Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755102AbZFRSo1 (ORCPT ); Thu, 18 Jun 2009 14:44:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752691AbZFRSoT (ORCPT ); Thu, 18 Jun 2009 14:44:19 -0400 Received: from mtagate5.uk.ibm.com ([195.212.29.138]:37465 "EHLO mtagate5.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751548AbZFRSoS (ORCPT ); Thu, 18 Jun 2009 14:44:18 -0400 Date: Thu, 18 Jun 2009 21:41:01 +0300 From: Muli Ben-Yehuda To: Chris Wright Cc: "Yu, Fenghua" , "'David Woodhouse'" , "'Linus Torvalds'" , "'Stephen Rothwell'" , "'Andrew Morton'" , "'Ingo Molnar'" , "Kay, Allen M" , "'lkml'" , "'iommu'" Subject: Re: [PATCH 1/2] IOMMU Identity Mapping Support: iommu_identity_mapping definition Message-ID: <20090618184101.GE6838@il.ibm.com> References: <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> <20090618182545.GC6838@il.ibm.com> <20090618183121.GB2500@x200.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090618183121.GB2500@x200.localdomain> User-Agent: Mutt/1.5.15+20070412 (2007-04-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1169 Lines: 28 On Thu, Jun 18, 2009 at 11:31:21AM -0700, Chris Wright wrote: > The 1-1 mapping is for all the host devices _not_ assigned to > guests. To eliminate the i/o overhead imposed on all guests not > using an assigned device or from i/o from host. > > It's just the same as VT-d PassThrough mode for hardware that > doesn't support it. Ok, that makes sense. Thanks, Chris. However, that doesn't appear to be what the patch does---unless I'm misreading, if iommu_identity_mapping is set, *all* devices get identity mapping. Instead of a global command line option, we need to provide a way to enable/disable pt or identity mapping (I agree that the user shouldn't know or care which is used, the kernel should pick the best one automatically) on a per BDF basis. Cheers, Muli -- Muli Ben-Yehuda | muli@il.ibm.com | +972-4-8281080 Manager, Virtualization and Systems Architecture Master Inventor, IBM Haifa Research Laboratory -- 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/