netdev - Re: [PATCH net] virtio_net: Avoid sending unnecessary vq coalescing commands

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Message-ID: <CAJaqyWd+euHy1S_eaxTEY3v9QmAH6pCSG=CnRiZJuNE07=mMTw@mail.gmail.com>
Date: Tue, 30 Jul 2024 13:04:23 +0200
From: Eugenio Perez Martin <eperezma@...hat.com>
To: Heng Qi <hengqi@...ux.alibaba.com>
Cc: netdev@...r.kernel.org, "Michael S. Tsirkin" <mst@...hat.com>, 
	Jason Wang <jasowang@...hat.com>, virtualization@...ts.linux.dev, 
	"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] virtio_net: Avoid sending unnecessary vq coalescing commands

On Mon, Jul 29, 2024 at 2:48 PM Heng Qi <hengqi@...ux.alibaba.com> wrote:
>
> From the virtio spec:
>
>         The driver MUST have negotiated the VIRTIO_NET_F_VQ_NOTF_COAL
>         feature when issuing commands VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET
>         and VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET.
>
> The driver must not send vq notification coalescing commands if
> VIRTIO_NET_F_VQ_NOTF_COAL is not negotiated. This limitation of course
> applies to vq resize.
>
> Fixes: f61fe5f081cf ("virtio-net: fix the vq coalescing setting for vq resize")

Acked-by: Eugenio Pérez <eperezma@...hat.com>

> Signed-off-by: Heng Qi <hengqi@...ux.alibaba.com>
> ---
>  drivers/net/virtio_net.c | 29 +++++++++++++++++------------
>  1 file changed, 17 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 0383a3e136d6..eb115e807882 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -3708,6 +3708,7 @@ static int virtnet_set_ringparam(struct net_device *dev,
>         u32 rx_pending, tx_pending;
>         struct receive_queue *rq;
>         struct send_queue *sq;
> +       u32 pkts, usecs;
>         int i, err;
>
>         if (ring->rx_mini_pending || ring->rx_jumbo_pending)
> @@ -3740,11 +3741,13 @@ static int virtnet_set_ringparam(struct net_device *dev,
>                          * through the VIRTIO_NET_CTRL_NOTF_COAL_TX_SET command, or, if the driver
>                          * did not set any TX coalescing parameters, to 0.
>                          */
> -                       err = virtnet_send_tx_ctrl_coal_vq_cmd(vi, i,
> -                                                              vi->intr_coal_tx.max_usecs,
> -                                                              vi->intr_coal_tx.max_packets);
> -                       if (err)
> -                               return err;
> +                       if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL)) {
> +                               usecs = vi->intr_coal_tx.max_usecs;
> +                               pkts = vi->intr_coal_tx.max_packets;
> +                               err = virtnet_send_tx_ctrl_coal_vq_cmd(vi, i, usecs, pkts);
> +                               if (err)
> +                                       return err;
> +                       }
>                 }
>
>                 if (ring->rx_pending != rx_pending) {
> @@ -3753,13 +3756,15 @@ static int virtnet_set_ringparam(struct net_device *dev,
>                                 return err;
>
>                         /* The reason is same as the transmit virtqueue reset */
> -                       mutex_lock(&vi->rq[i].dim_lock);
> -                       err = virtnet_send_rx_ctrl_coal_vq_cmd(vi, i,
> -                                                              vi->intr_coal_rx.max_usecs,
> -                                                              vi->intr_coal_rx.max_packets);
> -                       mutex_unlock(&vi->rq[i].dim_lock);
> -                       if (err)
> -                               return err;
> +                       if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL)) {
> +                               usecs = vi->intr_coal_rx.max_usecs;
> +                               pkts = vi->intr_coal_rx.max_packets;
> +                               mutex_lock(&vi->rq[i].dim_lock);
> +                               err = virtnet_send_rx_ctrl_coal_vq_cmd(vi, i, usecs, pkts);
> +                               mutex_unlock(&vi->rq[i].dim_lock);
> +                               if (err)
> +                                       return err;
> +                       }
>                 }
>         }
>
> --
> 2.32.0.3.g01195cf9f
>