netdev - Re: [PATCH net v2] virtio_net: Fix error unwinding of XDP initialization

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Date:   Tue, 2 May 2023 14:32:48 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Feng Liu <feliu@...dia.com>
Cc:     virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
        Jason Wang <jasowang@...hat.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        Simon Horman <simon.horman@...igine.com>,
        William Tu <witu@...dia.com>, Parav Pandit <parav@...dia.com>
Subject: Re: [PATCH net v2] virtio_net: Fix error unwinding of XDP
 initialization

On Tue, May 02, 2023 at 01:41:34PM -0400, Feng Liu wrote:
> When initializing XDP in virtnet_open(), some rq xdp initialization
> may hit an error causing net device open failed. However, previous
> rqs have already initialized XDP and enabled NAPI, which is not the
> expected behavior. Need to roll back the previous rq initialization
> to avoid leaks in error unwinding of init code.
> 
> Also extract a helper function of disable queue pairs, and use newly
> introduced helper function in error unwinding and virtnet_close;
> 
> Fixes: 754b8a21a96d ("virtio_net: setup xdp_rxq_info")
> Signed-off-by: Feng Liu <feliu@...dia.com>
> Reviewed-by: William Tu <witu@...dia.com>
> Reviewed-by: Parav Pandit <parav@...dia.com>
> Reviewed-by: Simon Horman <simon.horman@...igine.com>
> Acked-by: Michael S. Tsirkin <mst@...hat.com>
> ---
>  drivers/net/virtio_net.c | 31 +++++++++++++++++++++----------
>  1 file changed, 21 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 8d8038538fc4..5cd78e154d14 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1868,6 +1868,13 @@ static int virtnet_poll(struct napi_struct *napi, int budget)
>  	return received;
>  }
>  
> +static void virtnet_disable_qp(struct virtnet_info *vi, int qp_index)
> +{
> +	virtnet_napi_tx_disable(&vi->sq[qp_index].napi);
> +	napi_disable(&vi->rq[qp_index].napi);
> +	xdp_rxq_info_unreg(&vi->rq[qp_index].xdp_rxq);
> +}
> +
>  static int virtnet_open(struct net_device *dev)
>  {
>  	struct virtnet_info *vi = netdev_priv(dev);
> @@ -1883,20 +1890,27 @@ static int virtnet_open(struct net_device *dev)
>  
>  		err = xdp_rxq_info_reg(&vi->rq[i].xdp_rxq, dev, i, vi->rq[i].napi.napi_id);
>  		if (err < 0)
> -			return err;
> +			goto err_xdp_info_reg;
>  
>  		err = xdp_rxq_info_reg_mem_model(&vi->rq[i].xdp_rxq,
>  						 MEM_TYPE_PAGE_SHARED, NULL);
> -		if (err < 0) {
> -			xdp_rxq_info_unreg(&vi->rq[i].xdp_rxq);
> -			return err;
> -		}
> +		if (err < 0)
> +			goto err_xdp_reg_mem_model;
>  
>  		virtnet_napi_enable(vi->rq[i].vq, &vi->rq[i].napi);
>  		virtnet_napi_tx_enable(vi, vi->sq[i].vq, &vi->sq[i].napi);
>  	}
>  
>  	return 0;
> +
> +	/* error unwinding of xdp init */

btw we don't really need this comment - it's how all
error handling is done anyways.
if you need to roll v3, you can drop it.

> +err_xdp_reg_mem_model:
> +	xdp_rxq_info_unreg(&vi->rq[i].xdp_rxq);
> +err_xdp_info_reg:
> +	for (i = i - 1; i >= 0; i--)
> +		virtnet_disable_qp(vi, i);
> +
> +	return err;
>  }
>  
>  static int virtnet_poll_tx(struct napi_struct *napi, int budget)
> @@ -2305,11 +2319,8 @@ static int virtnet_close(struct net_device *dev)
>  	/* Make sure refill_work doesn't re-enable napi! */
>  	cancel_delayed_work_sync(&vi->refill);
>  
> -	for (i = 0; i < vi->max_queue_pairs; i++) {
> -		virtnet_napi_tx_disable(&vi->sq[i].napi);
> -		napi_disable(&vi->rq[i].napi);
> -		xdp_rxq_info_unreg(&vi->rq[i].xdp_rxq);
> -	}
> +	for (i = 0; i < vi->max_queue_pairs; i++)
> +		virtnet_disable_qp(vi, i);
>  
>  	return 0;
>  }
> -- 
> 2.37.1 (Apple Git-137.1)