Re: [PATCH net v2] net: stmmac: keep gso_enabled_types in sync with netdev features

[Maxime Chevallier <maxime.chevallier@bootlin.com>]

Hi Lorenzo,

On 8/12/26 06:38, Lorenzo Bianconi wrote:
> stmmac_set_gso_types() derives priv->gso_enabled_types all-or-nothing
> from NETIF_F_TSO, but stmmac_set_gso_features() advertises NETIF_F_TSO,
> NETIF_F_TSO6 and (on GMAC4) NETIF_F_GSO_UDP_L4 as independently
> toggleable features. Since netdev_fix_features() only ties TSO6 to the
> checksum features, disabling TSO (ethtool -K ethX tx-tcp-segmentation
> off) leaves TSO6 enabled in dev->features while gso_enabled_types
> becomes 0.
> 
> For a TCPv6 GSO skb the stack then keeps the frame unsegmented
> (NETIF_F_TSO6 is still set), stmmac_features_check() does not clear the
> GSO mask, and the stmmac_xmit() gate (gso_type & gso_enabled_types) is
> false, so the multi-MSS skb is transmitted through the ordinary
> descriptor path as a single oversized frame.
> 
> Derive each GSO type from its own feature bit instead, so the mask stays
> in sync with dev->features and TCPv6 (or UDP L4 on GMAC4) segmentation
> keeps working when only TSO is disabled.
> 
> Fixes: 9edfa7dab811 ("net: stmmac: enable TSO for IPv6")
> Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>

Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>

Maxime

> ---
> Changes in v2:
> - Fix possible race between stmmac_set_gso_types() and stmmac_xmit().
> - Fix fixes tag.
> - Link to v1: https://lore.kernel.org/r/20260808-stmmac-fix-tso6-features-v1-1-f82b17595052@oss.qualcomm.com
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 28 +++++++++++++----------
>  1 file changed, 16 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index a71f0df26378..df3549f55741 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -4371,16 +4371,20 @@ static void stmmac_flush_tx_descriptors(struct stmmac_priv *priv, int queue)
>  	stmmac_set_queue_tx_tail_ptr(priv, tx_q, queue, tx_q->cur_tx);
>  }
>  
> -static void stmmac_set_gso_types(struct stmmac_priv *priv, bool tso)
> +static void stmmac_set_gso_types(struct stmmac_priv *priv,
> +				 netdev_features_t features)
>  {
> -	if (!tso) {
> -		priv->gso_enabled_types = 0;
> -	} else {
> -		/* Manage oversized TCP frames for GMAC4 device */
> -		priv->gso_enabled_types = SKB_GSO_TCPV4 | SKB_GSO_TCPV6;
> -		if (priv->plat->core_type == DWMAC_CORE_GMAC4)
> -			priv->gso_enabled_types |= SKB_GSO_UDP_L4;
> -	}
> +	unsigned int gso_types = 0;
> +
> +	if (features & NETIF_F_TSO)
> +		gso_types |= SKB_GSO_TCPV4;
> +	if (features & NETIF_F_TSO6)
> +		gso_types |= SKB_GSO_TCPV6;
> +	/* Manage oversized UDP frames for GMAC4 devices */
> +	if (features & NETIF_F_GSO_UDP_L4)
> +		gso_types |= SKB_GSO_UDP_L4;
> +
> +	WRITE_ONCE(priv->gso_enabled_types, gso_types);
>  }
>  
>  static void stmmac_set_gso_features(struct net_device *ndev)
> @@ -4416,7 +4420,7 @@ static void stmmac_set_gso_features(struct net_device *ndev)
>  	if (priv->plat->core_type == DWMAC_CORE_GMAC4)
>  		ndev->hw_features |= NETIF_F_GSO_UDP_L4;
>  
> -	stmmac_set_gso_types(priv, true);
> +	stmmac_set_gso_types(priv, ndev->hw_features);
>  
>  	dev_info(priv->device, "TSO feature enabled\n");
>  }
> @@ -4766,7 +4770,7 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
>  		stmmac_stop_sw_lpi(priv);
>  
>  	if (skb_is_gso(skb) &&
> -	    skb_shinfo(skb)->gso_type & priv->gso_enabled_types)
> +	    (skb_shinfo(skb)->gso_type & READ_ONCE(priv->gso_enabled_types)))
>  		return stmmac_tso_xmit(skb, dev);
>  
>  	if (priv->est && priv->est->enable &&
> @@ -6198,7 +6202,7 @@ static int stmmac_set_features(struct net_device *netdev,
>  			stmmac_enable_sph(priv, priv->ioaddr, sph_en, chan);
>  	}
>  
> -	stmmac_set_gso_types(priv, features & NETIF_F_TSO);
> +	stmmac_set_gso_types(priv, features);
>  
>  	if (features & NETIF_F_HW_VLAN_CTAG_RX)
>  		priv->hw->hw_vlan_en = true;
> 
> ---
> base-commit: 7b53449540502cb21b32bca62a6258e22cd97bbe
> change-id: 20260808-stmmac-fix-tso6-features-7fdc5e9448e2
> 
> Best regards,