From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Jackson Subject: Re: [Qemu-devel] Re: [PATCH 2 of 5] add can_dma/post_dma for direct IO Date: Mon, 22 Dec 2008 16:44:30 +0000 Message-ID: <18767.50158.909778.205969@mariner.uk.xensource.com> References: <4942B841.6010900@codemonkey.ws> <20081213143944.GD30537@random.random> <4943E6F9.1050001@codemonkey.ws> <20081213165306.GE30537@random.random> <4944251D.8080109@codemonkey.ws> <20081214164751.GF30537@random.random> <49453BF2.9070304@redhat.com> <20081214171558.GH30537@random.random> <494565A1.6030306@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: Andrea Arcangeli , chrisw@redhat.com, kvm@vger.kernel.org, Gerd Hoffmann To: qemu-devel@nongnu.org Return-path: Received: from smtp02.citrix.com ([66.165.176.63]:50203 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751440AbYLVQog (ORCPT ); Mon, 22 Dec 2008 11:44:36 -0500 In-Reply-To: <494565A1.6030306@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Avi Kivity writes ("[Qemu-devel] Re: [PATCH 2 of 5] add can_dma/post_dma for direct IO"): > Newer Xen shouldn't have this problem though; it runs qemu in kernel > mode in a dedicated 64-bit domain. This is not yet the default configuration and there are still various reasons why you might not want to use it. I expect we'll retain the dom0 user process option for a while yet. I think there is continued value in being able to emulate a guest whose physical address space exceeds the virtual address space in the host. The whole assumption that all guest accessible RAM is mapped at once, contiguously, is I think wrong. Ian. From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1LEntX-0001BA-OV for qemu-devel@nongnu.org; Mon, 22 Dec 2008 11:44:39 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1LEntW-0001Ao-0Z for qemu-devel@nongnu.org; Mon, 22 Dec 2008 11:44:39 -0500 Received: from [199.232.76.173] (port=44842 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LEntV-0001Al-UA for qemu-devel@nongnu.org; Mon, 22 Dec 2008 11:44:37 -0500 Received: from smtp02.citrix.com ([66.165.176.63]:48140) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1LEntV-0007tk-JO for qemu-devel@nongnu.org; Mon, 22 Dec 2008 11:44:37 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <18767.50158.909778.205969@mariner.uk.xensource.com> Date: Mon, 22 Dec 2008 16:44:30 +0000 Subject: Re: [Qemu-devel] Re: [PATCH 2 of 5] add can_dma/post_dma for direct IO In-Reply-To: <494565A1.6030306@redhat.com> References: <4942B841.6010900@codemonkey.ws> <20081213143944.GD30537@random.random> <4943E6F9.1050001@codemonkey.ws> <20081213165306.GE30537@random.random> <4944251D.8080109@codemonkey.ws> <20081214164751.GF30537@random.random> <49453BF2.9070304@redhat.com> <20081214171558.GH30537@random.random> <494565A1.6030306@redhat.com> From: Ian Jackson Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Andrea Arcangeli , chrisw@redhat.com, Gerd Hoffmann , kvm@vger.kernel.org Avi Kivity writes ("[Qemu-devel] Re: [PATCH 2 of 5] add can_dma/post_dma for direct IO"): > Newer Xen shouldn't have this problem though; it runs qemu in kernel > mode in a dedicated 64-bit domain. This is not yet the default configuration and there are still various reasons why you might not want to use it. I expect we'll retain the dom0 user process option for a while yet. I think there is continued value in being able to emulate a guest whose physical address space exceeds the virtual address space in the host. The whole assumption that all guest accessible RAM is mapped at once, contiguously, is I think wrong. Ian.