On Tue, Aug 25, 2020 at 03:41:10PM +0200, Guennadi Liakhovetski wrote: > Hi Michael, > > ...back from holidays and still unsure what your preferred solution > for the message layout would be: > > On Wed, Aug 12, 2020 at 02:32:43PM +0200, Guennadi Liakhovetski wrote: > > Hi Michael, > > > > Thanks for a review. > > > > On Mon, Aug 10, 2020 at 09:44:15AM -0400, Michael S. Tsirkin wrote: > > > On Tue, Aug 04, 2020 at 05:19:17PM +0200, Guennadi Liakhovetski wrote: > > [snip] > > > > > > > +static int vhost_rpmsg_get_single(struct vhost_virtqueue *vq) > > > > > > +{ > > > > > > + struct vhost_rpmsg *vr = container_of(vq->dev, struct vhost_rpmsg, dev); > > > > > > + unsigned int out, in; > > > > > > + int head = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov), &out, &in, > > > > > > + NULL, NULL); > > > > > > + if (head < 0) { > > > > > > + vq_err(vq, "%s(): error %d getting buffer\n", > > > > > > + __func__, head); > > > > > > + return head; > > > > > > + } > > > > > > + > > > > > > + /* Nothing new? */ > > > > > > + if (head == vq->num) > > > > > > + return head; > > > > > > + > > > > > > + if (vq == &vr->vq[VIRTIO_RPMSG_RESPONSE] && (out || in != 1)) { > > > > > > > > > > This in != 1 looks like a dependency on a specific message layout. > > > > > virtio spec says to avoid these. Using iov iters it's not too hard to do > > > > > ... > > > > > > > > This is an RPMsg VirtIO implementation, and it has to match the virtio_rpmsg_bus.c > > > > driver, and that one has specific VirtIO queue and message usage patterns. > > > > > > That could be fine for legacy virtio, but now you are claiming support > > > for virtio 1, so need to fix these assumptions in the device. > > > > I can just deop these checks without changing anything else, that still would work. > > I could also make this work with "any" layout - either ignoring any left-over > > buffers or maybe even getting them one by one. But I wouldn't even be able to test > > those modes without modifying / breaking the current virtio-rpmsg driver. What's > > the preferred solution? > > Could you elaborate a bit please? > > Thanks > Guennadi I'd prefer it that we make it work with any layout. For testing, there was a hack for virtio ring which split up descriptors at a random boundary. I'll try to locate it and post, sounds like something we might want upstream for debugging. -- MST