[PATCH 5.4 38/61] virtio-net: use NETIF_F_GRO_HW instead of NETIF_F_LRO

Sasha Levin
2021-08-24T17:17:13Z

From: Jason Wang <jasowang@redhat.com>

[ Upstream commit dbcf24d153884439dad30484a0e3f02350692e4c ]

Commit a02e8964eaf92 ("virtio-net: ethtool configurable LRO")
maps LRO to virtio guest offloading features and allows the
administrator to enable and disable those features via ethtool.

This leads to several issues:

- For a device that doesn't support control guest offloads, the "LRO"
can't be disabled triggering WARN in dev_disable_lro() when turning
off LRO or when enabling forwarding bridging etc.

- For a device that supports control guest offloads, the guest
offloads are disabled in cases of bridging, forwarding etc slowing
down the traffic.

Fix this by using NETIF_F_GRO_HW instead. Though the spec does not
guarantee packets to be re-segmented as the original ones,
we can add that to the spec, possibly with a flag for devices to
differentiate between GRO and LRO.

Further, we never advertised LRO historically before a02e8964eaf92
("virtio-net: ethtool configurable LRO") and so bridged/forwarded
configs effectively always relied on virtio receive offloads behaving
like GRO - thus even if this breaks any configs it is at least not
a regression.

Fixes: a02e8964eaf92 ("virtio-net: ethtool configurable LRO")
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reported-by: Ivan <ivan@prestigetransportation.com>
Tested-by: Ivan <ivan@prestigetransportation.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/virtio_net.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 36f8aeb113a8..37c2cecd1e50 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -63,7 +63,7 @@ static const unsigned long guest_offloads[] = {
VIRTIO_NET_F_GUEST_CSUM
};

-#define GUEST_OFFLOAD_LRO_MASK ((1ULL << VIRTIO_NET_F_GUEST_TSO4) | \
+#define GUEST_OFFLOAD_GRO_HW_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))
@@ -2493,7 +2493,7 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ECN) ||
virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_UFO) ||
virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))) {
- NL_SET_ERR_MSG_MOD(extack, "Can't set XDP while host is implementing LRO/CSUM, disable LRO/CSUM first");
+ NL_SET_ERR_MSG_MOD(extack, "Can't set XDP while host is implementing GRO_HW/CSUM, disable GRO_HW/CSUM first");
return -EOPNOTSUPP;
}

@@ -2644,15 +2644,15 @@ static int virtnet_set_features(struct net_device *dev,
u64 offloads;
int err;

- if ((dev->features ^ features) & NETIF_F_LRO) {
+ if ((dev->features ^ features) & NETIF_F_GRO_HW) {
if (vi->xdp_enabled)
return -EBUSY;

- if (features & NETIF_F_LRO)
+ if (features & NETIF_F_GRO_HW)
offloads = vi->guest_offloads_capable;
else
offloads = vi->guest_offloads_capable &
- ~GUEST_OFFLOAD_LRO_MASK;
+ ~GUEST_OFFLOAD_GRO_HW_MASK;

err = virtnet_set_guest_offloads(vi, offloads);
if (err)
@@ -3128,9 +3128,9 @@ static int virtnet_probe(struct virtio_device *vdev)
dev->features |= NETIF_F_RXCSUM;
if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO4) ||
virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO6))
- dev->features |= NETIF_F_LRO;
+ dev->features |= NETIF_F_GRO_HW;
if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS))
- dev->hw_features |= NETIF_F_LRO;
+ dev->hw_features |= NETIF_F_GRO_HW;

dev->vlan_features = dev->features;

--
2.30.2