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

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Date: Thu, 28 Mar 2024 09:28:55 +0800
From: Xuan Zhuo <xuanzhuo@...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>,
 hengqi@...ux.alibaba.com,
 "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>
Subject: Re: [PATCH net v2 1/2] virtio_net: Do not set rss_indir if RSS is not supported

On Wed, 27 Mar 2024 06:51:25 -0700, Breno Leitao <leitao@...ian.org> wrote:
> Hello Xuan,
>
> 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.


>
> Thanks for the review,
> Breno