Re: [Patch net v3] vsock/virtio: fix variables initialization during resuming

[Michael S. Tsirkin]

On Fri, Feb 14, 2025 at 09:22:00AM +0800, Junnan Wu wrote:
> When executing suspend to ram twice in a row,
> the `rx_buf_nr` and `rx_buf_max_nr` increase to three times vq->num_free.
> Then after virtqueue_get_buf and `rx_buf_nr` decreased
> in function virtio_transport_rx_work,
> the condition to fill rx buffer
> (rx_buf_nr < rx_buf_max_nr / 2) will never be met.
> 
> It is because that `rx_buf_nr` and `rx_buf_max_nr`
> are initialized only in virtio_vsock_probe(),
> but they should be reset whenever virtqueues are recreated,
> like after a suspend/resume.
> 
> Move the `rx_buf_nr` and `rx_buf_max_nr` initialization in
> virtio_vsock_vqs_init(), so we are sure that they are properly
> initialized, every time we initialize the virtqueues, either when we
> load the driver or after a suspend/resume.
> 
> To prevent erroneous atomic load operations on the `queued_replies`
> in the virtio_transport_send_pkt_work() function
> which may disrupt the scheduling of vsock->rx_work
> when transmitting reply-required socket packets,
> this atomic variable must undergo synchronized initialization
> alongside the preceding two variables after a suspend/resume.
> 
> Fixes: bd50c5dc182b ("vsock/virtio: add support for device suspend/resume")
> Link: https://lore.kernel.org/virtualization/20250207052033.2222629-1-junnan01.wu@xxxxxxxxxxx/
> Co-developed-by: Ying Gao <ying01.gao@xxxxxxxxxxx>
> Signed-off-by: Ying Gao <ying01.gao@xxxxxxxxxxx>
> Signed-off-by: Junnan Wu <junnan01.wu@xxxxxxxxxxx>


Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>

> ---
>  net/vmw_vsock/virtio_transport.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
> index b58c3818f284..f0e48e6911fc 100644
> --- a/net/vmw_vsock/virtio_transport.c
> +++ b/net/vmw_vsock/virtio_transport.c
> @@ -670,6 +670,13 @@ static int virtio_vsock_vqs_init(struct virtio_vsock *vsock)
>  	};
>  	int ret;
>  
> +	mutex_lock(&vsock->rx_lock);
> +	vsock->rx_buf_nr = 0;
> +	vsock->rx_buf_max_nr = 0;
> +	mutex_unlock(&vsock->rx_lock);
> +
> +	atomic_set(&vsock->queued_replies, 0);
> +
>  	ret = virtio_find_vqs(vdev, VSOCK_VQ_MAX, vsock->vqs, vqs_info, NULL);
>  	if (ret < 0)
>  		return ret;
> @@ -779,9 +786,6 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
>  
>  	vsock->vdev = vdev;
>  
> -	vsock->rx_buf_nr = 0;
> -	vsock->rx_buf_max_nr = 0;
> -	atomic_set(&vsock->queued_replies, 0);
>  
>  	mutex_init(&vsock->tx_lock);
>  	mutex_init(&vsock->rx_lock);
> -- 
> 2.34.1