Re: [PATCH] net/virtio: include ipv4 cksum to support cksum offload capability

[Maxime Coquelin <maxime.coquelin@redhat.com>]

Hi Harold,

On 1/7/22 12:53, Harold Huang wrote:
> Device cksum offload capability usually include ipv4 cksum, tcp and udp
> cksum offload capability. The application such as OVS usually negotiate
> with the drive like this to enable cksum offload.
> 
> Signed-off-by: Harold Huang <baymaxhuang@gmail.com>
> ---
>   drivers/net/virtio/virtio_ethdev.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
> index c2588369b2..65b03bf0e4 100644
> --- a/drivers/net/virtio/virtio_ethdev.c
> +++ b/drivers/net/virtio/virtio_ethdev.c
> @@ -3041,6 +3041,7 @@ virtio_dev_info_get(struct rte_eth_dev *dev, struct rte_eth_dev_info *dev_info)
>   		dev_info->rx_offload_capa |= RTE_ETH_RX_OFFLOAD_SCATTER;
>   	if (host_features & (1ULL << VIRTIO_NET_F_GUEST_CSUM)) {
>   		dev_info->rx_offload_capa |=
> +			RTE_ETH_RX_OFFLOAD_IPV4_CKSUM |
>   			RTE_ETH_RX_OFFLOAD_TCP_CKSUM |
>   			RTE_ETH_RX_OFFLOAD_UDP_CKSUM;
>   	}
> @@ -3055,6 +3056,7 @@ virtio_dev_info_get(struct rte_eth_dev *dev, struct rte_eth_dev_info *dev_info)
>   				    RTE_ETH_TX_OFFLOAD_VLAN_INSERT;
>   	if (host_features & (1ULL << VIRTIO_NET_F_CSUM)) {
>   		dev_info->tx_offload_capa |=
> +			RTE_ETH_TX_OFFLOAD_IPV4_CKSUM |
>   			RTE_ETH_TX_OFFLOAD_UDP_CKSUM |
>   			RTE_ETH_TX_OFFLOAD_TCP_CKSUM;
>   	}

I'm not sure to understand why this is needed, as Vhost lib will always
ensure the IP csum has been calculated. Could you please elaborate?

Thanks,
Maxime