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SubjectRe: [net-next RFC V5 5/5] virtio_net: support negotiating the number of queues through ctrl vq
On 07/20/2012 08:33 PM, Michael S. Tsirkin wrote:
> 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/ ?

Ok.
>
>> + 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?

Usespace could query the number through ethtool -l (virtnet_get_channels()).
>
>> + 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?

Because remove_vq_common() reset the device. Since virtio core api does
not support remove a specified number of virtqueues, it's the only
method when we change the number of queues.
> Can we maybe just roll changes back on error?

Not easy, we reset and detroy previous virtqueues and create new ones.
>> + 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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