If the device does not respond to a request for a long time, then control vq polling elevates CPU utilization, a problem that exacerbates with more command requests.
Enabling control vq's irq is advantageous for the guest, and this still doesn't support concurrent requests. This code is basically from Jason: https://lore.kernel.org/all/20230413064027.13267-3-jasow...@redhat.com/ Suggested-by: Jason Wang <jasow...@redhat.com> Signed-off-by: Heng Qi <hen...@linux.alibaba.com> --- drivers/net/virtio_net.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 4a802c0ea2cb..9b556ce89546 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -418,6 +418,9 @@ struct virtnet_info { /* Lock to protect the control VQ */ struct mutex cvq_lock; + /* Wait for the device to complete the cvq request. */ + struct completion completion; + /* Host can handle any s/g split between our header and packet data */ bool any_header_sg; @@ -664,6 +667,13 @@ static bool virtqueue_napi_complete(struct napi_struct *napi, return false; } +static void virtnet_cvq_done(struct virtqueue *cvq) +{ + struct virtnet_info *vi = cvq->vdev->priv; + + complete(&vi->completion); +} + static void skb_xmit_done(struct virtqueue *vq) { struct virtnet_info *vi = vq->vdev->priv; @@ -2721,14 +2731,8 @@ static bool virtnet_send_command_reply(struct virtnet_info *vi, u8 class, u8 cmd if (unlikely(!virtqueue_kick(vi->cvq))) goto unlock; - /* Spin for a response, the kick causes an ioport write, trapping - * into the hypervisor, so the request should be handled immediately. - */ - while (!virtqueue_get_buf(vi->cvq, &tmp) && - !virtqueue_is_broken(vi->cvq)) { - cond_resched(); - cpu_relax(); - } + wait_for_completion(&vi->completion); + virtqueue_get_buf(vi->cvq, &tmp); unlock: mutex_unlock(&vi->cvq_lock); @@ -5312,7 +5316,7 @@ static int virtnet_find_vqs(struct virtnet_info *vi) /* Parameters for control virtqueue, if any */ if (vi->has_cvq) { - callbacks[total_vqs - 1] = NULL; + callbacks[total_vqs - 1] = virtnet_cvq_done; names[total_vqs - 1] = "control"; } @@ -5832,6 +5836,7 @@ static int virtnet_probe(struct virtio_device *vdev) if (vi->has_rss || vi->has_rss_hash_report) virtnet_init_default_rss(vi); + init_completion(&vi->completion); enable_rx_mode_work(vi); /* serialize netdev register + virtio_device_ready() with ndo_open() */ -- 2.32.0.3.g01195cf9f
