From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759414AbZHRQvr (ORCPT ); Tue, 18 Aug 2009 12:51:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759400AbZHRQvq (ORCPT ); Tue, 18 Aug 2009 12:51:46 -0400 Received: from mx2.redhat.com ([66.187.237.31]:40503 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759390AbZHRQvp (ORCPT ); Tue, 18 Aug 2009 12:51:45 -0400 Message-ID: <4A8ADC09.3030205@redhat.com> Date: Tue, 18 Aug 2009 19:51:21 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.1) Gecko/20090814 Fedora/3.0-2.6.b3.fc11 Thunderbird/3.0b3 MIME-Version: 1.0 To: "Ira W. Snyder" CC: "Michael S. Tsirkin" , Gregory Haskins , kvm@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, alacrityvm-devel@lists.sourceforge.net, Anthony Liguori , Ingo Molnar , Gregory Haskins Subject: Re: [Alacrityvm-devel] [PATCH v3 3/6] vbus: add a "vbus-proxy" bus model for vbus_driver objects References: <20090814154125.26116.70709.stgit@dev.haskins.net> <20090814154308.26116.46980.stgit@dev.haskins.net> <20090815103243.GA26749@elte.hu> <4A870964.9090408@codemonkey.ws> <4A8965E0.8050608@gmail.com> <20090817174142.GA11140@redhat.com> <4A89BAC5.9040400@gmail.com> <20090818084606.GA13878@redhat.com> <20090818155329.GD31060@ovro.caltech.edu> In-Reply-To: <20090818155329.GD31060@ovro.caltech.edu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/18/2009 06:53 PM, Ira W. Snyder wrote: > So, in my system, copy_(to|from)_user() is completely wrong. There is no > userspace, only a physical system. In fact, because normal x86 computers > do not have DMA controllers, the host system doesn't actually handle any > data transfer! > In fact, modern x86s do have dma engines these days (google for Intel I/OAT), and one of our plans for vhost-net is to allow their use for packets above a certain size. So a patch allowing vhost-net to optionally use a dma engine is a good thing. > I used virtio-net in both the guest and host systems in my example > virtio-over-PCI patch, and succeeded in getting them to communicate. > However, the lack of any setup interface means that the devices must be > hardcoded into both drivers, when the decision could be up to userspace. > I think this is a problem that vbus could solve. > Exposing a knob to userspace is not an insurmountable problem; vhost-net already allows changing the memory layout, for example. -- error compiling committee.c: too many arguments to function