Re: [PATCH net-next v4 1/6] net: xilinx: axienet: Introduce axienet_config for MAC-specific ops

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] net: axienet: jumbo capability flag is ignored in MTU configuration
--

commit 865179930c894853c80ee8475041f18d377414d1
Author: Suraj Gupta <suraj.gupta2@amd.com>

    net: xilinx: axienet: Introduce axienet_config for MAC-specific ops
    
    Introduce an axienet_config structure to abstract MAC-type-specific
    operations, preparing the driver for supporting additional MAC types
    beyond the existing 1G Ethernet.

> diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> index ae8ed4495ea0e..5af48d5cbed3b 100644
> --- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> +++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
[ ... ]
> @@ -711,19 +744,23 @@ static void axienet_dma_stop(struct axienet_local *lp)
>   */
>  static int axienet_device_reset(struct net_device *ndev)
>  {
> -	u32 axienet_status;
>  	struct axienet_local *lp = netdev_priv(ndev);
>  	int ret;
>  
> +	if (lp->axienet_config->gt_reset)
> +		lp->axienet_config->gt_reset(lp);
> +
>  	lp->max_frm_size = XAE_MAX_VLAN_FRAME_SIZE;
> -	lp->options |= XAE_OPTION_VLAN;
> +
> +	if (lp->axienet_config->vlan)
> +		lp->options |= XAE_OPTION_VLAN;
>  	lp->options &= (~XAE_OPTION_JUMBO);
>  
>  	if (ndev->mtu > XAE_MTU && ndev->mtu <= XAE_JUMBO_MTU) {
>  		lp->max_frm_size = ndev->mtu + VLAN_ETH_HLEN +
>  					XAE_TRL_SIZE;
>  
> -		if (lp->max_frm_size <= lp->rxmem)
> +		if (lp->max_frm_size <= lp->rxmem && lp->axienet_config->jumbo)
>  			lp->options |= XAE_OPTION_JUMBO;
>  	}

[Severity: Medium]
Does this code silently drop large frames if a MAC configuration declares
jumbo = false?

Since axienet_probe() unconditionally sets ndev->max_mtu = XAE_JUMBO_MTU and
axienet_change_mtu() only validates lp->rxmem:

drivers/net/ethernet/xilinx/xilinx_axienet_main.c:axienet_change_mtu() {
    ...
	if ((new_mtu + VLAN_ETH_HLEN +
		XAE_TRL_SIZE) > lp->rxmem)
		return -EINVAL;

	WRITE_ONCE(ndev->mtu, new_mtu);
    ...
}

The network stack and DMA engine will allow MTUs up to 9000 bytes. However,
when the interface is brought up, axienet_device_reset() will now check
lp->axienet_config->jumbo and refuse to set XAE_OPTION_JUMBO on the hardware. 

If an administrator runs `ip link set ethX mtu 9000` on an interface that
does not support jumbo frames, shouldn't axienet_probe() or
axienet_change_mtu() reject the configuration instead of allowing the stack
to send jumbo frames that the hardware will drop?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261006110550.1990213-1-suraj.gupta2@amd.com?part=1