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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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