[PATCH 3.16 343/370] netvsc: reduce maximum GSO size

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From	Ben Hutchings <ben@decadent.org.uk>
Newsgroups	linux.kernel
Subject	[PATCH 3.16 343/370] netvsc: reduce maximum GSO size
Date	Fri, 10 Mar 2017 14:30:02 +0100
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3.16.42-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: stephen hemminger <stephen@networkplumber.org>

[ Upstream commit a50af86dd49ee1851d1ccf06dd0019c05b95e297 ]

Hyper-V (and Azure) support using NVGRE which requires some extra space
for encapsulation headers. Because of this the largest allowed TSO
packet is reduced.

For older releases, hard code a fixed reduced value.  For next release,
there is a better solution which uses result of host offload
negotiation.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/net/hyperv/netvsc_drv.c | 3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -47,6 +47,9 @@ struct net_device_context {
 	struct work_struct work;
 };
 
+/* Restrict GSO size to account for NVGRE */
+#define NETVSC_GSO_MAX_SIZE	62768
+
 #define RING_SIZE_MIN 64
 static int ring_size = 128;
 module_param(ring_size, int, S_IRUGO);
@@ -839,6 +842,7 @@ static int netvsc_probe(struct hv_device
 	nvdev = hv_get_drvdata(dev);
 	netif_set_real_num_tx_queues(net, nvdev->num_chn);
 	netif_set_real_num_rx_queues(net, nvdev->num_chn);
+	netif_set_gso_max_size(net, NETVSC_GSO_MAX_SIZE);
 
 	ret = register_netdev(net);
 	if (ret != 0) {

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[PATCH 3.16 343/370] netvsc: reduce maximum GSO size Ben Hutchings <ben@decadent.org.uk> - 2017-03-10 14:30 +0100

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