> -----Original Message-----
> From: Maxime Coquelin <maxime.coque...@redhat.com>
> Sent: 2022年5月5日 18:27
> To: dev@dpdk.org; jasow...@redhat.com; Xia, Chenbo
> <chenbo....@intel.com>; david.march...@redhat.com;
> olivier.m...@6wind.com
> Cc: sta...@dpdk.org; Maxime Coquelin <maxime.coque...@redhat.com>
> Subject: [PATCH 6/6] net/vhost: perform SW checksum in Tx path
>
> Virtio specification supports guest checksum offloading for L4, which is
> enabled with VIRTIO_NET_F_GUEST_CSUM feature negotiation. However,
> the Vhost PMD does not advertise Tx checksum offload capabilities.
>
> Advertising these offload capabilities at the ethdev level is not enough,
> because we could still end-up with the application enabling these offloads
> while the guest not negotiating it.
>
> This patch advertizes the Tx checksum offload capabilities, and introduces a
> compatibility layer to cover the case VIRTIO_NET_F_GUEST_CSUM has not
> been negotiated but the application does configure the Tx checksum
> offloads. This function performs the L4 Tx checksum in SW for UDP and TCP.
> Compared to Rx SW checksum, the Tx SW checksum function needs to
> compute the pseudo-header checksum, as we cannot knwo whether it was
> done before.
>
> This patch does not advertize SCTP checksum offloading capability for now,
> but it could be handled later if the need arises.
In virtio_enqueue_offload(), if RTE_MBUF_F_TX_IP_CKSUM is set, we will
performs the L3 Tx checksum, why do not we advertise IPV4 checksum offloading
capability?
Will we advertise it later?
>
> Reported-by: Jason Wang <jasow...@redhat.com>
> Signed-off-by: Maxime Coquelin <maxime.coque...@redhat.com>
> ---
> drivers/net/vhost/rte_eth_vhost.c | 62
> +++++++++++++++++++++++++++++++
> 1 file changed, 62 insertions(+)
>
> diff --git a/drivers/net/vhost/rte_eth_vhost.c
> b/drivers/net/vhost/rte_eth_vhost.c
> index d5303f7368..52a802de05 100644
> --- a/drivers/net/vhost/rte_eth_vhost.c
> +++ b/drivers/net/vhost/rte_eth_vhost.c
> @@ -114,6 +114,7 @@ struct pmd_internal {
> rte_atomic32_t started;
> bool vlan_strip;
> bool rx_sw_csum;
> + bool tx_sw_csum;
> };
>
> struct internal_list {
> @@ -370,8 +371,10 @@ vhost_dev_csum_configure(struct rte_eth_dev
> *eth_dev) {
> struct pmd_internal *internal = eth_dev->data->dev_private;
> const struct rte_eth_rxmode *rxmode = ð_dev->data-
> >dev_conf.rxmode;
> + const struct rte_eth_txmode *txmode = ð_dev->data-
> >dev_conf.txmode;
>
> internal->rx_sw_csum = false;
> + internal->tx_sw_csum = false;
>
> /* SW checksum is not compatible with legacy mode */
> if (!(internal->flags &
> RTE_VHOST_USER_NET_COMPLIANT_OL_FLAGS))
> @@ -384,6 +387,56 @@ vhost_dev_csum_configure(struct rte_eth_dev
> *eth_dev)
> internal->rx_sw_csum = true;
> }
> }
> +
> + if (!(internal->features & (1ULL << VIRTIO_NET_F_GUEST_CSUM))) {
> + if (txmode->offloads &
> + (RTE_ETH_TX_OFFLOAD_UDP_CKSUM |
> RTE_ETH_TX_OFFLOAD_TCP_CKSUM)) {
> + VHOST_LOG(NOTICE, "Tx csum will be done in SW,
> may impact performance.");
> + internal->tx_sw_csum = true;
> + }
> + }
> +}
> +
> +static void
> +vhost_dev_tx_sw_csum(struct rte_mbuf *mbuf) {
> + uint32_t hdr_len;
> + uint16_t csum = 0, csum_offset;
> +
> + switch (mbuf->ol_flags & RTE_MBUF_F_TX_L4_MASK) {
> + case RTE_MBUF_F_TX_L4_NO_CKSUM:
> + return;
> + case RTE_MBUF_F_TX_TCP_CKSUM:
> + csum_offset = offsetof(struct rte_tcp_hdr, cksum);
> + break;
> + case RTE_MBUF_F_TX_UDP_CKSUM:
> + csum_offset = offsetof(struct rte_udp_hdr, dgram_cksum);
> + break;
> + default:
> + /* Unsupported packet type. */
> + return;
> + }
> +
> + hdr_len = mbuf->l2_len + mbuf->l3_len;
> + csum_offset += hdr_len;
> +
> + /* Prepare the pseudo-header checksum */
> + if (rte_net_intel_cksum_prepare(mbuf) < 0)
> + return;
> +
> + if (rte_raw_cksum_mbuf(mbuf, hdr_len,
> rte_pktmbuf_pkt_len(mbuf) - hdr_len, &csum) < 0)
> + return;
> +
> + csum = ~csum;
> + /* See RFC768 */
> + if (unlikely((mbuf->packet_type & RTE_PTYPE_L4_UDP) && csum ==
> 0))
> + csum = 0xffff;
> +
> + if (rte_pktmbuf_data_len(mbuf) >= csum_offset + 1)
> + *rte_pktmbuf_mtod_offset(mbuf, uint16_t *, csum_offset)
> = csum;
> +
> + mbuf->ol_flags &= ~RTE_MBUF_F_TX_L4_MASK;
> + mbuf->ol_flags |= RTE_MBUF_F_TX_L4_NO_CKSUM;
> }
>
> static void
> @@ -513,6 +566,10 @@ eth_vhost_tx(void *q, struct rte_mbuf **bufs,
> uint16_t nb_bufs)
> }
> }
>
> + if (r->internal->tx_sw_csum)
> + vhost_dev_tx_sw_csum(m);
> +
> +
> bufs[nb_send] = m;
> ++nb_send;
> }
> @@ -1359,6 +1416,11 @@ eth_dev_info(struct rte_eth_dev *dev,
>
> dev_info->tx_offload_capa = RTE_ETH_TX_OFFLOAD_MULTI_SEGS |
> RTE_ETH_TX_OFFLOAD_VLAN_INSERT;
> + if (internal->flags & RTE_VHOST_USER_NET_COMPLIANT_OL_FLAGS)
> {
> + dev_info->tx_offload_capa |=
> RTE_ETH_TX_OFFLOAD_UDP_CKSUM |
> + RTE_ETH_TX_OFFLOAD_TCP_CKSUM;
> + }
> +
> dev_info->rx_offload_capa = RTE_ETH_RX_OFFLOAD_VLAN_STRIP;
> if (internal->flags & RTE_VHOST_USER_NET_COMPLIANT_OL_FLAGS)
> {
> dev_info->rx_offload_capa |=
> RTE_ETH_RX_OFFLOAD_UDP_CKSUM |
> --
> 2.35.1
