On Wed, Jun 24, 2026 at 03:02:06PM +0800, Longjun Tang wrote:
> From: Longjun Tang <[email protected]>
>
> When busy-poll is active, napi_schedule_prep() returns false in
> virtqueue_napi_schedule(), so virtqueue_disable_cb() is skipped.
> The device may keep firing irqs until reaches virtqueue_napi_complete().
> Under load (received == budget), it will lead to a large number
> of spurious interrupts.
>
> Fix it by disabling the callback at the virtnet_poll() entry. This keeps
> the callback off while we poll and re-enable
and it is re-enabled
> by virtqueue_napi_complete()
> when going idle.
>
> Fixes: ceef438d613f ("virtio_net: remove custom busy_poll")
> Acked-by: Michael S. Tsirkin <[email protected]>
> Signed-off-by: Longjun Tang <[email protected]>
>
> ---
> V1 -> V2: Remain agnostic to busy polling
> V2 -> V3: Add fixes tag
> ---
> drivers/net/virtio_net.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index f4adcfee7a80..0a11f2b32500 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -3008,6 +3008,11 @@ static int virtnet_poll(struct napi_struct *napi, int
> budget)
> unsigned int xdp_xmit = 0;
> bool napi_complete;
>
> + /* Keep callbacks suppressed for the duration of this poll,
> + * busy-poll need.
I don't know what "busy-poll need" means. Just drop this part?
In fact, the whole comment can go, we know virtqueue_disable_cb
disables callbacks.
> + */
> + virtqueue_disable_cb(rq->vq);
> +
> virtnet_poll_cleantx(rq, budget);
>
> received = virtnet_receive(rq, budget, &xdp_xmit);
> --
> 2.43.0
