On Wed, Mar 27, 2019 at 10:27:01AM +0800, Jason Wang wrote:
>
> On 2019/3/26 下午8:49, Michael S. Tsirkin wrote:
> > On Tue, Mar 26, 2019 at 02:59:19PM +0800, Jason Wang wrote:
> > > On 2019/3/25 下午8:32, Michael S. Tsirkin wrote:
> > > > On Mon, Mar 25, 2019 at 11:56:13AM +0800, Jason Wang wrote:
> > > > > We used to set backend unconditionally, this won't work for some
> > > > > guests (e.g windows driver) who may not initialize all virtqueues. For
> > > > > kernel backend, this will fail since it may try to validate the rings
> > > > > during setting backend.
> > > > >
> > > > > Fixing this by simply skipping the backend set when we find desc is
> > > > > not ready.
> > > > >
> > > > > Signed-off-by: Jason Wang<jasow...@redhat.com>
> > > > > ---
> > > > > hw/net/vhost_net.c | 15 +++++++++++++++
> > > > > 1 file changed, 15 insertions(+)
> > > > >
> > > > > diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> > > > > index be3cc88370..04fd924d15 100644
> > > > > --- a/hw/net/vhost_net.c
> > > > > +++ b/hw/net/vhost_net.c
> > > > > @@ -221,6 +221,7 @@ static int vhost_net_start_one(struct vhost_net
> > > > > *net,
> > > > > VirtIODevice *dev)
> > > > > {
> > > > > struct vhost_vring_file file = { };
> > > > > + hwaddr a;
> > > > > int r;
> > > > > net->dev.nvqs = 2;
> > > > > @@ -244,6 +245,13 @@ static int vhost_net_start_one(struct vhost_net
> > > > > *net,
> > > > > qemu_set_fd_handler(net->backend, NULL, NULL, NULL);
> > > > > file.fd = net->backend;
> > > > > for (file.index = 0; file.index < net->dev.nvqs;
> > > > > ++file.index) {
> > > > > + a = virtio_queue_get_desc_addr(dev,
> > > > > + net->dev.vq_index +
> > > > > + file.index);
> > > > > + if (a == 0) {
> > > > > + /* Queue might not be ready for start */
> > > > > + continue;
> > > > > + }
> > > > > r = vhost_net_set_backend(&net->dev, &file);
> > > > > if (r < 0) {
> > > > > r = -errno;
> > > > > @@ -256,6 +264,13 @@ fail:
> > > > > file.fd = -1;
> > > > > if (net->nc->info->type == NET_CLIENT_DRIVER_TAP) {
> > > > > while (file.index-- > 0) {
> > > > > + a = virtio_queue_get_desc_addr(dev,
> > > > > + net->dev.vq_index +
> > > > > + file.index);
> > > > > + if (a == 0) {
> > > > > + /* Queue might not be ready for start */
> > > > > + continue;
> > > > > + }
> > > > > int r = vhost_net_set_backend(&net->dev, &file);
> > > > > assert(r >= 0);
> > > > > }
> > > > I think we want an API that explicitly says "queue is enabled".
> > > > For 0.X it will return !!addr. For 1.X it will return enabled.
> > > For 1.x, desc.addr won't be set until queue_enabled is set through
> > > virtio_queue_set_vrings(). And it looks to me ccw did something similar of
> > > CMD_SET_VQ.
> > >
> > > So we're ok actually?
> > >
> > > Thanks
> > >
> > OK maybe but why can't we use an explicit API?
> > 0.X can use addr != 0 trick since there's no queue_enabled.
> >
>
> If I understand correctly, you want something similar to what V1 did? A bus
> specific queue_enable() method.
>
> Thanks
For now all I am asking for is simply:
virtio_queue_is_enabled() {
/* desc is only set when queue is enabled */
return vdev->vq[n].vring.desc != 0;
}
and then we can look at moving the enabled flag into
struct VRing longer term.
--
MST
