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Date: Fri, 30 Oct 2020 11:49:44 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Edward Cree <ecree@...arflare.com>
Cc: linux-net-drivers@...arflare.com, Jakub Kicinski <kuba@...nel.org>,
David Miller <davem@...emloft.net>,
Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 2/4] sfc: implement encap TSO on EF100
On Wed, Oct 28, 2020 at 9:39 PM Edward Cree <ecree@...arflare.com> wrote:
>
> The NIC only needs to know where the headers it has to edit (TCP and
> inner and outer IPv4) are, which fits GSO_PARTIAL nicely.
> It also supports non-PARTIAL offload of UDP tunnels, again just
> needing to be told the outer transport offset so that it can edit
> the UDP length field.
> (It's not clear to me whether the stack will ever use the non-PARTIAL
> version with the netdev feature flags we're setting here.)
>
> Signed-off-by: Edward Cree <ecree@...arflare.com>
> ---
> drivers/net/ethernet/sfc/ef100_nic.c | 13 ++++++--
> drivers/net/ethernet/sfc/ef100_tx.c | 45 ++++++++++++++++------------
> 2 files changed, 37 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/net/ethernet/sfc/ef100_nic.c b/drivers/net/ethernet/sfc/ef100_nic.c
> index 3148fe770356..bf92cdc60cda 100644
> --- a/drivers/net/ethernet/sfc/ef100_nic.c
> +++ b/drivers/net/ethernet/sfc/ef100_nic.c
> @@ -182,8 +182,16 @@ static int efx_ef100_init_datapath_caps(struct efx_nic *efx)
> if (rc)
> return rc;
>
> - if (efx_ef100_has_cap(nic_data->datapath_caps2, TX_TSO_V3))
> - efx->net_dev->features |= NETIF_F_TSO | NETIF_F_TSO6;
> + if (efx_ef100_has_cap(nic_data->datapath_caps2, TX_TSO_V3)) {
> + struct net_device *net_dev = efx->net_dev;
> + netdev_features_t tso = NETIF_F_TSO | NETIF_F_TSO6 | NETIF_F_GSO_PARTIAL |
> + NETIF_F_GSO_UDP_TUNNEL | NETIF_F_GSO_UDP_TUNNEL_CSUM;
> +
> + net_dev->features |= tso;
> + net_dev->hw_features |= tso;
> + net_dev->hw_enc_features |= tso;
> + net_dev->gso_partial_features |= NETIF_F_GSO_UDP_TUNNEL | NETIF_F_GSO_UDP_TUNNEL_CSUM;
> + }
> efx->num_mac_stats = MCDI_WORD(outbuf,
> GET_CAPABILITIES_V4_OUT_MAC_STATS_NUM_STATS);
> netif_dbg(efx, probe, efx->net_dev,
> @@ -1101,6 +1109,7 @@ static int ef100_probe_main(struct efx_nic *efx)
> nic_data->efx = efx;
> net_dev->features |= efx->type->offload_features;
> net_dev->hw_features |= efx->type->offload_features;
> + net_dev->hw_enc_features |= efx->type->offload_features;
>
> /* Populate design-parameter defaults */
> nic_data->tso_max_hdr_len = ESE_EF100_DP_GZ_TSO_MAX_HDR_LEN_DEFAULT;
> diff --git a/drivers/net/ethernet/sfc/ef100_tx.c b/drivers/net/ethernet/sfc/ef100_tx.c
> index a90e5a9d2a37..d267b12bdaa0 100644
> --- a/drivers/net/ethernet/sfc/ef100_tx.c
> +++ b/drivers/net/ethernet/sfc/ef100_tx.c
> @@ -54,8 +54,6 @@ static bool ef100_tx_can_tso(struct efx_tx_queue *tx_queue, struct sk_buff *skb)
> struct efx_nic *efx = tx_queue->efx;
> struct ef100_nic_data *nic_data;
> struct efx_tx_buffer *buffer;
> - struct tcphdr *tcphdr;
> - struct iphdr *iphdr;
> size_t header_len;
> u32 mss;
>
> @@ -98,20 +96,6 @@ static bool ef100_tx_can_tso(struct efx_tx_queue *tx_queue, struct sk_buff *skb)
> buffer->unmap_len = 0;
> buffer->skb = skb;
> ++tx_queue->insert_count;
> -
> - /* Adjust the TCP checksum to exclude the total length, since we set
> - * ED_INNER_IP_LEN in the descriptor.
> - */
> - tcphdr = tcp_hdr(skb);
> - if (skb_is_gso_v6(skb)) {
> - tcphdr->check = ~csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
> - &ipv6_hdr(skb)->daddr,
> - 0, IPPROTO_TCP, 0);
> - } else {
> - iphdr = ip_hdr(skb);
> - tcphdr->check = ~csum_tcpudp_magic(iphdr->saddr, iphdr->daddr,
> - 0, IPPROTO_TCP, 0);
> - }
> return true;
> }
>
> @@ -209,17 +193,35 @@ static void ef100_make_tso_desc(struct efx_nic *efx,
> ESE_GZ_TX_DESC_IP4_ID_INC_MOD16;
> u16 vlan_enable = efx->net_dev->features & NETIF_F_HW_VLAN_CTAG_TX ?
> skb_vlan_tag_present(skb) : 0;
> + bool gso_partial = skb_shinfo(skb)->gso_type & SKB_GSO_PARTIAL;
> unsigned int len, ip_offset, tcp_offset, payload_segs;
> + unsigned int outer_ip_offset, outer_l4_offset;
> u16 vlan_tci = skb_vlan_tag_get(skb);
> u32 mss = skb_shinfo(skb)->gso_size;
> + bool encap = skb->encapsulation;
> + struct tcphdr *tcp;
> + u32 paylen;
>
> len = skb->len - buffer->len;
> /* We use 1 for the TSO descriptor and 1 for the header */
> payload_segs = segment_count - 2;
> - ip_offset = skb_network_offset(skb);
> - tcp_offset = skb_transport_offset(skb);
> + if (encap) {
> + outer_ip_offset = skb_network_offset(skb);
> + outer_l4_offset = skb_transport_offset(skb);
> + ip_offset = skb_inner_network_offset(skb);
> + tcp_offset = skb_inner_transport_offset(skb);
> + } else {
> + ip_offset = skb_network_offset(skb);
> + tcp_offset = skb_transport_offset(skb);
> + outer_ip_offset = outer_l4_offset = 0;
> + }
> +
> + /* subtract TCP payload length from inner checksum */
> + tcp = (void *)skb->data + tcp_offset;
> + paylen = skb->len - tcp_offset;
> + csum_replace_by_diff(&tcp->check, (__force __wsum)htonl(paylen));
>
> - EFX_POPULATE_OWORD_13(*txd,
> + EFX_POPULATE_OWORD_17(*txd,
> ESF_GZ_TX_DESC_TYPE, ESE_GZ_TX_DESC_TYPE_TSO,
> ESF_GZ_TX_TSO_MSS, mss,
> ESF_GZ_TX_TSO_HDR_NUM_SEGS, 1,
> @@ -231,6 +233,11 @@ static void ef100_make_tso_desc(struct efx_nic *efx,
> ESF_GZ_TX_TSO_INNER_L4_OFF_W, tcp_offset >> 1,
> ESF_GZ_TX_TSO_ED_INNER_IP4_ID, mangleid,
> ESF_GZ_TX_TSO_ED_INNER_IP_LEN, 1,
> + ESF_GZ_TX_TSO_OUTER_L3_OFF_W, outer_ip_offset >> 1,
> + ESF_GZ_TX_TSO_OUTER_L4_OFF_W, outer_l4_offset >> 1,
> + ESF_GZ_TX_TSO_ED_OUTER_UDP_LEN, encap && !gso_partial,
This is a boolean field to signal whether the NIC needs to fix up the
udp length field ?
Which in the case of GSO_PARTIAL has already been resolved by the gso
layer (in __skb_udp_tunnel_segment).
Just curious, is this ever expected to be true? Not based on current
advertised features, right?
> + ESF_GZ_TX_TSO_ED_OUTER_IP4_ID, encap ? mangleid :
> + ESE_GZ_TX_DESC_IP4_ID_NO_OP,
> ESF_GZ_TX_TSO_VLAN_INSERT_EN, vlan_enable,
> ESF_GZ_TX_TSO_VLAN_INSERT_TCI, vlan_tci
> );
>
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