netdev - Re: [PATCH net 4/4] virtio_net: Update rss when set queue

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Message-ID: <ZyqAovoIOYkNvtys@LQ3V64L9R2>
Date: Tue, 5 Nov 2024 12:31:30 -0800
From: Joe Damato <jdamato@...tly.com>
To: Philo Lu <lulie@...ux.alibaba.com>
Cc: netdev@...r.kernel.org, mst@...hat.com, jasowang@...hat.com,
	xuanzhuo@...ux.alibaba.com, eperezma@...hat.com,
	andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, andrew@...nix.com,
	virtualization@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 4/4] virtio_net: Update rss when set queue

On Mon, Nov 04, 2024 at 04:57:06PM +0800, Philo Lu wrote:
> RSS configuration should be updated with queue number. In particular, it
> should be updated when (1) rss enabled and (2) default rss configuration
> is used without user modification.
> 
> During rss command processing, device updates queue_pairs using
> rss.max_tx_vq. That is, the device updates queue_pairs together with
> rss, so we can skip the sperate queue_pairs update
> (VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET below) and return directly.
> 
> Also remove the `vi->has_rss ?` check when setting vi->rss.max_tx_vq,
> because this is not used in the other hash_report case.
> 
> Fixes: c7114b1249fa ("drivers/net/virtio_net: Added basic RSS support.")
> Signed-off-by: Philo Lu <lulie@...ux.alibaba.com>
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> ---
>  drivers/net/virtio_net.c | 65 +++++++++++++++++++++++++++++++---------
>  1 file changed, 51 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 59d9fdf562e0..189afad3ffaa 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -3394,15 +3394,59 @@ static void virtnet_ack_link_announce(struct virtnet_info *vi)
>  		dev_warn(&vi->dev->dev, "Failed to ack link announce.\n");
>  }
>  
> +static bool virtnet_commit_rss_command(struct virtnet_info *vi);
> +
> +static void virtnet_rss_update_by_qpairs(struct virtnet_info *vi, u16 queue_pairs)
> +{
> +	u32 indir_val = 0;
> +	int i = 0;
> +
> +	for (; i < vi->rss_indir_table_size; ++i) {
> +		indir_val = ethtool_rxfh_indir_default(i, queue_pairs);
> +		vi->rss.indirection_table[i] = indir_val;
> +	}
> +	vi->rss.max_tx_vq = queue_pairs;
> +}
> +
>  static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
>  {
>  	struct virtio_net_ctrl_mq *mq __free(kfree) = NULL;
> -	struct scatterlist sg;
> +	struct virtio_net_ctrl_rss old_rss;
>  	struct net_device *dev = vi->dev;
> +	struct scatterlist sg;
>  
>  	if (!vi->has_cvq || !virtio_has_feature(vi->vdev, VIRTIO_NET_F_MQ))
>  		return 0;
>  
> +	/* Firstly check if we need update rss. Do updating if both (1) rss enabled and
> +	 * (2) no user configuration.
> +	 *
> +	 * During rss command processing, device updates queue_pairs using rss.max_tx_vq. That is,
> +	 * the device updates queue_pairs together with rss, so we can skip the sperate queue_pairs
> +	 * update (VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET below) and return directly.
> +	 */
> +	if (vi->has_rss && !netif_is_rxfh_configured(dev)) {

Does there need to be an error case when:

vi->has_rss && netif_is_rxfh_configured(dev)

to return EINVAL? I noted that other drivers don't let users adjust
the queue count and return error in this case.


> +		memcpy(&old_rss, &vi->rss, sizeof(old_rss));
> +		if (rss_indirection_table_alloc(&vi->rss, vi->rss_indir_table_size)) {
> +			vi->rss.indirection_table = old_rss.indirection_table;
> +			return -ENOMEM;
> +		}
> +
> +		virtnet_rss_update_by_qpairs(vi, queue_pairs);
> +
> +		if (!virtnet_commit_rss_command(vi)) {
> +			/* restore ctrl_rss if commit_rss_command failed */
> +			rss_indirection_table_free(&vi->rss);
> +			memcpy(&vi->rss, &old_rss, sizeof(old_rss));
> +
> +			dev_warn(&dev->dev, "Fail to set num of queue pairs to %d, because committing RSS failed\n",
> +				 queue_pairs);
> +			return -EINVAL;
> +		}
> +		rss_indirection_table_free(&old_rss);
> +		goto succ;
> +	}
> +