netdev - Re: [v2 Patch 2/2] mlx4: add dynamic LRO disable support

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Message-ID: <4C173B57.70601@redhat.com>
Date:	Tue, 15 Jun 2010 16:35:35 +0800
From:	Cong Wang <amwang@...hat.com>
To:	Stanislaw Gruszka <sgruszka@...hat.com>
CC:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	nhorman@...hat.com, herbert.xu@...hat.com,
	bhutchings@...arflare.com, Ramkrishna.Vepa@...r.com
Subject: Re: [v2 Patch 2/2] mlx4: add dynamic LRO disable support

On 06/09/10 19:05, Stanislaw Gruszka wrote:
> On Wed, Jun 09, 2010 at 06:05:34AM -0400, Amerigo Wang wrote:
>> diff --git a/drivers/net/mlx4/en_ethtool.c b/drivers/net/mlx4/en_ethtool.c
>> index d5afd03..2c77805 100644
>> --- a/drivers/net/mlx4/en_ethtool.c
>> +++ b/drivers/net/mlx4/en_ethtool.c
>> @@ -387,6 +387,37 @@ static void mlx4_en_get_ringparam(struct net_device *dev,
>>   	param->tx_pending = mdev->profile.prof[priv->port].tx_ring_size;
>>   }
>>
>> +static int mlx4_ethtool_op_set_flags(struct net_device *dev, u32 data)
>> +{
>> +	struct mlx4_en_priv *priv = netdev_priv(dev);
>> +	struct mlx4_en_dev *mdev = priv->mdev;
>> +	int rc = 0;
>> +	int changed = 0;
>> +
>> +	if (data&  ETH_FLAG_LRO) {
>> +		if (!(dev->features&  NETIF_F_LRO)) {
>> +			dev->features |= NETIF_F_LRO;
>> +			changed = 1;
>> +			mdev->profile.num_lro = min_t(int, num_lro , MLX4_EN_MAX_LRO_DESCRIPTORS);
>
> I do not understand why you override mdev->profile.num_lro in v2 patch.
> If in Rx patch NETIF_F_LRO flag is used we do not need this IMHO.

Oh, I thought you meant this in our previous disccussion. :-/
I will drop this line.

>
>> +		}
>> +	} else if (dev->features&  NETIF_F_LRO) {
>> +		dev->features&= ~NETIF_F_LRO;
>> +		changed = 1;
>> +		mdev->profile.num_lro = 0;
>> +	}
> [snip]
>>   const struct ethtool_ops mlx4_en_ethtool_ops = {
>>   	.get_drvinfo = mlx4_en_get_drvinfo,
>>   	.get_settings = mlx4_en_get_settings,
>> @@ -415,7 +446,7 @@ const struct ethtool_ops mlx4_en_ethtool_ops = {
>>   	.get_ringparam = mlx4_en_get_ringparam,
>>   	.set_ringparam = mlx4_en_set_ringparam,
>>   	.get_flags = ethtool_op_get_flags,
>> -	.set_flags = ethtool_op_set_flags,
>> +	.set_flags = mlx4_ethtool_op_set_flags,
>>   };
>
> Since we modify .set_flags, please assure we return -EOPNOTSUPP
> if someone will try to setup ETH_FLAG_NTUPLE and ETH_FLAG_RXHASH.


Yeah, good point!

>
> BTW: seems default ethtool_op_set_flags introduce a bug on many
> devices regarding ETH_FLAG_RXHASH. I think default should
> be EOPNOTSUPP, and these few devices that actually support RXHASH
> should have custom ethtool_ops->set_flags

Hmm, you mean this?

  if (data & ETH_FLAG_RXHASH)
+    if (!ops->set_flags)
+        return -EOPNOTSUPP;
....

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