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
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