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SubjectRe: [net-next RFC V5 5/5] virtio_net: support negotiating the number of queues through ctrl vq
On Thu, Jul 05, 2012 at 06:29:54PM +0800, Jason Wang wrote:
> This patch let the virtio_net driver can negotiate the number of queues it
> wishes to use through control virtqueue and export an ethtool interface to let
> use tweak it.
>
> As current multiqueue virtio-net implementation has optimizations on per-cpu
> virtuqueues, so only two modes were support:
>
> - single queue pair mode
> - multiple queue paris mode, the number of queues matches the number of vcpus
>
> The single queue mode were used by default currently due to regression of
> multiqueue mode in some test (especially in stream test).
>
> Since virtio core does not support paritially deleting virtqueues, so during
> mode switching the whole virtqueue were deleted and the driver would re-create
> the virtqueues it would used.
>
> btw. The queue number negotiating were defered to .ndo_open(), this is because
> only after feature negotitaion could we send the command to control virtqueue
> (as it may also use event index).
>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
> drivers/net/virtio_net.c | 171 ++++++++++++++++++++++++++++++++++---------
> include/linux/virtio_net.h | 7 ++
> 2 files changed, 142 insertions(+), 36 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 7410187..3339eeb 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -88,6 +88,7 @@ struct receive_queue {
>
> struct virtnet_info {
> u16 num_queue_pairs; /* # of RX/TX vq pairs */
> + u16 total_queue_pairs;
>
> struct send_queue *sq[MAX_QUEUES] ____cacheline_aligned_in_smp;
> struct receive_queue *rq[MAX_QUEUES] ____cacheline_aligned_in_smp;
> @@ -137,6 +138,8 @@ struct padded_vnet_hdr {
> char padding[6];
> };
>
> +static const struct ethtool_ops virtnet_ethtool_ops;
> +
> static inline int txq_get_qnum(struct virtnet_info *vi, struct virtqueue *vq)
> {
> int ret = virtqueue_get_queue_index(vq);
> @@ -802,22 +805,6 @@ static void virtnet_netpoll(struct net_device *dev)
> }
> #endif
>
> -static int virtnet_open(struct net_device *dev)
> -{
> - struct virtnet_info *vi = netdev_priv(dev);
> - int i;
> -
> - for (i = 0; i < vi->num_queue_pairs; i++) {
> - /* Make sure we have some buffers: if oom use wq. */
> - if (!try_fill_recv(vi->rq[i], GFP_KERNEL))
> - queue_delayed_work(system_nrt_wq,
> - &vi->rq[i]->refill, 0);
> - virtnet_napi_enable(vi->rq[i]);
> - }
> -
> - return 0;
> -}
> -
> /*
> * Send command via the control virtqueue and check status. Commands
> * supported by the hypervisor, as indicated by feature bits, should
> @@ -873,6 +860,43 @@ static void virtnet_ack_link_announce(struct virtnet_info *vi)
> rtnl_unlock();
> }
>
> +static int virtnet_set_queues(struct virtnet_info *vi)
> +{
> + struct scatterlist sg;
> + struct net_device *dev = vi->dev;
> + sg_init_one(&sg, &vi->num_queue_pairs, sizeof(vi->num_queue_pairs));
> +
> + if (!vi->has_cvq)
> + return -EINVAL;
> +
> + if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_MULTIQUEUE,
> + VIRTIO_NET_CTRL_MULTIQUEUE_QNUM, &sg, 1, 0)){
> + dev_warn(&dev->dev, "Fail to set the number of queue pairs to"
> + " %d\n", vi->num_queue_pairs);
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> +static int virtnet_open(struct net_device *dev)
> +{
> + struct virtnet_info *vi = netdev_priv(dev);
> + int i;
> +
> + for (i = 0; i < vi->num_queue_pairs; i++) {
> + /* Make sure we have some buffers: if oom use wq. */
> + if (!try_fill_recv(vi->rq[i], GFP_KERNEL))
> + queue_delayed_work(system_nrt_wq,
> + &vi->rq[i]->refill, 0);
> + virtnet_napi_enable(vi->rq[i]);
> + }
> +
> + virtnet_set_queues(vi);
> +
> + return 0;
> +}
> +
> static int virtnet_close(struct net_device *dev)
> {
> struct virtnet_info *vi = netdev_priv(dev);
> @@ -1013,12 +1037,6 @@ static void virtnet_get_drvinfo(struct net_device *dev,
>
> }
>
> -static const struct ethtool_ops virtnet_ethtool_ops = {
> - .get_drvinfo = virtnet_get_drvinfo,
> - .get_link = ethtool_op_get_link,
> - .get_ringparam = virtnet_get_ringparam,
> -};
> -
> #define MIN_MTU 68
> #define MAX_MTU 65535
>
> @@ -1235,7 +1253,7 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
>
> err:
> if (ret && names)
> - for (i = 0; i < vi->num_queue_pairs * 2; i++)
> + for (i = 0; i < total_vqs * 2; i++)
> kfree(names[i]);
>
> kfree(names);
> @@ -1373,7 +1391,6 @@ static int virtnet_probe(struct virtio_device *vdev)
> mutex_init(&vi->config_lock);
> vi->config_enable = true;
> INIT_WORK(&vi->config_work, virtnet_config_changed_work);
> - vi->num_queue_pairs = num_queue_pairs;
>
> /* If we can receive ANY GSO packets, we must allocate large ones. */
> if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO4) ||
> @@ -1387,6 +1404,10 @@ static int virtnet_probe(struct virtio_device *vdev)
> if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ))
> vi->has_cvq = true;
>
> + /* Use single tx/rx queue pair as default */
> + vi->num_queue_pairs = 1;
> + vi->total_queue_pairs = num_queue_pairs;
> +
> /* Allocate/initialize the rx/tx queues, and invoke find_vqs */
> err = virtnet_setup_vqs(vi);
> if (err)
> @@ -1396,6 +1417,9 @@ static int virtnet_probe(struct virtio_device *vdev)
> virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VLAN))
> dev->features |= NETIF_F_HW_VLAN_FILTER;
>
> + netif_set_real_num_tx_queues(dev, 1);
> + netif_set_real_num_rx_queues(dev, 1);
> +
> err = register_netdev(dev);
> if (err) {
> pr_debug("virtio_net: registering device failed\n");
> @@ -1403,7 +1427,7 @@ static int virtnet_probe(struct virtio_device *vdev)
> }
>
> /* Last of all, set up some receive buffers. */
> - for (i = 0; i < num_queue_pairs; i++) {
> + for (i = 0; i < vi->num_queue_pairs; i++) {
> try_fill_recv(vi->rq[i], GFP_KERNEL);
>
> /* If we didn't even get one input buffer, we're useless. */
> @@ -1474,10 +1498,8 @@ static void __devexit virtnet_remove(struct virtio_device *vdev)
> free_netdev(vi->dev);
> }
>
> -#ifdef CONFIG_PM
> -static int virtnet_freeze(struct virtio_device *vdev)
> +static void virtnet_stop(struct virtnet_info *vi)
> {
> - struct virtnet_info *vi = vdev->priv;
> int i;
>
> /* Prevent config work handler from accessing the device */
> @@ -1493,17 +1515,10 @@ static int virtnet_freeze(struct virtio_device *vdev)
> for (i = 0; i < vi->num_queue_pairs; i++)
> napi_disable(&vi->rq[i]->napi);
>
> -
> - remove_vq_common(vi);
> -
> - flush_work(&vi->config_work);
> -
> - return 0;
> }
>
> -static int virtnet_restore(struct virtio_device *vdev)
> +static int virtnet_start(struct virtnet_info *vi)
> {
> - struct virtnet_info *vi = vdev->priv;
> int err, i;
>
> err = virtnet_setup_vqs(vi);
> @@ -1527,6 +1542,29 @@ static int virtnet_restore(struct virtio_device *vdev)
>
> return 0;
> }
> +
> +#ifdef CONFIG_PM
> +static int virtnet_freeze(struct virtio_device *vdev)
> +{
> + struct virtnet_info *vi = vdev->priv;
> +
> + virtnet_stop(vi);
> +
> + remove_vq_common(vi);
> +
> + flush_work(&vi->config_work);
> +
> + return 0;
> +}
> +
> +static int virtnet_restore(struct virtio_device *vdev)
> +{
> + struct virtnet_info *vi = vdev->priv;
> +
> + virtnet_start(vi);
> +
> + return 0;
> +}
> #endif
>
> static struct virtio_device_id id_table[] = {
> @@ -1560,6 +1598,67 @@ static struct virtio_driver virtio_net_driver = {
> #endif
> };
>
> +static int virtnet_set_channels(struct net_device *dev,
> + struct ethtool_channels *channels)
> +{
> + struct virtnet_info *vi = netdev_priv(dev);
> + u16 queues = channels->rx_count;
> + unsigned status = VIRTIO_CONFIG_S_ACKNOWLEDGE | VIRTIO_CONFIG_S_DRIVER;
> +
> + if (channels->rx_count != channels->tx_count)
> + return -EINVAL;
> + /* Only two modes were support currently */

s/were/are/ ?

> + if (queues != vi->total_queue_pairs && queues != 1)
> + return -EINVAL;

So userspace has to get queue number right. How does it know
what the valid value is?

> + if (!vi->has_cvq)
> + return -EINVAL;
> +
> + virtnet_stop(vi);
> +
> + netif_set_real_num_tx_queues(dev, queues);
> + netif_set_real_num_rx_queues(dev, queues);
> +
> + remove_vq_common(vi);
> + flush_work(&vi->config_work);
> +
> + vi->num_queue_pairs = queues;
> + virtnet_start(vi);
> +
> + vi->vdev->config->finalize_features(vi->vdev);
> +
> + if (virtnet_set_queues(vi))
> + status |= VIRTIO_CONFIG_S_FAILED;
> + else
> + status |= VIRTIO_CONFIG_S_DRIVER_OK;
> +
> + vi->vdev->config->set_status(vi->vdev, status);
> +

Why do we need to tweak status like that?
Can we maybe just roll changes back on error?

> + return 0;
> +}
> +
> +static void virtnet_get_channels(struct net_device *dev,
> + struct ethtool_channels *channels)
> +{
> + struct virtnet_info *vi = netdev_priv(dev);
> +
> + channels->max_rx = vi->total_queue_pairs;
> + channels->max_tx = vi->total_queue_pairs;
> + channels->max_other = 0;
> + channels->max_combined = 0;
> + channels->rx_count = vi->num_queue_pairs;
> + channels->tx_count = vi->num_queue_pairs;
> + channels->other_count = 0;
> + channels->combined_count = 0;
> +}
> +
> +static const struct ethtool_ops virtnet_ethtool_ops = {
> + .get_drvinfo = virtnet_get_drvinfo,
> + .get_link = ethtool_op_get_link,
> + .get_ringparam = virtnet_get_ringparam,
> + .set_channels = virtnet_set_channels,
> + .get_channels = virtnet_get_channels,
> +};
> +
> static int __init init(void)
> {
> return register_virtio_driver(&virtio_net_driver);
> diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
> index 60f09ff..0d21e08 100644
> --- a/include/linux/virtio_net.h
> +++ b/include/linux/virtio_net.h
> @@ -169,4 +169,11 @@ struct virtio_net_ctrl_mac {
> #define VIRTIO_NET_CTRL_ANNOUNCE 3
> #define VIRTIO_NET_CTRL_ANNOUNCE_ACK 0
>
> +/*
> + * Control multiqueue
> + *
> + */
> +#define VIRTIO_NET_CTRL_MULTIQUEUE 4
> + #define VIRTIO_NET_CTRL_MULTIQUEUE_QNUM 0
> +
> #endif /* _LINUX_VIRTIO_NET_H */
> --
> 1.7.1


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