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

[Jens Freimann <jfreimann@redhat.com>]

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

This can be triggered by running testpmd e.g. with --max-pkt-len=2000.
It will fail with "Ethdev port_id=0 requested Rx offloads 0x800 doesn't
match Rx offloads capabilities 0x20d in rte_eth_dev_configure()"

To fix this there are two cases to consider:

1. VIRTIO_NET_F_MTU is negotiated. Then we need to check if the
   requested max. packet length fits into the MTU. If yes we set the
   offload flag.
2. VIRTIO_NET_F_MTU is not negotiated. We can set the offload flag.

Signed-off-by: Jens Freimann <jfreimann@redhat.com>
---
 drivers/net/virtio/virtio_ethdev.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
index 7c4c1df00..e0d6542d4 100644
--- a/drivers/net/virtio/virtio_ethdev.c
+++ b/drivers/net/virtio/virtio_ethdev.c
@@ -2351,6 +2351,17 @@ 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;
+		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)
+			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