From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761366AbXKHPGU (ORCPT ); Thu, 8 Nov 2007 10:06:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759031AbXKHPGJ (ORCPT ); Thu, 8 Nov 2007 10:06:09 -0500 Received: from e31.co.us.ibm.com ([32.97.110.149]:40399 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757920AbXKHPGH (ORCPT ); Thu, 8 Nov 2007 10:06:07 -0500 Message-ID: <473325EB.5090907@us.ibm.com> Date: Thu, 08 Nov 2007 09:06:19 -0600 From: Anthony Liguori User-Agent: Thunderbird 2.0.0.6 (X11/20071022) MIME-Version: 1.0 To: Avi Kivity CC: linux-kernel@vger.kernel.org, Rusty Russell , virtualization@lists.osdl.org, kvm-devel@lists.sourceforge.net Subject: Re: [kvm-devel] [PATCH 3/3] virtio PCI device References: <11944899922822-git-send-email-aliguori@us.ibm.com> <11944900141678-git-send-email-aliguori@us.ibm.com> <11944900152750-git-send-email-aliguori@us.ibm.com> <11944900163817-git-send-email-aliguori@us.ibm.com> <4732A8E5.6090307@qumranet.com> <47331531.8070709@us.ibm.com> <47331F47.70304@qumranet.com> In-Reply-To: <47331F47.70304@qumranet.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Avi Kivity wrote: > If a pci device is capable of dma (or issuing interrupts), it will be > useless with pv pci. Hrm, I think we may be talking about different things. Are you thinking that the driver I posted allows you to do PCI pass-through over virtio? That's not what it is. The driver I posted is a virtio implementation that uses a PCI device. This lets you use virtio-blk and virtio-net under KVM. The alternative to this virtio PCI device would be a virtio transport built with hypercalls like lguest has. I choose a PCI device because it ensured that each virtio device showed up like a normal PCI device. Am I misunderstanding what you're asking about? Regards, Anthony Liguori > >>> I think that with Amit's pvdma patches you >>> can support dma-capable devices as well without too much fuss. >>> >> >> What is the use case you're thinking of? A semi-paravirt driver that >> does dma directly to a device? > > No, an unmodified driver that, by using clever tricks with dma_ops, > can do dma directly to guest memory. See Amit's patches. > > In fact, why do a virtio transport at all? It can be done either with > trap'n'emulate, or by directly mapping the device mmio space into the > guest. > > > (what use case are you considering? devices without interrupts and > dma? pci door stoppers?) >