Re: [PATCH net-next v2] gve: Add RSS cache for non RSS device option scenario

[Simon Horman <horms@kernel.org>]

On Tue, Feb 04, 2025 at 01:31:21PM -0800, Jeroen de Borst wrote:
> From: Ziwei Xiao <ziweixiao@google.com>
> 
> Not all the devices have the capability for the driver to query for the
> registered RSS configuration. The driver can discover this by checking
> the relevant device option during setup. If it cannot, the driver needs
> to store the RSS config cache and directly return such cache when
> queried by the ethtool. RSS config is inited when driver probes. Also the
> default RSS config will be adjusted when there is RX queue count change.
> 
> At this point, only keys of GVE_RSS_KEY_SIZE and indirection tables of
> GVE_RSS_INDIR_SIZE are supported.
> 
> Signed-off-by: Ziwei Xiao <ziweixiao@google.com>
> Reviewed-by: Harshitha Ramamurthy <hramamurthy@google.com>
> Reviewed-by: Willem de Bruijn <willemb@google.com>
> Signed-off-by: Praveen Kaligineedi <pkaligineedi@google.com>
> Signed-off-by: Jeroen de Borst <jeroend@google.com>
> ---
> Changes in v2:
>  - Change to initialize RSS config when the driver is up instead of
>    doing that when the user setting the RSS.(Jakub Kicinski)
>  - Use NL_SET_ERR_MSG_MOD to log errors when there is extack
>    available.(Jakub Kicinski)
>  - Use ethtool_rxfh_indir_default to set default RSS indir
>    table.(Jakub Kicinski)
>  - Adjust the default RSS config when there is RX queue count change to
>    ensure the default RSS config is correct.
> 
>  drivers/net/ethernet/google/gve/gve.h         | 16 +++-
>  drivers/net/ethernet/google/gve/gve_adminq.c  | 64 ++++++++++---
>  drivers/net/ethernet/google/gve/gve_ethtool.c | 60 ++++++++++--
>  drivers/net/ethernet/google/gve/gve_main.c    | 92 ++++++++++++++++++-
>  4 files changed, 209 insertions(+), 23 deletions(-)

...

> diff --git a/drivers/net/ethernet/google/gve/gve_ethtool.c b/drivers/net/ethernet/google/gve/gve_ethtool.c
> index bdfc6e77b2af..efcafc607b2a 100644
> --- a/drivers/net/ethernet/google/gve/gve_ethtool.c
> +++ b/drivers/net/ethernet/google/gve/gve_ethtool.c
> @@ -482,6 +482,7 @@ static int gve_set_channels(struct net_device *netdev,
>  	struct ethtool_channels old_settings;
>  	int new_tx = cmd->tx_count;
>  	int new_rx = cmd->rx_count;
> +	bool reset_rss;
>  
>  	gve_get_channels(netdev, &old_settings);
>  
> @@ -498,16 +499,14 @@ static int gve_set_channels(struct net_device *netdev,
>  		return -EINVAL;
>  	}
>  
> -	if (!netif_running(netdev)) {
> -		priv->tx_cfg.num_queues = new_tx;
> -		priv->rx_cfg.num_queues = new_rx;
> -		return 0;
> -	}
> +	if (new_rx != priv->rx_cfg.num_queues &&
> +	    priv->cache_rss_config && !netif_is_rxfh_configured(netdev))
> +		reset_rss = true;

Hi Jerome,

This is not a full review (which I was working on but ran out of time for now).
But, if the condition above is not met then reset_rss will be used
uninitialised below.

Flagged by W=1 build with clang-19.

>  
>  	new_tx_cfg.num_queues = new_tx;
>  	new_rx_cfg.num_queues = new_rx;
>  
> -	return gve_adjust_queues(priv, new_rx_cfg, new_tx_cfg);
> +	return gve_adjust_queues(priv, new_rx_cfg, new_tx_cfg, reset_rss);
>  }
>  
>  static void gve_get_ringparam(struct net_device *netdev,

...

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