From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [PATCH 3/3] virtio PCI device Date: Thu, 08 Nov 2007 09:06:19 -0600 Message-ID: <473325EB.5090907@us.ibm.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <47331F47.70304-atKUWr5tajBWk0Htik3J/w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Avi Kivity Cc: Rusty Russell , virtualization-qjLDD68F18O7TbgM5vRIOg@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: virtualization@lists.linuxfoundation.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?) > ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/