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

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Message-ID: <20250214071714-mutt-send-email-mst@kernel.org>
Date: Fri, 14 Feb 2025 07:17:22 -0500
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Junnan Wu <junnan01.wu@...sung.com>
Cc: sgarzare@...hat.com, davem@...emloft.net, edumazet@...gle.com,
	eperezma@...hat.com, horms@...nel.org, jasowang@...hat.com,
	kuba@...nel.org, kvm@...r.kernel.org, lei19.wang@...sung.com,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	pabeni@...hat.com, q1.huang@...sung.com, stefanha@...hat.com,
	virtualization@...ts.linux.dev, xuanzhuo@...ux.alibaba.com,
	ying01.gao@...sung.com, ying123.xu@...sung.com
Subject: Re: [Patch net v3] vsock/virtio: fix variables initialization during
 resuming

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@samsung.com/
> Co-developed-by: Ying Gao <ying01.gao@...sung.com>
> Signed-off-by: Ying Gao <ying01.gao@...sung.com>
> Signed-off-by: Junnan Wu <junnan01.wu@...sung.com>


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

> ---
>  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