[PATCH net] virtio-net: enable all napis before scheduling refill work
From: Bui Quang Minh <hidden>
Date: 2025-12-08 15:35:06
Also in:
bpf, lkml, virtualization
Subsystem:
networking drivers, the rest, virtio net driver · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, "Michael S. Tsirkin", Jason Wang
Calling napi_disable() on an already disabled napi can cause the
deadlock. In commit 4bc12818b363 ("virtio-net: disable delayed refill
when pausing rx"), to avoid the deadlock, when pausing the RX in
virtnet_rx_pause[_all](), we disable and cancel the delayed refill work.
However, in the virtnet_rx_resume_all(), we enable the delayed refill
work too early before enabling all the receive queue napis.
The deadlock can be reproduced by running
selftests/drivers/net/hw/xsk_reconfig.py with multiqueue virtio-net
device and inserting a cond_resched() inside the for loop in
virtnet_rx_resume_all() to increase the success rate. Because the worker
processing the delayed refilled work runs on the same CPU as
virtnet_rx_resume_all(), a reschedule is needed to cause the deadlock.
In real scenario, the contention on netdev_lock can cause the
reschedule.
This fixes the deadlock by ensuring all receive queue's napis are
enabled before we enable the delayed refill work in
virtnet_rx_resume_all() and virtnet_open().
Fixes: 4bc12818b363 ("virtio-net: disable delayed refill when pausing rx")
Reported-by: Paolo Abeni <pabeni@redhat.com>
Closes: https://netdev-ctrl.bots.linux.dev/logs/vmksft/drv-hw-dbg/results/400961/3-xdp-py/stderr
Signed-off-by: Bui Quang Minh <redacted>
---
drivers/net/virtio_net.c | 59 +++++++++++++++++++---------------------
1 file changed, 28 insertions(+), 31 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 8e04adb57f52..f2b1ea65767d 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c@@ -2858,6 +2858,20 @@ static bool try_fill_recv(struct virtnet_info *vi, struct receive_queue *rq, return err != -ENOMEM; } +static void virtnet_rx_refill_all(struct virtnet_info *vi) +{ + bool schedule_refill = false; + int i; + + enable_delayed_refill(vi); + for (i = 0; i < vi->curr_queue_pairs; i++) + if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL)) + schedule_refill = true; + + if (schedule_refill) + schedule_delayed_work(&vi->refill, 0); +} + static void skb_recv_done(struct virtqueue *rvq) { struct virtnet_info *vi = rvq->vdev->priv;
@@ -3216,19 +3230,14 @@ static int virtnet_open(struct net_device *dev) struct virtnet_info *vi = netdev_priv(dev); int i, err; - enable_delayed_refill(vi); - for (i = 0; i < vi->max_queue_pairs; i++) { - if (i < vi->curr_queue_pairs) - /* Make sure we have some buffers: if oom use wq. */ - if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL)) - schedule_delayed_work(&vi->refill, 0); - err = virtnet_enable_queue_pair(vi, i); if (err < 0) goto err_enable_qp; } + virtnet_rx_refill_all(vi); + if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_STATUS)) { if (vi->status & VIRTIO_NET_S_LINK_UP) netif_carrier_on(vi->dev);
@@ -3463,39 +3472,27 @@ static void virtnet_rx_pause(struct virtnet_info *vi, struct receive_queue *rq) __virtnet_rx_pause(vi, rq); } -static void __virtnet_rx_resume(struct virtnet_info *vi, - struct receive_queue *rq, - bool refill) -{ - bool running = netif_running(vi->dev); - bool schedule_refill = false; - - if (refill && !try_fill_recv(vi, rq, GFP_KERNEL)) - schedule_refill = true; - if (running) - virtnet_napi_enable(rq); - - if (schedule_refill) - schedule_delayed_work(&vi->refill, 0); -} - static void virtnet_rx_resume_all(struct virtnet_info *vi) { int i; - enable_delayed_refill(vi); - for (i = 0; i < vi->max_queue_pairs; i++) { - if (i < vi->curr_queue_pairs) - __virtnet_rx_resume(vi, &vi->rq[i], true); - else - __virtnet_rx_resume(vi, &vi->rq[i], false); + if (netif_running(vi->dev)) { + for (i = 0; i < vi->max_queue_pairs; i++) + virtnet_napi_enable(&vi->rq[i]); + + virtnet_rx_refill_all(vi); } } static void virtnet_rx_resume(struct virtnet_info *vi, struct receive_queue *rq) { - enable_delayed_refill(vi); - __virtnet_rx_resume(vi, rq, true); + if (netif_running(vi->dev)) { + virtnet_napi_enable(rq); + + enable_delayed_refill(vi); + if (!try_fill_recv(vi, rq, GFP_KERNEL)) + schedule_delayed_work(&vi->refill, 0); + } } static int virtnet_rx_resize(struct virtnet_info *vi,
--
2.43.0