hv_netvsc: Set vRSS with num_chn in RNDIS filter

Uses device_info->num_chn to pass user provided number of vRSS
queues (from ethtool --set-channels) to rndis_filter_device_add. If
nonzero and less than the maximum, set net_device->num_chn to the given
value; else default to prior algorithm.

Always initialize struct device_info to 0, otherwise not all its fields
are guaranteed to be 0, which is necessary when checking if num_chn has
been purposefully set.
Signed-off-by: Andrew Schwartzmeyer <andschwa@microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/hyperv/hyperv_net.h

@@ -162,6 +162,7 @@ struct netvsc_device_info {
 	bool link_state;	/* 0 - link up, 1 - link down */
 	int  ring_size;
 	u32  max_num_vrss_chns;
+	u32  num_chn;
 };
 
 enum rndis_device_state {

drivers/net/hyperv/netvsc_drv.c

@@ -799,6 +799,8 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
 
 	ndevctx->device_ctx = hdev;
 	hv_set_drvdata(hdev, ndev);
+
+	memset(&device_info, 0, sizeof(device_info));
 	device_info.ring_size = ring_size;
 	device_info.max_num_vrss_chns = max_num_vrss_chns;
 	rndis_filter_device_add(hdev, &device_info);
@@ -1022,6 +1024,7 @@ static int netvsc_probe(struct hv_device *dev,
 	net->needed_headroom = max_needed_headroom;
 
 	/* Notify the netvsc driver of the new device */
+	memset(&device_info, 0, sizeof(device_info));
 	device_info.ring_size = ring_size;
 	device_info.max_num_vrss_chns = max_num_vrss_chns;
 	ret = rndis_filter_device_add(dev, &device_info);

drivers/net/hyperv/rndis_filter.c

@@ -1125,7 +1125,12 @@ int rndis_filter_device_add(struct hv_device *dev,
 	 */
 	node_cpu_mask = cpumask_of_node(cpu_to_node(dev->channel->target_cpu));
 	num_possible_rss_qs = cpumask_weight(node_cpu_mask);
-	net_device->num_chn = min(num_possible_rss_qs, num_rss_qs);
+
+	/* We will use the given number of channels if available. */
+	if (device_info->num_chn && device_info->num_chn < net_device->max_chn)
+		net_device->num_chn = device_info->num_chn;
+	else
+		net_device->num_chn = min(num_possible_rss_qs, num_rss_qs);
 
 	num_rss_qs = net_device->num_chn - 1;
 	net_device->num_sc_offered = num_rss_qs;