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Date:   Wed, 20 Jul 2022 09:57:17 +0200
From:   Lorenzo Bianconi <lorenzo@...nel.org>
To:     "Neftin, Sasha" <sasha.neftin@...el.com>
Cc:     netdev@...r.kernel.org, intel-wired-lan@...ts.osuosl.org,
        jesse.brandeburg@...el.com, jbrouer@...hat.com,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        davem@...emloft.net, magnus.karlsson@...el.com,
        "Fuxbrumer, Devora" <devora.fuxbrumer@...el.com>,
        "naamax.meir" <naamax.meir@...ux.intel.com>,
        "Edri, Michael" <michael.edri@...el.com>,
        "Gomes, Vinicius" <vinicius.gomes@...el.com>
Subject: Re: [Intel-wired-lan] [PATCH net-next] igc: add xdp frags support to
 ndo_xdp_xmit

> On 7/6/2022 10:54, Lorenzo Bianconi wrote:
> > Add the capability to map non-linear xdp frames in XDP_TX and
> > ndo_xdp_xmit callback.
> > 
> > Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> > ---
> > Please note this patch is only compiled tested since I do not have
> > access to a igc NIC
> > ---
> >   drivers/net/ethernet/intel/igc/igc_main.c | 128 ++++++++++++++--------
> >   1 file changed, 83 insertions(+), 45 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> > index ae17af44fe02..71657d03da03 100644
> > --- a/drivers/net/ethernet/intel/igc/igc_main.c
> > +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> > @@ -2129,65 +2129,102 @@ static bool igc_alloc_rx_buffers_zc(struct igc_ring *ring, u16 count)
> >   	return ok;
> >   }
> > -static int igc_xdp_init_tx_buffer(struct igc_tx_buffer *buffer,
> > -				  struct xdp_frame *xdpf,
> > -				  struct igc_ring *ring)
> > -{
> > -	dma_addr_t dma;
> > -
> > -	dma = dma_map_single(ring->dev, xdpf->data, xdpf->len, DMA_TO_DEVICE);
> > -	if (dma_mapping_error(ring->dev, dma)) {
> > -		netdev_err_once(ring->netdev, "Failed to map DMA for TX\n");
> > -		return -ENOMEM;
> > -	}
> > -
> > -	buffer->type = IGC_TX_BUFFER_TYPE_XDP;
> > -	buffer->xdpf = xdpf;
> > -	buffer->protocol = 0;
> > -	buffer->bytecount = xdpf->len;
> > -	buffer->gso_segs = 1;
> > -	buffer->time_stamp = jiffies;
> > -	dma_unmap_len_set(buffer, len, xdpf->len);
> > -	dma_unmap_addr_set(buffer, dma, dma);
> > -	return 0;
> > -}
> > -
> >   /* This function requires __netif_tx_lock is held by the caller. */
> >   static int igc_xdp_init_tx_descriptor(struct igc_ring *ring,
> >   				      struct xdp_frame *xdpf)
> >   {
> > -	struct igc_tx_buffer *buffer;
> > -	union igc_adv_tx_desc *desc;
> > -	u32 cmd_type, olinfo_status;
> > -	int err;
> > +	struct skb_shared_info *sinfo = xdp_get_shared_info_from_frame(xdpf);
> > +	u8 nr_frags = unlikely(xdp_frame_has_frags(xdpf)) ? sinfo->nr_frags : 0;
> > +	u16 count, index = ring->next_to_use;
> > +	struct igc_tx_buffer *head = &ring->tx_buffer_info[index];
> > +	struct igc_tx_buffer *buffer = head;
> > +	union igc_adv_tx_desc *desc = IGC_TX_DESC(ring, index);
> > +	u32 olinfo_status, len = xdpf->len, cmd_type;
> > +	void *data = xdpf->data;
> > +	u16 i;
> > -	if (!igc_desc_unused(ring))
> > -		return -EBUSY;
> > +	count = TXD_USE_COUNT(len);
> > +	for (i = 0; i < nr_frags; i++)
> > +		count += TXD_USE_COUNT(skb_frag_size(&sinfo->frags[i]));
> > -	buffer = &ring->tx_buffer_info[ring->next_to_use];
> > -	err = igc_xdp_init_tx_buffer(buffer, xdpf, ring);
> > -	if (err)
> > -		return err;
> > +	if (igc_maybe_stop_tx(ring, count + 3)) {
> > +		/* this is a hard error */
> > +		return -EBUSY;
> > +	}
> > -	cmd_type = IGC_ADVTXD_DTYP_DATA | IGC_ADVTXD_DCMD_DEXT |
> > -		   IGC_ADVTXD_DCMD_IFCS | IGC_TXD_DCMD |
> > -		   buffer->bytecount;
> > -	olinfo_status = buffer->bytecount << IGC_ADVTXD_PAYLEN_SHIFT;
> > +	i = 0;
> > +	head->bytecount = xdp_get_frame_len(xdpf);
> > +	head->type = IGC_TX_BUFFER_TYPE_XDP;
> > +	head->gso_segs = 1;
> > +	head->xdpf = xdpf;
> > -	desc = IGC_TX_DESC(ring, ring->next_to_use);
> > -	desc->read.cmd_type_len = cpu_to_le32(cmd_type);
> > +	olinfo_status = head->bytecount << IGC_ADVTXD_PAYLEN_SHIFT;
> >   	desc->read.olinfo_status = cpu_to_le32(olinfo_status);
> > -	desc->read.buffer_addr = cpu_to_le64(dma_unmap_addr(buffer, dma));
> > -	netdev_tx_sent_queue(txring_txq(ring), buffer->bytecount);
> > +	for (;;) {
> > +		dma_addr_t dma;
> > -	buffer->next_to_watch = desc;
> > +		dma = dma_map_single(ring->dev, data, len, DMA_TO_DEVICE);
> > +		if (dma_mapping_error(ring->dev, dma)) {
> > +			netdev_err_once(ring->netdev,
> > +					"Failed to map DMA for TX\n");
> > +			goto unmap;
> > +		}
> > -	ring->next_to_use++;
> > -	if (ring->next_to_use == ring->count)
> > -		ring->next_to_use = 0;
> > +		dma_unmap_len_set(buffer, len, len);
> > +		dma_unmap_addr_set(buffer, dma, dma);
> > +
> > +		cmd_type = IGC_ADVTXD_DTYP_DATA | IGC_ADVTXD_DCMD_DEXT |
> > +			   IGC_ADVTXD_DCMD_IFCS | len;
> > +
> > +		desc->read.cmd_type_len = cpu_to_le32(cmd_type);
> > +		desc->read.buffer_addr = cpu_to_le64(dma);
> > +
> > +		buffer->protocol = 0;
> > +
> > +		if (++index == ring->count)
> > +			index = 0;
> > +
> > +		if (i == nr_frags)
> > +			break;
> > +
> > +		buffer = &ring->tx_buffer_info[index];
> > +		desc = IGC_TX_DESC(ring, index);
> > +		desc->read.olinfo_status = 0;
> > +
> > +		data = skb_frag_address(&sinfo->frags[i]);
> > +		len = skb_frag_size(&sinfo->frags[i]);
> > +		i++;
> > +	}
> > +	desc->read.cmd_type_len |= cpu_to_le32(IGC_TXD_DCMD);
> > +
> > +	netdev_tx_sent_queue(txring_txq(ring), head->bytecount);
> > +	/* set the timestamp */
> > +	head->time_stamp = jiffies;
> > +	/* set next_to_watch value indicating a packet is present */
> > +	head->next_to_watch = desc;
> > +	ring->next_to_use = index;
> >   	return 0;
> > +
> > +unmap:
> > +	for (;;) {
> > +		buffer = &ring->tx_buffer_info[index];
> > +		if (dma_unmap_len(buffer, len))
> > +			dma_unmap_page(ring->dev,
> > +				       dma_unmap_addr(buffer, dma),
> > +				       dma_unmap_len(buffer, len),
> > +				       DMA_TO_DEVICE);
> > +		dma_unmap_len_set(buffer, len, 0);
> > +		if (buffer == head)
> > +			break;
> > +
> > +		if (!index)
> > +			index += ring->count;
> > +		index--;
> > +	}
> > +
> > +	return -ENOMEM;
> >   }
> >   static struct igc_ring *igc_xdp_get_tx_ring(struct igc_adapter *adapter,
> > @@ -2369,6 +2406,7 @@ static int igc_clean_rx_irq(struct igc_q_vector *q_vector, const int budget)
> >   			xdp_prepare_buff(&xdp, pktbuf - igc_rx_offset(rx_ring),
> >   					 igc_rx_offset(rx_ring) + pkt_offset,
> >   					 size, true);
> > +			xdp_buff_clear_frags_flag(&xdp);
> >   			skb = igc_xdp_run_prog(adapter, &xdp);
> >   		}
> Hello Lorenzo,
> Could you provide test hints (step by step) on how to test it?
> Sasha

Hi Sasha,

I guess you can just run the script I shared, does it work?

Regards,
Lorenzo

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