netdev - [PATCH net] virtio_net: fix xdp_rxq_info bug after suspend/resume

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Date:   Tue, 21 Jun 2022 13:48:44 +0200
From:   Stephan Gerhold <stephan.gerhold@...nkonzept.com>
To:     "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>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>
Cc:     Stephan Gerhold <stephan.gerhold@...nkonzept.com>,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: [PATCH net] virtio_net: fix xdp_rxq_info bug after suspend/resume

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>
---
 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