Re: [Qemu-devel] [PATCH V2 RFT] vhost_net: don't set backend for the uninitialized virtqueue

[Yuri Benditovich]

Hi Jason,

This seems ok now (4 previous patches + this one)

On Mon, Mar 25, 2019 at 5:56 AM Jason Wang <address@hidden> 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 <address@hidden>
> ---
>  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);
>          }
> --
> 2.19.1
>