Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755264AbZFRSRK (ORCPT ); Thu, 18 Jun 2009 14:17:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751968AbZFRSQ5 (ORCPT ); Thu, 18 Jun 2009 14:16:57 -0400 Received: from sous-sol.org ([216.99.217.87]:42655 "EHLO sequoia.sous-sol.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751161AbZFRSQ5 (ORCPT ); Thu, 18 Jun 2009 14:16:57 -0400 Date: Thu, 18 Jun 2009 11:13:35 -0700 From: Chris Wright To: Fenghua Yu Cc: David Woodhouse , "'Linus Torvalds'" , "'Stephen Rothwell'" , "'Andrew Morton'" , "'Ingo Molnar'" , "'Christopher Wright'" , "'Allen Kay'" , "'iommu'" , "'lkml'" Subject: Re: [PATCH 1/2] IOMMU Identity Mapping Support: iommu_identity_mapping definition Message-ID: <20090618181335.GB19771@sequoia.sous-sol.org> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090618180514.GA24082@linux-os.sc.intel.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1116 Lines: 27 * Fenghua Yu (fenghua.yu@intel.com) 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. > > This will reduces map/unmap overhead in DMA API's and improve IOMMU performance. > On 10Gb network cards, Netperf shows no performance degradation compared to > non-IOMMU performance. > > This method may lose some of DMA remapping benefits like isolation. > > The first patch defines iommu_identity_mapping varialbe which controls the > identity mapping code and is 0 by default. The only real difference between "pt" and "identity" is hardware support. We should have a single value we don't have to tell users to do different things depending on their hardware (they won't even know what they have) to achieve the same result. thanks, -chris -- 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/