Re: [PATCH net-next] virtio_net: Fix napi_skb_cache_put warning
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2024-07-14 07:38:53
Also in:
lkml, virtualization
On Fri, Jul 12, 2024 at 04:53:25AM -0700, Breno Leitao wrote:
After the commit bdacf3e34945 ("net: Use nested-BH locking for
napi_alloc_cache.") was merged, the following warning began to appear:
WARNING: CPU: 5 PID: 1 at net/core/skbuff.c:1451 napi_skb_cache_put+0x82/0x4b0
__warn+0x12f/0x340
napi_skb_cache_put+0x82/0x4b0
napi_skb_cache_put+0x82/0x4b0
report_bug+0x165/0x370
handle_bug+0x3d/0x80
exc_invalid_op+0x1a/0x50
asm_exc_invalid_op+0x1a/0x20
__free_old_xmit+0x1c8/0x510
napi_skb_cache_put+0x82/0x4b0
__free_old_xmit+0x1c8/0x510
__free_old_xmit+0x1c8/0x510
__pfx___free_old_xmit+0x10/0x10
The issue arises because virtio is assuming it's running in NAPI context
even when it's not, such as in the netpoll case.
To resolve this, modify virtnet_poll_tx() to only set NAPI when budget
is available. Same for virtnet_poll_cleantx(), which always assumed that
it was in a NAPI context.
Fixes: df133f3f9625 ("virtio_net: bulk free tx skbs")
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Breno Leitao <leitao@debian.org>Acked-by: Michael S. Tsirkin <mst@redhat.com> though I'm not sure I understand the connection with bdacf3e34945.
quoted hunk ↗ jump to hunk
--- drivers/net/virtio_net.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 0b4747e81464..fb1331827308 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c@@ -2341,7 +2341,7 @@ static int virtnet_receive(struct receive_queue *rq, int budget, return packets; } -static void virtnet_poll_cleantx(struct receive_queue *rq) +static void virtnet_poll_cleantx(struct receive_queue *rq, int budget) { struct virtnet_info *vi = rq->vq->vdev->priv; unsigned int index = vq2rxq(rq->vq);@@ -2359,7 +2359,7 @@ static void virtnet_poll_cleantx(struct receive_queue *rq) do { virtqueue_disable_cb(sq->vq); - free_old_xmit(sq, txq, true); + free_old_xmit(sq, txq, !!budget); } while (unlikely(!virtqueue_enable_cb_delayed(sq->vq))); if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) {@@ -2404,7 +2404,7 @@ static int virtnet_poll(struct napi_struct *napi, int budget) unsigned int xdp_xmit = 0; bool napi_complete; - virtnet_poll_cleantx(rq); + virtnet_poll_cleantx(rq, budget); received = virtnet_receive(rq, budget, &xdp_xmit); rq->packets_in_napi += received;@@ -2526,7 +2526,7 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget) txq = netdev_get_tx_queue(vi->dev, index); __netif_tx_lock(txq, raw_smp_processor_id()); virtqueue_disable_cb(sq->vq); - free_old_xmit(sq, txq, true); + free_old_xmit(sq, txq, !!budget); if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) { if (netif_tx_queue_stopped(txq)) {-- 2.43.0