linux-kernel - Re: [PATCH net] virtio_net: fix xdp_rxq

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Message-ID: <CACGkMEskKF4O7_Dz5=JxB2noVV5qJQusN9DLLzUFc4d149kS7g@mail.gmail.com>
Date:   Wed, 22 Jun 2022 16:06:17 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Stephan Gerhold <stephan.gerhold@...nkonzept.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        virtualization <virtualization@...ts.linux-foundation.org>,
        netdev <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "open list:XDP (eXpress Data Path)" <bpf@...r.kernel.org>
Subject: Re: [PATCH net] virtio_net: fix xdp_rxq_info bug after suspend/resume

On Tue, Jun 21, 2022 at 7:50 PM Stephan Gerhold
<stephan.gerhold@...nkonzept.com> wrote:
>
> The following sequence currently causes a driver bug warning
> when using virtio_net:
>
>   # ip link set eth0 up
>   # echo mem > /sys/power/state (or e.g. # rtcwake -s 10 -m mem)
>   <resume>
>   # ip link set eth0 down
>
>   Missing register, driver bug
>   WARNING: CPU: 0 PID: 375 at net/core/xdp.c:138 xdp_rxq_info_unreg+0x58/0x60
>   Call trace:
>    xdp_rxq_info_unreg+0x58/0x60
>    virtnet_close+0x58/0xac
>    __dev_close_many+0xac/0x140
>    __dev_change_flags+0xd8/0x210
>    dev_change_flags+0x24/0x64
>    do_setlink+0x230/0xdd0
>    ...
>
> This happens because virtnet_freeze() frees the receive_queue
> completely (including struct xdp_rxq_info) but does not call
> xdp_rxq_info_unreg(). Similarly, virtnet_restore() sets up the
> receive_queue again but does not call xdp_rxq_info_reg().
>
> Actually, parts of virtnet_freeze_down() and virtnet_restore_up()
> are almost identical to virtnet_close() and virtnet_open(): only
> the calls to xdp_rxq_info_(un)reg() are missing. This means that
> we can fix this easily and avoid such problems in the future by
> just calling virtnet_close()/open() from the freeze/restore handlers.
>
> Aside from adding the missing xdp_rxq_info calls the only difference
> is that the refill work is only cancelled if netif_running(). However,
> this should not make any functional difference since the refill work
> should only be active if the network interface is actually up.
>
> Fixes: 754b8a21a96d ("virtio_net: setup xdp_rxq_info")
> Signed-off-by: Stephan Gerhold <stephan.gerhold@...nkonzept.com>

Acked-by: Jason Wang <jasowang@...hat.com>

> ---
>  drivers/net/virtio_net.c | 25 ++++++-------------------
>  1 file changed, 6 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index db05b5e930be..969a67970e71 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -2768,7 +2768,6 @@ static const struct ethtool_ops virtnet_ethtool_ops = {
>  static void virtnet_freeze_down(struct virtio_device *vdev)
>  {
>         struct virtnet_info *vi = vdev->priv;
> -       int i;
>
>         /* Make sure no work handler is accessing the device */
>         flush_work(&vi->config_work);
> @@ -2776,14 +2775,8 @@ static void virtnet_freeze_down(struct virtio_device *vdev)
>         netif_tx_lock_bh(vi->dev);
>         netif_device_detach(vi->dev);
>         netif_tx_unlock_bh(vi->dev);
> -       cancel_delayed_work_sync(&vi->refill);
> -
> -       if (netif_running(vi->dev)) {
> -               for (i = 0; i < vi->max_queue_pairs; i++) {
> -                       napi_disable(&vi->rq[i].napi);
> -                       virtnet_napi_tx_disable(&vi->sq[i].napi);
> -               }
> -       }
> +       if (netif_running(vi->dev))
> +               virtnet_close(vi->dev);
>  }
>
>  static int init_vqs(struct virtnet_info *vi);
> @@ -2791,7 +2784,7 @@ static int init_vqs(struct virtnet_info *vi);
>  static int virtnet_restore_up(struct virtio_device *vdev)
>  {
>         struct virtnet_info *vi = vdev->priv;
> -       int err, i;
> +       int err;
>
>         err = init_vqs(vi);
>         if (err)
> @@ -2800,15 +2793,9 @@ static int virtnet_restore_up(struct virtio_device *vdev)
>         virtio_device_ready(vdev);
>
>         if (netif_running(vi->dev)) {
> -               for (i = 0; i < vi->curr_queue_pairs; i++)
> -                       if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL))
> -                               schedule_delayed_work(&vi->refill, 0);
> -
> -               for (i = 0; i < vi->max_queue_pairs; i++) {
> -                       virtnet_napi_enable(vi->rq[i].vq, &vi->rq[i].napi);
> -                       virtnet_napi_tx_enable(vi, vi->sq[i].vq,
> -                                              &vi->sq[i].napi);
> -               }
> +               err = virtnet_open(vi->dev);
> +               if (err)
> +                       return err;
>         }
>
>         netif_tx_lock_bh(vi->dev);
> --
> 2.30.2
>