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Message-ID: <31ea9c22-15e0-86db-a92d-76cee56fc738@pensando.io>
Date: Fri, 30 Aug 2019 14:44:24 -0700
From: Shannon Nelson <snelson@...sando.io>
To: Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc: netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: [PATCH v6 net-next 15/19] ionic: Add Tx and Rx handling
On 8/29/19 4:33 PM, Jakub Kicinski wrote:
> On Thu, 29 Aug 2019 11:27:16 -0700, Shannon Nelson wrote:
>> +static int ionic_tx_tso(struct ionic_queue *q, struct sk_buff *skb)
>> +{
>> + struct ionic_tx_stats *stats = q_to_tx_stats(q);
>> + struct ionic_desc_info *abort = q->head;
>> + struct device *dev = q->lif->ionic->dev;
>> + struct ionic_desc_info *rewind = abort;
>> + struct ionic_txq_sg_elem *elem;
>> + struct ionic_txq_desc *desc;
>> + unsigned int frag_left = 0;
>> + unsigned int offset = 0;
>> + unsigned int len_left;
>> + dma_addr_t desc_addr;
>> + unsigned int hdrlen;
>> + unsigned int nfrags;
>> + unsigned int seglen;
>> + u64 total_bytes = 0;
>> + u64 total_pkts = 0;
>> + unsigned int left;
>> + unsigned int len;
>> + unsigned int mss;
>> + skb_frag_t *frag;
>> + bool start, done;
>> + bool outer_csum;
>> + bool has_vlan;
>> + u16 desc_len;
>> + u8 desc_nsge;
>> + u16 vlan_tci;
>> + bool encap;
>> + int err;
>> +
>> + mss = skb_shinfo(skb)->gso_size;
>> + nfrags = skb_shinfo(skb)->nr_frags;
>> + len_left = skb->len - skb_headlen(skb);
>> + outer_csum = (skb_shinfo(skb)->gso_type & SKB_GSO_GRE_CSUM) ||
>> + (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL_CSUM);
>> + has_vlan = !!skb_vlan_tag_present(skb);
>> + vlan_tci = skb_vlan_tag_get(skb);
>> + encap = skb->encapsulation;
>> +
>> + /* Preload inner-most TCP csum field with IP pseudo hdr
>> + * calculated with IP length set to zero. HW will later
>> + * add in length to each TCP segment resulting from the TSO.
>> + */
>> +
>> + if (encap)
>> + err = ionic_tx_tcp_inner_pseudo_csum(skb);
>> + else
>> + err = ionic_tx_tcp_pseudo_csum(skb);
>> + if (err)
>> + return err;
>> +
>> + if (encap)
>> + hdrlen = skb_inner_transport_header(skb) - skb->data +
>> + inner_tcp_hdrlen(skb);
>> + else
>> + hdrlen = skb_transport_offset(skb) + tcp_hdrlen(skb);
>> +
>> + seglen = hdrlen + mss;
>> + left = skb_headlen(skb);
>> +
>> + desc = ionic_tx_tso_next(q, &elem);
>> + start = true;
>> +
>> + /* Chop skb->data up into desc segments */
>> +
>> + while (left > 0) {
>> + len = min(seglen, left);
>> + frag_left = seglen - len;
>> + desc_addr = ionic_tx_map_single(q, skb->data + offset, len);
>> + if (dma_mapping_error(dev, desc_addr))
>> + goto err_out_abort;
>> + desc_len = len;
>> + desc_nsge = 0;
>> + left -= len;
>> + offset += len;
>> + if (nfrags > 0 && frag_left > 0)
>> + continue;
>> + done = (nfrags == 0 && left == 0);
>> + ionic_tx_tso_post(q, desc, skb,
>> + desc_addr, desc_nsge, desc_len,
>> + hdrlen, mss,
>> + outer_csum,
>> + vlan_tci, has_vlan,
>> + start, done);
>> + total_pkts++;
>> + total_bytes += start ? len : len + hdrlen;
>> + desc = ionic_tx_tso_next(q, &elem);
>> + start = false;
>> + seglen = mss;
>> + }
>> +
>> + /* Chop skb frags into desc segments */
>> +
>> + for (frag = skb_shinfo(skb)->frags; len_left; frag++) {
>> + offset = 0;
>> + left = skb_frag_size(frag);
>> + len_left -= left;
>> + nfrags--;
>> + stats->frags++;
>> +
>> + while (left > 0) {
>> + if (frag_left > 0) {
>> + len = min(frag_left, left);
>> + frag_left -= len;
>> + elem->addr =
>> + cpu_to_le64(ionic_tx_map_frag(q, frag,
>> + offset, len));
>> + if (dma_mapping_error(dev, elem->addr))
>> + goto err_out_abort;
>> + elem->len = cpu_to_le16(len);
>> + elem++;
>> + desc_nsge++;
>> + left -= len;
>> + offset += len;
>> + if (nfrags > 0 && frag_left > 0)
>> + continue;
>> + done = (nfrags == 0 && left == 0);
>> + ionic_tx_tso_post(q, desc, skb, desc_addr,
>> + desc_nsge, desc_len,
>> + hdrlen, mss, outer_csum,
>> + vlan_tci, has_vlan,
>> + start, done);
>> + total_pkts++;
>> + total_bytes += start ? len : len + hdrlen;
>> + desc = ionic_tx_tso_next(q, &elem);
>> + start = false;
>> + } else {
>> + len = min(mss, left);
>> + frag_left = mss - len;
>> + desc_addr = ionic_tx_map_frag(q, frag,
>> + offset, len);
>> + if (dma_mapping_error(dev, desc_addr))
>> + goto err_out_abort;
>> + desc_len = len;
>> + desc_nsge = 0;
>> + left -= len;
>> + offset += len;
>> + if (nfrags > 0 && frag_left > 0)
>> + continue;
>> + done = (nfrags == 0 && left == 0);
>> + ionic_tx_tso_post(q, desc, skb, desc_addr,
>> + desc_nsge, desc_len,
>> + hdrlen, mss, outer_csum,
>> + vlan_tci, has_vlan,
>> + start, done);
>> + total_pkts++;
>> + total_bytes += start ? len : len + hdrlen;
>> + desc = ionic_tx_tso_next(q, &elem);
>> + start = false;
>> + }
>> + }
>> + }
>> +
>> + stats->pkts += total_pkts;
>> + stats->bytes += total_bytes;
>> + stats->tso++;
>> +
>> + return 0;
>> +
>> +err_out_abort:
>> + while (rewind->desc != q->head->desc) {
>> + ionic_tx_clean(q, rewind, NULL, NULL);
>> + rewind = rewind->next;
>> + }
>> + q->head = abort;
>> +
>> + return -ENOMEM;
>> +}
> There's definitely a function for helping drivers which can't do full
> TSO slice up the packet, but I can't find it now 😫😫
>
> Eric would definitely know.
>
> Did you have a look? Would it be useful here?
Yes, obviously this could use some work for clarity and supportability,
and I think for performance as well. But since it works, I've been
concentrating on getting other parts of the driver working before coming
back to this. If there are some tools that can help clean this up, I
would be interested to see them.
sln
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