netdev - Re: [PATCH v2,net] hv_netvsc: Fix tx_table init in rndis_set

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Date:   Sat, 14 Dec 2019 11:30:25 -0800
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Haiyang Zhang <haiyangz@...rosoft.com>
Cc:     sashal@...nel.org, linux-hyperv@...r.kernel.org,
        netdev@...r.kernel.org, kys@...rosoft.com, sthemmin@...rosoft.com,
        olaf@...fle.de, vkuznets@...hat.com, davem@...emloft.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2,net] hv_netvsc: Fix tx_table init in
 rndis_set_subchannel()

On Wed, 11 Dec 2019 14:26:27 -0800, Haiyang Zhang wrote:
> Host can provide send indirection table messages anytime after RSS is
> enabled by calling rndis_filter_set_rss_param(). So the host provided
> table values may be overwritten by the initialization in
> rndis_set_subchannel().
> 
> To prevent this problem, move the tx_table initialization before calling
> rndis_filter_set_rss_param().
> 
> Fixes: a6fb6aa3cfa9 ("hv_netvsc: Set tx_table to equal weight after subchannels open")
> Signed-off-by: Haiyang Zhang <haiyangz@...rosoft.com>

Applied, but there are two more problems with this code:
 - you should not reset the indirection table if it was configured by
   the user to something other than the default (use the
   netif_is_rxfh_configured() helper to check for that)
 - you should use the ethtool_rxfh_indir_default() wrapper

Please fix the former problem in the net tree, and after net is merged
into linux/master and net-next in a week or two please follow up with
the fix for the latter for net-next.

> diff --git a/drivers/net/hyperv/rndis_filter.c b/drivers/net/hyperv/rndis_filter.c
> index 206b4e7..05bc5ec8 100644
> --- a/drivers/net/hyperv/rndis_filter.c
> +++ b/drivers/net/hyperv/rndis_filter.c
> @@ -1171,6 +1171,9 @@ int rndis_set_subchannel(struct net_device *ndev,
>  	wait_event(nvdev->subchan_open,
>  		   atomic_read(&nvdev->open_chn) == nvdev->num_chn);
>  
> +	for (i = 0; i < VRSS_SEND_TAB_SIZE; i++)
> +		ndev_ctx->tx_table[i] = i % nvdev->num_chn;
> +
>  	/* ignore failures from setting rss parameters, still have channels */
>  	if (dev_info)
>  		rndis_filter_set_rss_param(rdev, dev_info->rss_key);
> @@ -1180,9 +1183,6 @@ int rndis_set_subchannel(struct net_device *ndev,
>  	netif_set_real_num_tx_queues(ndev, nvdev->num_chn);
>  	netif_set_real_num_rx_queues(ndev, nvdev->num_chn);
>  
> -	for (i = 0; i < VRSS_SEND_TAB_SIZE; i++)
> -		ndev_ctx->tx_table[i] = i % nvdev->num_chn;
> -
>  	return 0;
>  }
>