Re: [PATCH 14/16] virtio-net: support queue_enable for vhost-user

[Jason Wang <jasowang@redhat.com>]

在 2022/7/18 19:17, Kangjie Xu 写道:
> Support queue enable in vhost-user scenario. It will be called when
> a vq reset operation is performed and the vq will be restared.
>
> It should be noted that we can restart the vq when the vhost has
> already started. When launching a new vhost-user device, the vhost
> is not started and all vqs are not initalized until
> VIRTIO_PCI_COMMON_STATUS is written. Thus, we should use vhost_started
> to differentiate the two cases: vq reset and device start.
>
> Signed-off-by: Kangjie Xu <kangjie.xu@linux.alibaba.com>
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> ---
>   hw/net/virtio-net.c | 20 ++++++++++++++++++++
>   1 file changed, 20 insertions(+)
>
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index 8396e21a67..2c26e2ef73 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -544,6 +544,25 @@ static void virtio_net_queue_reset(VirtIODevice *vdev, uint32_t queue_index)
>       assert(!virtio_net_get_subqueue(nc)->async_tx.elem);
>   }
>   
> +static void virtio_net_queue_enable(VirtIODevice *vdev, uint32_t queue_index)
> +{
> +    VirtIONet *n = VIRTIO_NET(vdev);
> +    NetClientState *nc = qemu_get_subqueue(n->nic, vq2q(queue_index));
> +    int r;
> +
> +    if (!nc->peer || !vdev->vhost_started) {
> +        return;
> +    }
> +
> +    if (nc->peer->info->type == NET_CLIENT_DRIVER_VHOST_USER) {
> +        r = vhost_virtqueue_restart(vdev, nc, queue_index);
> +        if (r < 0) {
> +            error_report("unable to restart vhost net virtqueue: %d, "
> +                            "when resetting the queue", queue_index);
> +        }
> +    }
> +}


So we don't check queue_enable in vhost_dev_start(), does this mean the 
queue_enable is actually meaningless (since the virtqueue is already 
started there)?

And another issue is

peet_attach/peer_detach() "abuse" vhost_set_vring_enable(). This 
probably means we need to invent new type of request instead of re-using 
VHOST_USER_SET_VRING_ENABLE.

Thanks


> +
>   static void virtio_net_reset(VirtIODevice *vdev)
>   {
>       VirtIONet *n = VIRTIO_NET(vdev);
> @@ -3781,6 +3800,7 @@ static void virtio_net_class_init(ObjectClass *klass, void *data)
>       vdc->bad_features = virtio_net_bad_features;
>       vdc->reset = virtio_net_reset;
>       vdc->queue_reset = virtio_net_queue_reset;
> +    vdc->queue_enable = virtio_net_queue_enable;
>       vdc->set_status = virtio_net_set_status;
>       vdc->guest_notifier_mask = virtio_net_guest_notifier_mask;
>       vdc->guest_notifier_pending = virtio_net_guest_notifier_pending;