RE: [PATCH] net/virtio: fix socket nonblocking mode affects initialization

["Xia, Chenbo" <chenbo.xia@intel.com>]

> -----Original Message-----
> From: Wang, YuanX <yuanx.wang@intel.com>
> Sent: Friday, June 17, 2022 10:42 AM
> To: maxime.coquelin@redhat.com; Xia, Chenbo <chenbo.xia@intel.com>;
> dev@dpdk.org
> Cc: Hu, Jiayu <jiayu.hu@intel.com>; He, Xingguang <xingguang.he@intel.com>;
> Wang, YuanX <yuanx.wang@intel.com>; stable@dpdk.org
> Subject: [PATCH] net/virtio: fix socket nonblocking mode affects
> initialization
> 
> The virtio-user initialization requires unix socket to receive backend
> messages in block mode. However, vhost_user_update_link_state() sets
> the same socket to nonblocking via fcntl, which affects all threads.
> Enabling the rxq interrupt can causes both of these behaviors to occur
> concurrently, with the result that the initialization may fail
> because no messages are received in nonblocking socket.
> 
> Thread 1:
> virtio_init_device()
> --> virtio_user_start_device()
> 	--> vhost_user_set_memory_table()
> 		--> vhost_user_check_reply_ack()
> 
> Thread 2:
> virtio_interrupt_handler()
> --> vhost_user_update_link_state()
> 
> Fix that by replacing O_NONBLOCK with the recv per-call option
> MSG_DONTWAIT.
> 
> Fixes: ef53b6030039 ("net/virtio-user: support LSC")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Yuan Wang <yuanx.wang@intel.com>
> ---
>  drivers/net/virtio/virtio_user/vhost_user.c | 15 +--------------
>  1 file changed, 1 insertion(+), 14 deletions(-)
> 
> diff --git a/drivers/net/virtio/virtio_user/vhost_user.c
> b/drivers/net/virtio/virtio_user/vhost_user.c
> index 7d1749114d..198bd63d3c 100644
> --- a/drivers/net/virtio/virtio_user/vhost_user.c
> +++ b/drivers/net/virtio/virtio_user/vhost_user.c
> @@ -940,15 +940,8 @@ vhost_user_update_link_state(struct virtio_user_dev
> *dev)
> 
>  	if (data->vhostfd >= 0) {
>  		int r;
> -		int flags;
> 
> -		flags = fcntl(data->vhostfd, F_GETFL);
> -		if (fcntl(data->vhostfd, F_SETFL, flags | O_NONBLOCK) == -1) {
> -			PMD_DRV_LOG(ERR, "error setting O_NONBLOCK flag");
> -			return -1;
> -		}
> -
> -		r = recv(data->vhostfd, buf, 128, MSG_PEEK);
> +		r = recv(data->vhostfd, buf, 128, MSG_PEEK | MSG_DONTWAIT);
>  		if (r == 0 || (r < 0 && errno != EAGAIN)) {
>  			dev->net_status &= (~VIRTIO_NET_S_LINK_UP);
>  			PMD_DRV_LOG(ERR, "virtio-user port %u is down", dev-
> >hw.port_id);
> @@ -963,12 +956,6 @@ vhost_user_update_link_state(struct virtio_user_dev
> *dev)
>  		} else {
>  			dev->net_status |= VIRTIO_NET_S_LINK_UP;
>  		}
> -
> -		if (fcntl(data->vhostfd, F_SETFL,
> -					flags & ~O_NONBLOCK) == -1) {
> -			PMD_DRV_LOG(ERR, "error clearing O_NONBLOCK flag");
> -			return -1;
> -		}
>  	} else if (dev->is_server) {
>  		dev->net_status &= (~VIRTIO_NET_S_LINK_UP);
>  		if (virtio_user_dev_server_reconnect(dev) >= 0)
> --
> 2.25.1

Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>