com> In-Reply-To: <20090618180835.GB6838@il.ibm.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 885 Lines: 22 > >On Thu, Jun 18, 2009 at 11:05:14AM -0700, Fenghua Yu wrote: > >> IOMMU Identity Mapping Support: iommu_identity_mapping definition >> >> Identity mapping for IOMMU defines a single domain to 1:1 map all >> pci devices to all usable memory. > >Why use VT-d at all in this case? Do you have a use-case in mind? Some users want to use VT-d in KVM but are concerned of DMA remapping performance. They can use identity mapping and still have KVM on VT-d. They can also use pass through patch (sent out before) if hardware supports pass through. By default, identity mapping is turned off. "iommu=identity" can turn it on Thanks. -Fenghua -- 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/