netdev - Re: [PATCH net-next 2/3] virtio_net: Hold RTNL for NAPI to queue mapping

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Message-ID: <253f7ca1-758a-40f1-aeda-411a6a68e31d@engleder-embedded.com>
Date: Fri, 10 Jan 2025 23:22:14 +0100
From: Gerhard Engleder <gerhard@...leder-embedded.com>
To: Joe Damato <jdamato@...tly.com>, netdev@...r.kernel.org
Cc: mkarsten@...terloo.ca, "Michael S. Tsirkin" <mst@...hat.com>,
 Jason Wang <jasowang@...hat.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
 Eugenio Pérez <eperezma@...hat.com>,
 Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 "open list:VIRTIO CORE AND NET DRIVERS" <virtualization@...ts.linux.dev>,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 2/3] virtio_net: Hold RTNL for NAPI to queue
 mapping


On 10.01.25 21:26, Joe Damato wrote:
> Prepare for NAPI to queue mapping by holding RTNL in code paths where
> NAPIs will be mapped to queue IDs and RTNL is not currently held.
> 
> Signed-off-by: Joe Damato <jdamato@...tly.com>
> ---
>   drivers/net/virtio_net.c | 17 ++++++++++++++---
>   1 file changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index cff18c66b54a..4e88d352d3eb 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -2803,11 +2803,17 @@ static void virtnet_napi_do_enable(struct virtqueue *vq,
>   	local_bh_enable();
>   }
>   
> -static void virtnet_napi_enable(struct virtqueue *vq, struct napi_struct *napi)
> +static void virtnet_napi_enable_lock(struct virtqueue *vq,
> +				     struct napi_struct *napi)
>   {
>   	virtnet_napi_do_enable(vq, napi);
>   }
>   
> +static void virtnet_napi_enable(struct virtqueue *vq, struct napi_struct *napi)
> +{
> +	virtnet_napi_enable_lock(vq, napi);
> +}
> +
>   static void virtnet_napi_tx_enable(struct virtnet_info *vi,
>   				   struct virtqueue *vq,
>   				   struct napi_struct *napi)
> @@ -2844,7 +2850,7 @@ static void refill_work(struct work_struct *work)
>   
>   		napi_disable(&rq->napi);
>   		still_empty = !try_fill_recv(vi, rq, GFP_KERNEL);
> -		virtnet_napi_enable(rq->vq, &rq->napi);
> +		virtnet_napi_enable_lock(rq->vq, &rq->napi);
>   
>   		/* In theory, this can happen: if we don't get any buffers in
>   		 * we will *never* try to fill again.
> @@ -5621,8 +5627,11 @@ static void virtnet_freeze_down(struct virtio_device *vdev)
>   	netif_tx_lock_bh(vi->dev);
>   	netif_device_detach(vi->dev);
>   	netif_tx_unlock_bh(vi->dev);
> -	if (netif_running(vi->dev))
> +	if (netif_running(vi->dev)) {
> +		rtnl_lock();
>   		virtnet_close(vi->dev);
> +		rtnl_unlock();
> +	}
>   }
>   
>   static int init_vqs(struct virtnet_info *vi);
> @@ -5642,7 +5651,9 @@ static int virtnet_restore_up(struct virtio_device *vdev)
>   	enable_rx_mode_work(vi);
>   
>   	if (netif_running(vi->dev)) {
> +		rtnl_lock();
>   		err = virtnet_open(vi->dev);
> +		rtnl_unlock();
>   		if (err)
>   			return err;
>   	}

Reviewed-by: Gerhard Engleder <gerhard@...leder-embedded.com>