[dpdk-stable] [PATCH v3] net/virtio: set offload flag for jumbo frames

[Jens Freimann]

Port configuration fails because offload flags don't match the expected
value when max-pkt-len is set to a value that should enable receive port
offloading but doesn't.

There are two cases to consider:

1. VIRTIO_NET_F_MTU is set. Then we need to check if the requested
   max-pkt-len fits into the MTU plus header. If yes we set the
   offload flag.
2. VIRTIO_NET_F_MTU is not set. We can set the offload flag.

Fixes: a4996bd89c42 ("ethdev: new Rx/Tx offloads API")
Cc: stable at dpdk.org

Signed-off-by: Jens Freimann <jfreimann at redhat.com>
---
v2->v3:
 * remove unnecessary brackets (Maxime)
 * fix commit message (David)

v1->v2:
 * include virtnet hdr, ethernet header, vlan tag when comparing against
   max-rx-pkt-len (Maxime)

 drivers/net/virtio/virtio_ethdev.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
index 7c4c1df00..f39d4e630 100644
--- a/drivers/net/virtio/virtio_ethdev.c
+++ b/drivers/net/virtio/virtio_ethdev.c
@@ -2351,6 +2351,20 @@ virtio_dev_info_get(struct rte_eth_dev *dev, struct rte_eth_dev_info *dev_info)
 	if ((host_features & tso_mask) == tso_mask)
 		dev_info->rx_offload_capa |= DEV_RX_OFFLOAD_TCP_LRO;
 
+	if (host_features & (1ULL << VIRTIO_NET_F_MTU)) {
+		struct virtio_net_config config;
+		uint32_t ether_hdr_len = ETHER_HDR_LEN + VLAN_TAG_LEN +
+			hw->vtnet_hdr_size;
+		vtpci_read_dev_config(hw,
+				offsetof(struct virtio_net_config, mtu),
+				&config.mtu, sizeof(config.mtu));
+		if (dev->data->dev_conf.rxmode.max_rx_pkt_len <=
+				config.mtu + ether_hdr_len)
+			dev_info->rx_offload_capa |= DEV_RX_OFFLOAD_JUMBO_FRAME;
+	} else {
+		dev_info->rx_offload_capa |= DEV_RX_OFFLOAD_JUMBO_FRAME;
+	}
+
 	dev_info->tx_offload_capa = DEV_TX_OFFLOAD_MULTI_SEGS |
 				    DEV_TX_OFFLOAD_VLAN_INSERT;
 	if (host_features & (1ULL << VIRTIO_NET_F_CSUM)) {
-- 
2.17.2