From fcdef3bcbb2c04e06ae89f8faff2cd6416b3a467 Mon Sep 17 00:00:00 2001 From: Bui Quang Minh Date: Tue, 6 Jan 2026 22:04:36 +0700 Subject: [PATCH 1/3] virtio-net: don't schedule delayed refill worker When we fail to refill the receive buffers, we schedule a delayed worker to retry later. However, this worker creates some concurrency issues. For example, when the worker runs concurrently with virtnet_xdp_set, both need to temporarily disable queue's NAPI before enabling again. Without proper synchronization, a deadlock can happen when napi_disable() is called on an already disabled NAPI. That napi_disable() call will be stuck and so will the subsequent napi_enable() call. To simplify the logic and avoid further problems, we will instead retry refilling in the next NAPI poll. Fixes: 4bc12818b363 ("virtio-net: disable delayed refill when pausing rx") Reported-by: Paolo Abeni Closes: https://lore.kernel.org/526b5396-459d-4d02-8635-a222d07b46d7@redhat.com Cc: stable@vger.kernel.org Suggested-by: Xuan Zhuo Signed-off-by: Bui Quang Minh Acked-by: Michael S. Tsirkin Link: https://patch.msgid.link/20260106150438.7425-2-minhquangbui99@gmail.com Signed-off-by: Jakub Kicinski --- drivers/net/virtio_net.c | 47 ++++++++++++++++++++-------------------- 1 file changed, 24 insertions(+), 23 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 22d894101c01..fd8859bd41c7 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -3046,16 +3046,16 @@ static int virtnet_receive(struct receive_queue *rq, int budget, else packets = virtnet_receive_packets(vi, rq, budget, xdp_xmit, &stats); + u64_stats_set(&stats.packets, packets); if (rq->vq->num_free > min((unsigned int)budget, virtqueue_get_vring_size(rq->vq)) / 2) { - if (!try_fill_recv(vi, rq, GFP_ATOMIC)) { - spin_lock(&vi->refill_lock); - if (vi->refill_enabled) - schedule_delayed_work(&vi->refill, 0); - spin_unlock(&vi->refill_lock); - } + if (!try_fill_recv(vi, rq, GFP_ATOMIC)) + /* We need to retry refilling in the next NAPI poll so + * we must return budget to make sure the NAPI is + * repolled. + */ + packets = budget; } - u64_stats_set(&stats.packets, packets); u64_stats_update_begin(&rq->stats.syncp); for (i = 0; i < ARRAY_SIZE(virtnet_rq_stats_desc); i++) { size_t offset = virtnet_rq_stats_desc[i].offset; @@ -3230,9 +3230,10 @@ static int virtnet_open(struct net_device *dev) 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); + /* Pre-fill rq agressively, to make sure we are ready to + * get packets immediately. + */ + try_fill_recv(vi, &vi->rq[i], GFP_KERNEL); err = virtnet_enable_queue_pair(vi, i); if (err < 0) @@ -3472,16 +3473,15 @@ 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 (netif_running(vi->dev)) { + /* Pre-fill rq agressively, to make sure we are ready to get + * packets immediately. + */ + if (refill) + try_fill_recv(vi, rq, GFP_KERNEL); - 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) @@ -3829,11 +3829,12 @@ static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs) } succ: vi->curr_queue_pairs = queue_pairs; - /* virtnet_open() will refill when device is going to up. */ - spin_lock_bh(&vi->refill_lock); - if (dev->flags & IFF_UP && vi->refill_enabled) - schedule_delayed_work(&vi->refill, 0); - spin_unlock_bh(&vi->refill_lock); + if (dev->flags & IFF_UP) { + local_bh_disable(); + for (int i = 0; i < vi->curr_queue_pairs; ++i) + virtqueue_napi_schedule(&vi->rq[i].napi, vi->rq[i].vq); + local_bh_enable(); + } return 0; } From 1e7b90aa7988d90518fa01c398b3487e1fdcb19b Mon Sep 17 00:00:00 2001 From: Bui Quang Minh Date: Tue, 6 Jan 2026 22:04:37 +0700 Subject: [PATCH 2/3] virtio-net: remove unused delayed refill worker Since we switched to retry refilling receive buffer in NAPI poll instead of delayed worker, remove all now unused delayed refill worker code. Acked-by: Michael S. Tsirkin Signed-off-by: Bui Quang Minh Link: https://patch.msgid.link/20260106150438.7425-3-minhquangbui99@gmail.com Signed-off-by: Jakub Kicinski --- drivers/net/virtio_net.c | 86 ---------------------------------------- 1 file changed, 86 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index fd8859bd41c7..9e3770824398 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -441,9 +441,6 @@ struct virtnet_info { /* Packet virtio header size */ u8 hdr_len; - /* Work struct for delayed refilling if we run low on memory. */ - struct delayed_work refill; - /* UDP tunnel support */ bool tx_tnl; @@ -451,12 +448,6 @@ struct virtnet_info { bool rx_tnl_csum; - /* Is delayed refill enabled? */ - bool refill_enabled; - - /* The lock to synchronize the access to refill_enabled */ - spinlock_t refill_lock; - /* Work struct for config space updates */ struct work_struct config_work; @@ -720,20 +711,6 @@ static void virtnet_rq_free_buf(struct virtnet_info *vi, put_page(virt_to_head_page(buf)); } -static void enable_delayed_refill(struct virtnet_info *vi) -{ - spin_lock_bh(&vi->refill_lock); - vi->refill_enabled = true; - spin_unlock_bh(&vi->refill_lock); -} - -static void disable_delayed_refill(struct virtnet_info *vi) -{ - spin_lock_bh(&vi->refill_lock); - vi->refill_enabled = false; - spin_unlock_bh(&vi->refill_lock); -} - static void enable_rx_mode_work(struct virtnet_info *vi) { rtnl_lock(); @@ -2948,42 +2925,6 @@ static void virtnet_napi_disable(struct receive_queue *rq) napi_disable(napi); } -static void refill_work(struct work_struct *work) -{ - struct virtnet_info *vi = - container_of(work, struct virtnet_info, refill.work); - bool still_empty; - int i; - - for (i = 0; i < vi->curr_queue_pairs; i++) { - struct receive_queue *rq = &vi->rq[i]; - - /* - * When queue API support is added in the future and the call - * below becomes napi_disable_locked, this driver will need to - * be refactored. - * - * One possible solution would be to: - * - cancel refill_work with cancel_delayed_work (note: - * non-sync) - * - cancel refill_work with cancel_delayed_work_sync in - * virtnet_remove after the netdev is unregistered - * - wrap all of the work in a lock (perhaps the netdev - * instance lock) - * - check netif_running() and return early to avoid a race - */ - napi_disable(&rq->napi); - still_empty = !try_fill_recv(vi, rq, GFP_KERNEL); - virtnet_napi_do_enable(rq->vq, &rq->napi); - - /* In theory, this can happen: if we don't get any buffers in - * we will *never* try to fill again. - */ - if (still_empty) - schedule_delayed_work(&vi->refill, HZ/2); - } -} - static int virtnet_receive_xsk_bufs(struct virtnet_info *vi, struct receive_queue *rq, int budget, @@ -3226,8 +3167,6 @@ 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) /* Pre-fill rq agressively, to make sure we are ready to @@ -3252,9 +3191,6 @@ static int virtnet_open(struct net_device *dev) return 0; err_enable_qp: - disable_delayed_refill(vi); - cancel_delayed_work_sync(&vi->refill); - for (i--; i >= 0; i--) { virtnet_disable_queue_pair(vi, i); virtnet_cancel_dim(vi, &vi->rq[i].dim); @@ -3448,24 +3384,12 @@ static void virtnet_rx_pause_all(struct virtnet_info *vi) { int i; - /* - * Make sure refill_work does not run concurrently to - * avoid napi_disable race which leads to deadlock. - */ - disable_delayed_refill(vi); - cancel_delayed_work_sync(&vi->refill); for (i = 0; i < vi->max_queue_pairs; i++) __virtnet_rx_pause(vi, &vi->rq[i]); } static void virtnet_rx_pause(struct virtnet_info *vi, struct receive_queue *rq) { - /* - * Make sure refill_work does not run concurrently to - * avoid napi_disable race which leads to deadlock. - */ - disable_delayed_refill(vi); - cancel_delayed_work_sync(&vi->refill); __virtnet_rx_pause(vi, rq); } @@ -3488,7 +3412,6 @@ 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); @@ -3499,7 +3422,6 @@ static void virtnet_rx_resume_all(struct virtnet_info *vi) static void virtnet_rx_resume(struct virtnet_info *vi, struct receive_queue *rq) { - enable_delayed_refill(vi); __virtnet_rx_resume(vi, rq, true); } @@ -3844,10 +3766,6 @@ static int virtnet_close(struct net_device *dev) struct virtnet_info *vi = netdev_priv(dev); int i; - /* Make sure NAPI doesn't schedule refill work */ - disable_delayed_refill(vi); - /* Make sure refill_work doesn't re-enable napi! */ - cancel_delayed_work_sync(&vi->refill); /* Prevent the config change callback from changing carrier * after close */ @@ -5803,7 +5721,6 @@ static int virtnet_restore_up(struct virtio_device *vdev) virtio_device_ready(vdev); - enable_delayed_refill(vi); enable_rx_mode_work(vi); if (netif_running(vi->dev)) { @@ -6560,7 +6477,6 @@ static int virtnet_alloc_queues(struct virtnet_info *vi) if (!vi->rq) goto err_rq; - INIT_DELAYED_WORK(&vi->refill, refill_work); for (i = 0; i < vi->max_queue_pairs; i++) { vi->rq[i].pages = NULL; netif_napi_add_config(vi->dev, &vi->rq[i].napi, virtnet_poll, @@ -6902,7 +6818,6 @@ static int virtnet_probe(struct virtio_device *vdev) INIT_WORK(&vi->config_work, virtnet_config_changed_work); INIT_WORK(&vi->rx_mode_work, virtnet_rx_mode_work); - spin_lock_init(&vi->refill_lock); if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF)) { vi->mergeable_rx_bufs = true; @@ -7166,7 +7081,6 @@ free_failover: net_failover_destroy(vi->failover); free_vqs: virtio_reset_device(vdev); - cancel_delayed_work_sync(&vi->refill); free_receive_page_frags(vi); virtnet_del_vqs(vi); free: From a0c159647e6627496a85e57ca81f8cd6c685564b Mon Sep 17 00:00:00 2001 From: Bui Quang Minh Date: Tue, 6 Jan 2026 22:04:38 +0700 Subject: [PATCH 3/3] virtio-net: clean up __virtnet_rx_pause/resume The delayed refill worker is removed which makes virtnet_rx_pause/resume quite the same as __virtnet_rx_pause/resume. So remove __virtnet_rx_pause/resume and move the code to virtnet_rx_pause/resume. Acked-by: Michael S. Tsirkin Signed-off-by: Bui Quang Minh Link: https://patch.msgid.link/20260106150438.7425-4-minhquangbui99@gmail.com Signed-off-by: Jakub Kicinski --- drivers/net/virtio_net.c | 30 ++++++++++-------------------- 1 file changed, 10 insertions(+), 20 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 9e3770824398..ca92b4a1879c 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -3369,8 +3369,8 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) return NETDEV_TX_OK; } -static void __virtnet_rx_pause(struct virtnet_info *vi, - struct receive_queue *rq) +static void virtnet_rx_pause(struct virtnet_info *vi, + struct receive_queue *rq) { bool running = netif_running(vi->dev); @@ -3385,17 +3385,12 @@ static void virtnet_rx_pause_all(struct virtnet_info *vi) int i; for (i = 0; i < vi->max_queue_pairs; i++) - __virtnet_rx_pause(vi, &vi->rq[i]); + virtnet_rx_pause(vi, &vi->rq[i]); } -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) +static void virtnet_rx_resume(struct virtnet_info *vi, + struct receive_queue *rq, + bool refill) { if (netif_running(vi->dev)) { /* Pre-fill rq agressively, to make sure we are ready to get @@ -3414,17 +3409,12 @@ static void virtnet_rx_resume_all(struct virtnet_info *vi) for (i = 0; i < vi->max_queue_pairs; i++) { if (i < vi->curr_queue_pairs) - __virtnet_rx_resume(vi, &vi->rq[i], true); + virtnet_rx_resume(vi, &vi->rq[i], true); else - __virtnet_rx_resume(vi, &vi->rq[i], false); + virtnet_rx_resume(vi, &vi->rq[i], false); } } -static void virtnet_rx_resume(struct virtnet_info *vi, struct receive_queue *rq) -{ - __virtnet_rx_resume(vi, rq, true); -} - static int virtnet_rx_resize(struct virtnet_info *vi, struct receive_queue *rq, u32 ring_num) { @@ -3438,7 +3428,7 @@ static int virtnet_rx_resize(struct virtnet_info *vi, if (err) netdev_err(vi->dev, "resize rx fail: rx queue index: %d err: %d\n", qindex, err); - virtnet_rx_resume(vi, rq); + virtnet_rx_resume(vi, rq, true); return err; } @@ -5810,7 +5800,7 @@ static int virtnet_rq_bind_xsk_pool(struct virtnet_info *vi, struct receive_queu rq->xsk_pool = pool; - virtnet_rx_resume(vi, rq); + virtnet_rx_resume(vi, rq, true); if (pool) return 0;