6.14-stable review patch. If anyone has any objections, please let me know.
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From: Jakub Kicinski kuba@kernel.org
[ Upstream commit 1e20324b23f0afba27997434fb978f1e4a1dbcb6 ]
Commit 4bc12818b363 ("virtio-net: disable delayed refill when pausing rx") fixed a deadlock between reconfig paths and refill work trying to disable the same NAPI instance. The refill work can't run in parallel with reconfig because trying to double-disable a NAPI instance causes a stall under the instance lock, which the reconfig path needs to re-enable the NAPI and therefore unblock the stalled thread.
There are two cases where we re-enable refill too early. One is in the virtnet_set_queues() handler. We call it when installing XDP:
virtnet_rx_pause_all(vi); ... virtnet_napi_tx_disable(..); ... virtnet_set_queues(..); ... virtnet_rx_resume_all(..);
We want the work to be disabled until we call virtnet_rx_resume_all(), but virtnet_set_queues() kicks it before NAPIs were re-enabled.
The other case is a more trivial case of mis-ordering in __virtnet_rx_resume() found by code inspection.
Taking the spin lock in virtnet_set_queues() (requested during review) may be unnecessary as we are under rtnl_lock and so are all paths writing to ->refill_enabled.
Acked-by: Michael S. Tsirkin mst@redhat.com Reviewed-by: Bui Quang Minh minhquangbui99@gmail.com Fixes: 4bc12818b363 ("virtio-net: disable delayed refill when pausing rx") Fixes: 413f0271f396 ("net: protect NAPI enablement with netdev_lock()") Link: https://patch.msgid.link/20250430163758.3029367-1-kuba@kernel.org Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/virtio_net.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 3e4896d9537ee..2c3c6e8e3f35b 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -3359,12 +3359,15 @@ static void __virtnet_rx_resume(struct virtnet_info *vi, bool refill) { bool running = netif_running(vi->dev); + bool schedule_refill = false;
if (refill && !try_fill_recv(vi, rq, GFP_KERNEL)) - schedule_delayed_work(&vi->refill, 0); - + 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) @@ -3699,8 +3702,10 @@ 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. */ - if (dev->flags & IFF_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);
return 0; }