Re: [dpdk-dev] [PATCH] net/virtio-user: fix multiple queues fail in server mode

[Tiwei Bie <tiwei.bie@intel.com>]

On Wed, May 09, 2018 at 05:49:36PM +0800, zhiyong.yang@intel.com wrote:
> This patch fixes multiple queues failure when virtio-user works in
> server mode.
> 
> Fixes: bd8f50a45d0f ("net/virtio-user: support server mode")
> Cc: stable@dpdk.org
> Signed-off-by: Zhiyong Yang <zhiyong.yang@intel.com>
> ---
>  drivers/net/virtio/virtio_user/vhost_user.c      | 3 +++
>  drivers/net/virtio/virtio_user/virtio_user_dev.c | 9 +++++++++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/drivers/net/virtio/virtio_user/vhost_user.c b/drivers/net/virtio/virtio_user/vhost_user.c
> index a6df97a00..a9e53d7b5 100644
> --- a/drivers/net/virtio/virtio_user/vhost_user.c
> +++ b/drivers/net/virtio/virtio_user/vhost_user.c
> @@ -263,6 +263,9 @@ vhost_user_sock(struct virtio_user_dev *dev,
>  
>  	PMD_DRV_LOG(INFO, "%s", vhost_msg_strings[req]);
>  
> +	if (vhostfd < 0)
> +		return -1;

I think this is just a workaround to avoid printing
error messages in server mode.

Ideally, vhost_user_sock() shouldn't be called with
vhostfd < 0.

If we want this workaround, we should only allow
this in server mode. I.e. do the check like this:

	if (dev->is_server && vhostfd < 0)
		return -1;

> +
>  	msg.request = req;
>  	msg.flags = VHOST_USER_VERSION;
>  	msg.size = 0;
> diff --git a/drivers/net/virtio/virtio_user/virtio_user_dev.c b/drivers/net/virtio/virtio_user/virtio_user_dev.c
> index 38b8bc90d..e988dc3f4 100644
> --- a/drivers/net/virtio/virtio_user/virtio_user_dev.c
> +++ b/drivers/net/virtio/virtio_user/virtio_user_dev.c
> @@ -126,6 +126,10 @@ virtio_user_start_device(struct virtio_user_dev *dev)
>  	features &= ~(1ull << VIRTIO_NET_F_MAC);
>  	/* Strip VIRTIO_NET_F_CTRL_VQ, as devices do not really need to know */
>  	features &= ~(1ull << VIRTIO_NET_F_CTRL_VQ);
> +	/* Also disable features which depend on VIRTIO_NET_F_CTRL_VQ */
> +	features &= ~(1ull << VIRTIO_NET_F_CTRL_RX);
> +	features &= ~(1ull << VIRTIO_NET_F_CTRL_VLAN);
> +	features &= ~(1ull << VIRTIO_NET_F_CTRL_MAC_ADDR);

Is this really related to this fix?

>  	features &= ~(1ull << VIRTIO_NET_F_STATUS);
>  	ret = dev->ops->send_request(dev, VHOST_USER_SET_FEATURES, &features);
>  	if (ret < 0)
> @@ -488,6 +492,11 @@ virtio_user_handle_ctrl_msg(struct virtio_user_dev *dev, struct vring *vring,
>  		queues = *(uint16_t *)(uintptr_t)vring->desc[idx_data].addr;
>  		status = virtio_user_handle_mq(dev, queues);
>  	}
> +	/* Server mode can't enable queue pairs if vhostfd is not connected,
> +	 * we suppose that status always returns 0 in this case.
> +	 * /

As Ferruh pointed, a typo here.

> +	if (dev->is_server && dev->vhostfd < 0)
> +		status = 0;

When the connection to the backend isn't established in
server mode, what virtio_user_handle_mq() can't do is to
enable the queue pairs. But other checks in that function
are still valid. So I would suggest moving above code to
virtio_user_handle_mq().

Thanks

>  
>  	/* Update status */
>  	*(virtio_net_ctrl_ack *)(uintptr_t)vring->desc[idx_status].addr = status;
> -- 
> 2.14.3
>