Subject: Re: [PATCH net-next v3 05/15] net: Proxy net_mp_{open,close}_rxq for mapped queues

From: Stanislav Fomichev <[email-masked]>
Date: Fri, 24 Oct 2025 11:36:49 -0700

On 10/20, Daniel Borkmann wrote:
> From: David Wei <[email-masked]>
> 
> When a process in a container wants to setup a memory provider, it will
> use the virtual netdev and a mapped rxq, and call net_mp_{open,close}_rxq
> to try and restart the queue. At this point, proxy the queue restart on
> the real rxq in the physical netdev.
> 
> For memory providers (io_uring zero-copy rx and devmem), it causes the
> real rxq in the physical netdev to be filled from a memory provider that
> has DMA mapped memory from a process within a container.
> 
> Signed-off-by: David Wei <[email-masked]>
> Co-developed-by: Daniel Borkmann <[email-masked]>
> Signed-off-by: Daniel Borkmann <[email-masked]>
> ---
>  include/net/page_pool/memory_provider.h |  4 +-
>  net/core/netdev_rx_queue.c              | 57 +++++++++++++++++--------
>  2 files changed, 41 insertions(+), 20 deletions(-)
> 
> diff --git a/include/net/page_pool/memory_provider.h b/include/net/page_pool/memory_provider.h
> index ada4f968960a..b6f811c3416b 100644
> --- a/include/net/page_pool/memory_provider.h
> +++ b/include/net/page_pool/memory_provider.h
> @@ -23,12 +23,12 @@ bool net_mp_niov_set_dma_addr(struct net_iov *niov, dma_addr_t addr);
>  void net_mp_niov_set_page_pool(struct page_pool *pool, struct net_iov *niov);
>  void net_mp_niov_clear_page_pool(struct net_iov *niov);
>  
> -int net_mp_open_rxq(struct net_device *dev, unsigned ifq_idx,
> +int net_mp_open_rxq(struct net_device *dev, unsigned int rxq_idx,
>  		    struct pp_memory_provider_params *p);
>  int __net_mp_open_rxq(struct net_device *dev, unsigned int rxq_idx,
>  		      const struct pp_memory_provider_params *p,
>  		      struct netlink_ext_ack *extack);
> -void net_mp_close_rxq(struct net_device *dev, unsigned ifq_idx,
> +void net_mp_close_rxq(struct net_device *dev, unsigned int rxq_idx,
>  		      struct pp_memory_provider_params *old_p);
>  void __net_mp_close_rxq(struct net_device *dev, unsigned int rxq_idx,
>  			const struct pp_memory_provider_params *old_p);
> diff --git a/net/core/netdev_rx_queue.c b/net/core/netdev_rx_queue.c
> index 8ee289316c06..b4ff3497e086 100644
> --- a/net/core/netdev_rx_queue.c
> +++ b/net/core/netdev_rx_queue.c
> @@ -170,48 +170,63 @@ int __net_mp_open_rxq(struct net_device *dev, unsigned int rxq_idx,
>  		      struct netlink_ext_ack *extack)
>  {
>  	struct netdev_rx_queue *rxq;
> +	bool needs_unlock = false;
>  	int ret;
>  
>  	if (!netdev_need_ops_lock(dev))
>  		return -EOPNOTSUPP;
> -
>  	if (rxq_idx >= dev->real_num_rx_queues) {
>  		NL_SET_ERR_MSG(extack, "rx queue index out of range");
>  		return -ERANGE;
>  	}
> -	rxq_idx = array_index_nospec(rxq_idx, dev->real_num_rx_queues);
>  
> +	rxq_idx = array_index_nospec(rxq_idx, dev->real_num_rx_queues);
> +	rxq = netif_get_rx_queue_peer_locked(&dev, &rxq_idx, &needs_unlock);
> +	if (!rxq) {
> +		NL_SET_ERR_MSG(extack, "rx queue peered to a virtual netdev");
> +		return -EBUSY;
> +	}
> +	if (!dev->dev.parent) {
> +		NL_SET_ERR_MSG(extack, "rx queue is mapped to a virtual netdev");
> +		ret = -EBUSY;
> +		goto out;
> +	}
>  	if (dev->cfg->hds_config != ETHTOOL_TCP_DATA_SPLIT_ENABLED) {
>  		NL_SET_ERR_MSG(extack, "tcp-data-split is disabled");
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		goto out;
>  	}
>  	if (dev->cfg->hds_thresh) {
>  		NL_SET_ERR_MSG(extack, "hds-thresh is not zero");
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		goto out;
>  	}
>  	if (dev_xdp_prog_count(dev)) {
>  		NL_SET_ERR_MSG(extack, "unable to custom memory provider to device with XDP program attached");
> -		return -EEXIST;
> +		ret = -EEXIST;
> +		goto out;
>  	}
> -
> -	rxq = __netif_get_rx_queue(dev, rxq_idx);
>  	if (rxq->mp_params.mp_ops) {
>  		NL_SET_ERR_MSG(extack, "designated queue already memory provider bound");
> -		return -EEXIST;
> +		ret = -EEXIST;
> +		goto out;
>  	}
>  #ifdef CONFIG_XDP_SOCKETS
>  	if (rxq->pool) {
>  		NL_SET_ERR_MSG(extack, "designated queue already in use by AF_XDP");
> -		return -EBUSY;
> +		ret = -EBUSY;
> +		goto out;
>  	}
>  #endif
> -
>  	rxq->mp_params = *p;
>  	ret = netdev_rx_queue_restart(dev, rxq_idx);
>  	if (ret) {
>  		rxq->mp_params.mp_ops = NULL;
>  		rxq->mp_params.mp_priv = NULL;
>  	}
> +out:
> +	if (needs_unlock)
> +		netdev_unlock(dev);

Can we do something better than needs_unlock flag? Maybe something like the
following?

netif_put_rx_queue_peer_locked(orig_dev, dev)
{
	if (orig_dev != dev)
		netdev_unlock(dev);
}

Then we can do:

orig_dev = dev;
rxq = netif_get_rx_queue_peer_locked(&dev, &rx_idx);
...
netif_put_rx_queue_peer_locked(orig_dev, dev);