Re: [PATCH v5 11/15] vhost-net: vhost-kernel: introduce vhost_net_virtqueue_restart()

[Jason Wang]

On Wed, Sep 14, 2022 at 12:21 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
>
> From: Kangjie Xu <kangjie.xu@linux.alibaba.com>
>
> Introduce vhost_net_virtqueue_restart(), which can restart the
> specific virtqueue when the vhost net started running before.
> If it fails to restart the virtqueue, the device will be stopped.
>
> Here we do not reuse vhost_net_start_one() or vhost_dev_start()
> because they work at queue pair level. The mem table and features
> do not change, so we can call the vhost_virtqueue_start() to
> restart a specific queue.
>
> This patch only considers the case of vhost-kernel, when
> NetClientDriver is NET_CLIENT_DRIVER_TAP.
>
> Signed-off-by: Kangjie Xu <kangjie.xu@linux.alibaba.com>
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>

Acked-by: Jason Wang <jasowang@redhat.com>

> ---
>  hw/net/vhost_net.c      | 53 +++++++++++++++++++++++++++++++++++++++++
>  include/net/vhost_net.h |  2 ++
>  2 files changed, 55 insertions(+)
>
> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index 8beecb4d22..d2926e2ed6 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -34,6 +34,7 @@
>  #include "standard-headers/linux/virtio_ring.h"
>  #include "hw/virtio/vhost.h"
>  #include "hw/virtio/virtio-bus.h"
> +#include "linux-headers/linux/vhost.h"
>
>
>  /* Features supported by host kernel. */
> @@ -556,3 +557,55 @@ void vhost_net_virtqueue_reset(VirtIODevice *vdev, 
> NetClientState *nc,
>                           net->dev.vqs + idx,
>                           net->dev.vq_index + idx);
>  }
> +
> +int vhost_net_virtqueue_restart(VirtIODevice *vdev, NetClientState *nc,
> +                                int vq_index)
> +{
> +    VHostNetState *net = get_vhost_net(nc->peer);
> +    const VhostOps *vhost_ops = net->dev.vhost_ops;
> +    struct vhost_vring_file file = { };
> +    int idx, r;
> +
> +    if (!net->dev.started) {
> +        return -EBUSY;
> +    }
> +
> +    /* should only be called after backend is connected */
> +    assert(vhost_ops);
> +
> +    idx = vhost_ops->vhost_get_vq_index(&net->dev, vq_index);
> +
> +    r = vhost_virtqueue_start(&net->dev,
> +                              vdev,
> +                              net->dev.vqs + idx,
> +                              net->dev.vq_index + idx);
> +    if (r < 0) {
> +        goto err_start;
> +    }
> +
> +    if (net->nc->info->type == NET_CLIENT_DRIVER_TAP) {
> +        file.index = idx;
> +        file.fd = net->backend;
> +        r = vhost_net_set_backend(&net->dev, &file);
> +        if (r < 0) {
> +            r = -errno;
> +            goto err_start;
> +        }
> +    }
> +
> +    return 0;
> +
> +err_start:
> +    error_report("Error when restarting the queue.");
> +
> +    if (net->nc->info->type == NET_CLIENT_DRIVER_TAP) {
> +        file.fd = VHOST_FILE_UNBIND;
> +        file.index = idx;
> +        int r = vhost_net_set_backend(&net->dev, &file);
> +        assert(r >= 0);
> +    }
> +
> +    vhost_dev_stop(&net->dev, vdev);
> +
> +    return r;
> +}
> diff --git a/include/net/vhost_net.h b/include/net/vhost_net.h
> index 85d85a4957..40b9a40074 100644
> --- a/include/net/vhost_net.h
> +++ b/include/net/vhost_net.h
> @@ -50,4 +50,6 @@ int vhost_net_set_mtu(struct vhost_net *net, uint16_t mtu);
>
>  void vhost_net_virtqueue_reset(VirtIODevice *vdev, NetClientState *nc,
>                                 int vq_index);
> +int vhost_net_virtqueue_restart(VirtIODevice *vdev, NetClientState *nc,
> +                                int vq_index);
>  #endif
> --
> 2.32.0.3.g01195cf9f
>