From: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Date: Tue, 29 Sep 2020 09:58:06 +0800
Subject: virtio-net: don't disable guest csum when disable LRO
Patch-mainline: v5.9
Git-commit: 1a03b8a35a957f9f38ecb8a97443b7380bbf6a8b
References: git-fixes

Open vSwitch and Linux bridge will disable LRO of the interface
when this interface added to them. Now when disable the LRO, the
virtio-net csum is disable too. That drops the forwarding performance.

Fixes: a02e8964eaf9 ("virtio-net: ethtool configurable LRO")
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/virtio_net.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -63,6 +63,11 @@ static const unsigned long guest_offload
 	VIRTIO_NET_F_GUEST_CSUM
 };
 
+#define GUEST_OFFLOAD_LRO_MASK ((1ULL << VIRTIO_NET_F_GUEST_TSO4) | \
+				(1ULL << VIRTIO_NET_F_GUEST_TSO6) | \
+				(1ULL << VIRTIO_NET_F_GUEST_ECN)  | \
+				(1ULL << VIRTIO_NET_F_GUEST_UFO))
+
 struct virtnet_stat_desc {
 	char desc[ETH_GSTRING_LEN];
 	size_t offset;
@@ -2534,7 +2539,8 @@ static int virtnet_set_features(struct n
 		if (features & NETIF_F_LRO)
 			offloads = vi->guest_offloads_capable;
 		else
-			offloads = 0;
+			offloads = vi->guest_offloads_capable &
+				   ~GUEST_OFFLOAD_LRO_MASK;
 
 		err = virtnet_set_guest_offloads(vi, offloads);
 		if (err)