On Fri, Jun 05, 2026 at 07:40:44PM +0000, Samuel Moelius wrote:
> The virtio_net.napi_weight module parameter is signed and is copied
> directly into the RX NAPI weight after netif_napi_add_config().
>
> A value of -1 lets virtnet_poll() run with a negative budget. The RX
> loop processes no packets, the unsigned received-vs-budget comparison
> completes NAPI, and the NAPI core reports:
>
> NAPI poll function virtnet_poll returned 0, exceeding its budget of -1
>
> The device then repeatedly drops receive progress under stock QEMU
> virtio-net traffic.
>
> Normalize non-positive values to the default NAPI weight before
> assigning the RX and TX NAPI weights. TX NAPI can still be disabled
> through the separate napi_tx parameter, which intentionally sets the TX
> weight to zero.
>
> Assisted-by: Codex:gpt-5.5-cyber-preview
> Signed-off-by: Samuel Moelius <[email protected]>
Why should we bother working around admin errors in the kernel?
Leave it for the userspace tooling which can at least provide
useful diagnostics.
> ---
> drivers/net/virtio_net.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index f4adcfee7a80..667026607cfa 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -6481,6 +6481,7 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
> static int virtnet_alloc_queues(struct virtnet_info *vi)
> {
> int i;
> + int weight = napi_weight > 0 ? napi_weight : NAPI_POLL_WEIGHT;
>
> if (vi->has_cvq) {
> vi->ctrl = kzalloc_obj(*vi->ctrl);
> @@ -6500,10 +6501,10 @@ static int virtnet_alloc_queues(struct virtnet_info
> *vi)
> vi->rq[i].pages = NULL;
> netif_napi_add_config(vi->dev, &vi->rq[i].napi, virtnet_poll,
> i);
> - vi->rq[i].napi.weight = napi_weight;
> + vi->rq[i].napi.weight = weight;
> netif_napi_add_tx_weight(vi->dev, &vi->sq[i].napi,
> virtnet_poll_tx,
> - napi_tx ? napi_weight : 0);
> + napi_tx ? weight : 0);
>
> sg_init_table(vi->rq[i].sg, ARRAY_SIZE(vi->rq[i].sg));
> ewma_pkt_len_init(&vi->rq[i].mrg_avg_pkt_len);
> --
> 2.43.0
