netdev - Re: [PATCH net] net: socionext: netsec: always grab descriptor lock

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Date:   Tue, 1 Oct 2019 11:37:07 +0300
From:   Ilias Apalodimas <ilias.apalodimas@...aro.org>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        lorenzo.bianconi@...hat.com
Subject: Re: [PATCH net] net: socionext: netsec: always grab descriptor lock

On Tue, Oct 01, 2019 at 10:33:51AM +0200, Lorenzo Bianconi wrote:
> Always acquire tx descriptor spinlock even if a xdp program is not loaded
> on the netsec device since ndo_xdp_xmit can run concurrently with
> netsec_netdev_start_xmit and netsec_clean_tx_dring. This can happen
> loading a xdp program on a different device (e.g virtio-net) and
> xdp_do_redirect_map/xdp_do_redirect_slow can redirect to netsec even if
> we do not have a xdp program on it.
> 
> Fixes: ba2b232108d3 ("net: netsec: add XDP support")
> Tested-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> ---
>  drivers/net/ethernet/socionext/netsec.c | 30 ++++++-------------------
>  1 file changed, 7 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/net/ethernet/socionext/netsec.c b/drivers/net/ethernet/socionext/netsec.c
> index 55db7fbd43cc..f9e6744d8fd6 100644
> --- a/drivers/net/ethernet/socionext/netsec.c
> +++ b/drivers/net/ethernet/socionext/netsec.c
> @@ -282,7 +282,6 @@ struct netsec_desc_ring {
>  	void *vaddr;
>  	u16 head, tail;
>  	u16 xdp_xmit; /* netsec_xdp_xmit packets */
> -	bool is_xdp;
>  	struct page_pool *page_pool;
>  	struct xdp_rxq_info xdp_rxq;
>  	spinlock_t lock; /* XDP tx queue locking */
> @@ -634,8 +633,7 @@ static bool netsec_clean_tx_dring(struct netsec_priv *priv)
>  	unsigned int bytes;
>  	int cnt = 0;
>  
> -	if (dring->is_xdp)
> -		spin_lock(&dring->lock);
> +	spin_lock(&dring->lock);
>  
>  	bytes = 0;
>  	entry = dring->vaddr + DESC_SZ * tail;
> @@ -682,8 +680,8 @@ static bool netsec_clean_tx_dring(struct netsec_priv *priv)
>  		entry = dring->vaddr + DESC_SZ * tail;
>  		cnt++;
>  	}
> -	if (dring->is_xdp)
> -		spin_unlock(&dring->lock);
> +
> +	spin_unlock(&dring->lock);
>  
>  	if (!cnt)
>  		return false;
> @@ -799,9 +797,6 @@ static void netsec_set_tx_de(struct netsec_priv *priv,
>  	de->data_buf_addr_lw = lower_32_bits(desc->dma_addr);
>  	de->buf_len_info = (tx_ctrl->tcp_seg_len << 16) | desc->len;
>  	de->attr = attr;
> -	/* under spin_lock if using XDP */
> -	if (!dring->is_xdp)
> -		dma_wmb();
>  
>  	dring->desc[idx] = *desc;
>  	if (desc->buf_type == TYPE_NETSEC_SKB)
> @@ -1123,12 +1118,10 @@ static netdev_tx_t netsec_netdev_start_xmit(struct sk_buff *skb,
>  	u16 tso_seg_len = 0;
>  	int filled;
>  
> -	if (dring->is_xdp)
> -		spin_lock_bh(&dring->lock);
> +	spin_lock_bh(&dring->lock);
>  	filled = netsec_desc_used(dring);
>  	if (netsec_check_stop_tx(priv, filled)) {
> -		if (dring->is_xdp)
> -			spin_unlock_bh(&dring->lock);
> +		spin_unlock_bh(&dring->lock);
>  		net_warn_ratelimited("%s %s Tx queue full\n",
>  				     dev_name(priv->dev), ndev->name);
>  		return NETDEV_TX_BUSY;
> @@ -1161,8 +1154,7 @@ static netdev_tx_t netsec_netdev_start_xmit(struct sk_buff *skb,
>  	tx_desc.dma_addr = dma_map_single(priv->dev, skb->data,
>  					  skb_headlen(skb), DMA_TO_DEVICE);
>  	if (dma_mapping_error(priv->dev, tx_desc.dma_addr)) {
> -		if (dring->is_xdp)
> -			spin_unlock_bh(&dring->lock);
> +		spin_unlock_bh(&dring->lock);
>  		netif_err(priv, drv, priv->ndev,
>  			  "%s: DMA mapping failed\n", __func__);
>  		ndev->stats.tx_dropped++;
> @@ -1177,8 +1169,7 @@ static netdev_tx_t netsec_netdev_start_xmit(struct sk_buff *skb,
>  	netdev_sent_queue(priv->ndev, skb->len);
>  
>  	netsec_set_tx_de(priv, dring, &tx_ctrl, &tx_desc, skb);
> -	if (dring->is_xdp)
> -		spin_unlock_bh(&dring->lock);
> +	spin_unlock_bh(&dring->lock);
>  	netsec_write(priv, NETSEC_REG_NRM_TX_PKTCNT, 1); /* submit another tx */
>  
>  	return NETDEV_TX_OK;
> @@ -1262,7 +1253,6 @@ static int netsec_alloc_dring(struct netsec_priv *priv, enum ring_id id)
>  static void netsec_setup_tx_dring(struct netsec_priv *priv)
>  {
>  	struct netsec_desc_ring *dring = &priv->desc_ring[NETSEC_RING_TX];
> -	struct bpf_prog *xdp_prog = READ_ONCE(priv->xdp_prog);
>  	int i;
>  
>  	for (i = 0; i < DESC_NUM; i++) {
> @@ -1275,12 +1265,6 @@ static void netsec_setup_tx_dring(struct netsec_priv *priv)
>  		 */
>  		de->attr = 1U << NETSEC_TX_SHIFT_OWN_FIELD;
>  	}
> -
> -	if (xdp_prog)
> -		dring->is_xdp = true;
> -	else
> -		dring->is_xdp = false;
> -
>  }
>  
>  static int netsec_setup_rx_dring(struct netsec_priv *priv)
> -- 
> 2.21.0
> 

Reviewed-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>