Subject: Re: [PATCH net-next v2] net: stmmac: Enable TSO on VLANs

From: Vadim Fedorenko <[email-masked]>
Date: Fri, 14 Jun 2024 11:43:00 +0100

On 14/06/2024 07:03, Furong Xu wrote:
> The TSO engine works well when the frames are not VLAN Tagged.
> But it will produce broken segments when frames are VLAN Tagged.
> 
> The first segment is all good, while the second segment to the
> last segment are broken, they lack of required VLAN tag.
> 
> An example here:
> ========
> // 1st segment of a VLAN Tagged TSO frame, nothing wrong.
> MacSrc > MacDst, ethertype 802.1Q (0x8100), length 1518: vlan 100, p 1, ethertype IPv4 (0x0800), HostA:42643 > HostB:5201: Flags [.], seq 1:1449
> 
> // 2nd to last segments of a VLAN Tagged TSO frame, VLAN tag is missing.
> MacSrc > MacDst, ethertype IPv4 (0x0800), length 1514: HostA:42643 > HostB:5201: Flags [.], seq 1449:2897
> MacSrc > MacDst, ethertype IPv4 (0x0800), length 1514: HostA:42643 > HostB:5201: Flags [.], seq 2897:4345
> MacSrc > MacDst, ethertype IPv4 (0x0800), length 1514: HostA:42643 > HostB:5201: Flags [.], seq 4345:5793
> MacSrc > MacDst, ethertype IPv4 (0x0800), length 1514: HostA:42643 > HostB:5201: Flags [P.], seq 5793:7241
> 
> // normal VLAN Tagged non-TSO frame, nothing wrong.
> MacSrc > MacDst, ethertype 802.1Q (0x8100), length 1022: vlan 100, p 1, ethertype IPv4 (0x0800), HostA:42643 > HostB:5201: Flags [P.], seq 7241:8193
> MacSrc > MacDst, ethertype 802.1Q (0x8100), length 70: vlan 100, p 1, ethertype IPv4 (0x0800), HostA:42643 > HostB:5201: Flags [F.], seq 8193
> ========
> 
> When transmitting VLAN Tagged TSO frames, never insert VLAN tag by HW,
> always insert VLAN tag to SKB payload, then TSO works well on VLANs for
> all MAC cores.
> 
> Tested on DWMAC CORE 5.10a, DWMAC CORE 5.20a and DWXGMAC CORE 3.20a
> 
> Signed-off-by: Furong Xu <[email-masked]>
> ---
>    Changes in v2:
>      - Use __vlan_hwaccel_push_inside() to insert vlan tag to the payload.
> ---
>   .../net/ethernet/stmicro/stmmac/stmmac_main.c | 27 ++++++++++---------
>   1 file changed, 14 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index bbedf2a8c60f..e8cbfada63ca 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -4233,18 +4233,27 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
>   {
>   	struct dma_desc *desc, *first, *mss_desc = NULL;
>   	struct stmmac_priv *priv = netdev_priv(dev);
> -	int nfrags = skb_shinfo(skb)->nr_frags;
> -	u32 queue = skb_get_queue_mapping(skb);
>   	unsigned int first_entry, tx_packets;
>   	struct stmmac_txq_stats *txq_stats;
> -	int tmp_pay_len = 0, first_tx;
> +	int tmp_pay_len = 0, first_tx, nfrags;
>   	struct stmmac_tx_queue *tx_q;
> -	bool has_vlan, set_ic;
> +	bool set_ic;
>   	u8 proto_hdr_len, hdr;
> -	u32 pay_len, mss;
> +	u32 pay_len, mss, queue;
>   	dma_addr_t des;
>   	int i;
>   

As there will be another iteration, could you please re-arrange
variables to keep reverse x-mas tree order?