From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [Alacrityvm-devel] [PATCH v3 3/6] vbus: add a "vbus-proxy" bus model for vbus_driver objects Date: Tue, 18 Aug 2009 19:51:21 +0300 Message-ID: <4A8ADC09.3030205@redhat.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit 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 To: "Ira W. Snyder" Return-path: In-Reply-To: <20090818155329.GD31060@ovro.caltech.edu> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.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