On Thu, 2012-07-05 at 18:29 +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).

[...]

+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;

[...]

+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;
+}

[...]

It looks like the queue-pairs should be treated as 'combined channels',
not separate RX and TX channels.  Also you don't need to clear the other
members; you can assume that the ethtool core will zero-initialise
structures for 'get' operations.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.