From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Ira W. Snyder" Subject: Re: [PATCH 2/2] vhost_net: a kernel-level virtio server Date: Wed, 12 Aug 2009 10:19:22 -0700 Message-ID: <20090812171921.GC24151@ovro.caltech.edu> References: <20090810185340.GC13924@redhat.com> <200908121903.22325.arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: virtualization@lists.linux-foundation.org, "Michael S. Tsirkin" , netdev@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Arnd Bergmann Return-path: Content-Disposition: inline In-Reply-To: <200908121903.22325.arnd@arndb.de> Sender: kvm-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Wed, Aug 12, 2009 at 07:03:22PM +0200, Arnd Bergmann wrote: > On Monday 10 August 2009, Michael S. Tsirkin wrote: > > > +struct workqueue_struct *vhost_workqueue; > > [nitpicking] This could be static. > > > +/* The virtqueue structure describes a queue attached to a device. */ > > +struct vhost_virtqueue { > > + struct vhost_dev *dev; > > + > > + /* The actual ring of buffers. */ > > + struct mutex mutex; > > + unsigned int num; > > + struct vring_desc __user *desc; > > + struct vring_avail __user *avail; > > + struct vring_used __user *used; > > + struct file *kick; > > + struct file *call; > > + struct file *error; > > + struct eventfd_ctx *call_ctx; > > + struct eventfd_ctx *error_ctx; > > + > > + struct vhost_poll poll; > > + > > + /* The routine to call when the Guest pings us, or timeout. */ > > + work_func_t handle_kick; > > + > > + /* Last available index we saw. */ > > + u16 last_avail_idx; > > + > > + /* Last index we used. */ > > + u16 last_used_idx; > > + > > + /* Outstanding buffers */ > > + unsigned int inflight; > > + > > + /* Is this blocked? */ > > + bool blocked; > > + > > + struct iovec iov[VHOST_NET_MAX_SG]; > > + > > +} ____cacheline_aligned; > > We discussed this before, and I still think this could be directly derived > from struct virtqueue, in the same way that vring_virtqueue is derived from > struct virtqueue. That would make it possible for simple device drivers > to use the same driver in both host and guest, similar to how Ira Snyder > used virtqueues to make virtio_net run between two hosts running the > same code [1]. > > Ideally, I guess you should be able to even make virtio_net work in the > host if you do that, but that could bring other complexities. I have no comments about the vhost code itself, I haven't reviewed it. It might be interesting to try using a virtio-net in the host kernel to communicate with the virtio-net running in the guest kernel. The lack of a management interface is the biggest problem you will face (setting MAC addresses, negotiating features, etc. doesn't work intuitively). Getting the network interfaces talking is relatively easy. Ira