netdev - Re: [PATCH net-next v6 2/6] virtio_net: Remove command data from control

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Message-ID: <CANn89iLazVaUCvhPm6RPJJ0owra_oFnx7Fhc8d60gV-65ad3WQ@mail.gmail.com>
Date: Wed, 15 May 2024 14:44:54 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Daniel Jurgens <danielj@...dia.com>
Cc: netdev@...r.kernel.org, mst@...hat.com, jasowang@...hat.com, 
	xuanzhuo@...ux.alibaba.com, virtualization@...ts.linux.dev, 
	davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, jiri@...dia.com
Subject: Re: [PATCH net-next v6 2/6] virtio_net: Remove command data from control_buf

On Fri, May 3, 2024 at 10:25 PM Daniel Jurgens <danielj@...dia.com> wrote:
>
> Allocate memory for the data when it's used. Ideally the struct could
> be on the stack, but we can't DMA stack memory. With this change only
> the header and status memory are shared between commands, which will
> allow using a tighter lock than RTNL.
>
> Signed-off-by: Daniel Jurgens <danielj@...dia.com>
> Reviewed-by: Jiri Pirko <jiri@...dia.com>
> ---
>  drivers/net/virtio_net.c | 124 +++++++++++++++++++++++++++------------
>  1 file changed, 85 insertions(+), 39 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 9cf93a8a4446..451879d570a8 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -368,15 +368,6 @@ struct virtio_net_ctrl_rss {
>  struct control_buf {
>         struct virtio_net_ctrl_hdr hdr;
>         virtio_net_ctrl_ack status;
> -       struct virtio_net_ctrl_mq mq;
> -       u8 promisc;
> -       u8 allmulti;
> -       __virtio16 vid;
> -       __virtio64 offloads;
> -       struct virtio_net_ctrl_coal_tx coal_tx;
> -       struct virtio_net_ctrl_coal_rx coal_rx;
> -       struct virtio_net_ctrl_coal_vq coal_vq;
> -       struct virtio_net_stats_capabilities stats_cap;
>  };
>
>  struct virtnet_info {
> @@ -2828,14 +2819,19 @@ static void virtnet_ack_link_announce(struct virtnet_info *vi)
>
>  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 net_device *dev = vi->dev;
>
>         if (!vi->has_cvq || !virtio_has_feature(vi->vdev, VIRTIO_NET_F_MQ))
>                 return 0;
>
> -       vi->ctrl->mq.virtqueue_pairs = cpu_to_virtio16(vi->vdev, queue_pairs);
> -       sg_init_one(&sg, &vi->ctrl->mq, sizeof(vi->ctrl->mq));
> +       mq = kzalloc(sizeof(*mq), GFP_KERNEL);
> +       if (!mq)
> +               return -ENOMEM;
> +
> +       mq->virtqueue_pairs = cpu_to_virtio16(vi->vdev, queue_pairs);
> +       sg_init_one(&sg, mq, sizeof(*mq));
>
>         if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_MQ,
>                                   VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET, &sg)) {
> @@ -2864,6 +2860,7 @@ static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
>
>  static int virtnet_close(struct net_device *dev)
>  {
> +       u8 *promisc_allmulti  __free(kfree) = NULL;
>         struct virtnet_info *vi = netdev_priv(dev);
>         int i;
>
> @@ -2888,6 +2885,7 @@ static void virtnet_rx_mode_work(struct work_struct *work)
>         struct scatterlist sg[2];
>         struct virtio_net_ctrl_mac *mac_data;
>         struct netdev_hw_addr *ha;
> +       u8 *promisc_allmulti;
>         int uc_count;
>         int mc_count;
>         void *buf;
> @@ -2899,22 +2897,27 @@ static void virtnet_rx_mode_work(struct work_struct *work)
>
>         rtnl_lock();
>
> -       vi->ctrl->promisc = ((dev->flags & IFF_PROMISC) != 0);
> -       vi->ctrl->allmulti = ((dev->flags & IFF_ALLMULTI) != 0);
> +       promisc_allmulti = kzalloc(sizeof(*promisc_allmulti), GFP_ATOMIC);
> +       if (!promisc_allmulti) {

There is a missing rtnl_unlock() here ?

> +               dev_warn(&dev->dev, "Failed to set RX mode, no memory.\n");
> +               return;
> +       }
>
>