linux-kernel - Re: [PATCH net v2 1/2] virtio_net: Do not set rss

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Date: Fri, 29 Mar 2024 10:10:10 +0800
From: Heng Qi <hengqi@...ux.alibaba.com>
To: Breno Leitao <leitao@...ian.org>
Cc: rbc@...a.com, riel@...riel.com,
 "open list:VIRTIO CORE AND NET DRIVERS" <virtualization@...ts.linux.dev>,
 "open list:NETWORKING DRIVERS" <netdev@...r.kernel.org>,
 open list <linux-kernel@...r.kernel.org>, "Michael S. Tsirkin"
 <mst@...hat.com>, Jason Wang <jasowang@...hat.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Subject: Re: [PATCH net v2 1/2] virtio_net: Do not set rss_indir if RSS is not
 supported



在 2024/3/28 下午10:37, Breno Leitao 写道:
>>> On Wed, Mar 27, 2024 at 09:37:43AM +0800, Xuan Zhuo wrote:
>>>> On Tue, 26 Mar 2024 08:19:08 -0700, Breno Leitao <leitao@...ian.org> wrote:
>>>>> Do not set virtnet_info->rss_indir_table_size if RSS is not available
>>>>> for the device.
>>>>>
>>>>> Currently, rss_indir_table_size is set if either has_rss or
>>>>> has_rss_hash_report is available, but, it should only be set if has_rss
>>>>> is set.
>>>>>
>>>>> On the virtnet_set_rxfh(), return an invalid command if the request has
>>>>> indirection table set, but virtnet does not support RSS.
>>>>>
>>>>> Suggested-by: Heng Qi <hengqi@...ux.alibaba.com>
>>>>> Signed-off-by: Breno Leitao <leitao@...ian.org>
>>>>> ---
>>>>>   drivers/net/virtio_net.c | 9 +++++++--
>>>>>   1 file changed, 7 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>>>>> index c22d1118a133..c640fdf28fc5 100644
>>>>> --- a/drivers/net/virtio_net.c
>>>>> +++ b/drivers/net/virtio_net.c
>>>>> @@ -3813,6 +3813,9 @@ static int virtnet_set_rxfh(struct net_device *dev,
>>>>>   	    rxfh->hfunc != ETH_RSS_HASH_TOP)
>>>>>   		return -EOPNOTSUPP;
>>>>>
>>>>> +	if (rxfh->indir && !vi->has_rss)
>>>>> +		return -EINVAL;
>>>>> +
>>>>>   	if (rxfh->indir) {
>>>> Put !vi->has_rss here?
>>> I am not sure I understand the suggestion. Where do you suggest we have
>>> !vi->has_rss?
>>>
>>> If we got this far, we either have:
>>>
>>> a) rxfh->indir set and vi->has_rss is also set
>>> b) rxfh->indir not set. (vi->has_rss could be set or not).
>>
>> This function does two tasks.
>> 1. update indir table
>> 2. update rss key
>>
>> #1 only for has_rss
>> #2 for has_rss or has_rss_hash_report
>>
>>
>> So I would code:
>>
>> 	bool update = false
>>
>> 	if (rxfh->indir) {
>> 		if (!vi->has_rss)
>> 			return -EINVAL;
>>
>> 		for (i = 0; i < vi->rss_indir_table_size; ++i)
>> 			vi->ctrl->rss.indirection_table[i] = rxfh->indir[i];
>>
>> 		update = true
>> 	}
>>
>> 	if (rxfh->key) {
>> 		if (!vi->has_rss && !vi->has_rss_hash_report)
>> 			return -EINVAL;
>>
>> 		memcpy(vi->ctrl->rss.key, rxfh->key, vi->rss_key_size);
>> 		update = true
>> 	}
>>
>>
>> 	if (update)
>> 		virtnet_commit_rss_command(vi);
>>
>> Thanks.
> This is a bit different from the previous proposal, but, I like this one
> approach better. It makes the code easier to read.
>
> How does the full patch looks like?
>
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index c22d1118a133..180f342f1898 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -3807,20 +3807,35 @@ static int virtnet_set_rxfh(struct net_device *dev,
>   			    struct netlink_ext_ack *extack)
>   {
>   	struct virtnet_info *vi = netdev_priv(dev);
> +	bool update = false;
>   	int i;
>   
> +	if (!vi->has_rss && !vi->has_rss_hash_report)
> +		return -EOPNOTSUPP;
> +

I think this two modifications are no longer needed as they have been 
embedded below.

>   	if (rxfh->hfunc != ETH_RSS_HASH_NO_CHANGE &&
>   	    rxfh->hfunc != ETH_RSS_HASH_TOP)
>   		return -EOPNOTSUPP;
>   
>   	if (rxfh->indir) {
> +		if (!vi->has_rss)
> +			return -EINVAL;

-EOPNOTSUPP seems better.

> +
>   		for (i = 0; i < vi->rss_indir_table_size; ++i)
>   			vi->ctrl->rss.indirection_table[i] = rxfh->indir[i];
> +		update = true;
>   	}
> -	if (rxfh->key)
> +
> +	if (rxfh->key) {
> +		if (!vi->has_rss && !vi->has_rss_hash_report)
> +			return -EINVAL;

Same as above. return -EOPNOTSUPP.

Others look good.

Thanks.

> +
>   		memcpy(vi->ctrl->rss.key, rxfh->key, vi->rss_key_size);
> +		update = true;
> +	}
>   
> -	virtnet_commit_rss_command(vi);
> +	if (update)
> +		virtnet_commit_rss_command(vi);
>   
>   	return 0;
>   }
> @@ -4729,13 +4744,15 @@ static int virtnet_probe(struct virtio_device *vdev)
>   	if (virtio_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT))
>   		vi->has_rss_hash_report = true;
>   
> -	if (virtio_has_feature(vdev, VIRTIO_NET_F_RSS))
> +	if (virtio_has_feature(vdev, VIRTIO_NET_F_RSS)) {
>   		vi->has_rss = true;
>   
> -	if (vi->has_rss || vi->has_rss_hash_report) {
>   		vi->rss_indir_table_size =
>   			virtio_cread16(vdev, offsetof(struct virtio_net_config,
>   				rss_max_indirection_table_length));
> +	}
> +
> +	if (vi->has_rss || vi->has_rss_hash_report) {
>   		vi->rss_key_size =
>   			virtio_cread8(vdev, offsetof(struct virtio_net_config, rss_max_key_size));
>