From mboxrd@z Thu Jan 1 00:00:00 1970 From: Muli Ben-Yehuda Subject: Re: VT-d support for device assignment Date: Sat, 23 Aug 2008 12:50:25 +0300 Message-ID: <20080823095025.GA6942@il.ibm.com> References: <1219389054-15332-1-git-send-email-amit.shah@qumranet.com> <48AF039B.7040805@qumranet.com> <200808231442.09332.amit.shah@qumranet.com> <48AFD97A.30309@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Amit Shah , kvm@vger.kernel.org, anthony@codemonkey.ws, jesse.barnes@intel.com, david.woodhouse@intel.com, mark.gross@intel.com, Ben-Ami Yassour1 , weidong.han@intel.com To: Avi Kivity Return-path: Received: from mtagate3.uk.ibm.com ([195.212.29.136]:41758 "EHLO mtagate3.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751828AbYHWJus (ORCPT ); Sat, 23 Aug 2008 05:50:48 -0400 Received: from d06nrmr1407.portsmouth.uk.ibm.com (d06nrmr1407.portsmouth.uk.ibm.com [9.149.38.185]) by mtagate3.uk.ibm.com (8.13.8/8.13.8) with ESMTP id m7N9olLG272398 for ; Sat, 23 Aug 2008 09:50:47 GMT Received: from d06av01.portsmouth.uk.ibm.com (d06av01.portsmouth.uk.ibm.com [9.149.37.212]) by d06nrmr1407.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v9.0) with ESMTP id m7N9olM13633242 for ; Sat, 23 Aug 2008 10:50:47 +0100 Received: from d06av01.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av01.portsmouth.uk.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m7N9okSq019214 for ; Sat, 23 Aug 2008 10:50:47 +0100 Content-Disposition: inline In-Reply-To: <48AFD97A.30309@qumranet.com> Sender: kvm-owner@vger.kernel.org List-ID: On Sat, Aug 23, 2008 at 12:33:46PM +0300, Avi Kivity wrote: > So long as there is no potential for performance or security impact, > having pvdma turned on automatically is better. We could still have > dma=noparavirt to disable it. pvdma has advantages and disadvantages. It has a significant performance impact (compared to direct map) but it also let us avoid pinning all of the guest's memory. I this this should be a guest decision whether to use it or not, so 'dma=noparavirt' to disable it seems reasonable. Cheers, Muli -- Workshop on I/O Virtualization (WIOV '08) Co-located with OSDI '08, Dec 2008, San Diego, CA http://www.usenix.org/wiov08