netdev - Re: [PATCH v4 net-next 7/7] net: mvneta: add XDP

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Message-ID: <20191016182849.27d130db@cakuba.netronome.com>
Date:   Wed, 16 Oct 2019 18:28:48 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     netdev@...r.kernel.org, lorenzo.bianconi@...hat.com,
        davem@...emloft.net, thomas.petazzoni@...tlin.com,
        brouer@...hat.com, ilias.apalodimas@...aro.org,
        matteo.croce@...hat.com, mw@...ihalf.com
Subject: Re: [PATCH v4 net-next 7/7] net: mvneta: add XDP_TX support

On Wed, 16 Oct 2019 23:03:12 +0200, Lorenzo Bianconi wrote:
> Implement XDP_TX verdict and ndo_xdp_xmit net_device_ops function
> pointer
> 
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>

> +static int
> +mvneta_xdp_submit_frame(struct mvneta_port *pp, struct mvneta_tx_queue *txq,
> +			struct xdp_frame *xdpf, bool dma_map)
> +{
> +	struct mvneta_tx_desc *tx_desc;
> +	struct mvneta_tx_buf *buf;
> +	dma_addr_t dma_addr;
> +
> +	if (txq->count >= txq->tx_stop_threshold)
> +		return MVNETA_XDP_DROPPED;
> +
> +	tx_desc = mvneta_txq_next_desc_get(txq);
> +
> +	buf = &txq->buf[txq->txq_put_index];
> +	if (dma_map) {
> +		/* ndo_xdp_xmit */
> +		dma_addr = dma_map_single(pp->dev->dev.parent, xdpf->data,
> +					  xdpf->len, DMA_TO_DEVICE);
> +		if (dma_mapping_error(pp->dev->dev.parent, dma_addr)) {
> +			mvneta_txq_desc_put(txq);
> +			return MVNETA_XDP_DROPPED;
> +		}
> +		buf->type = MVNETA_TYPE_XDP_NDO;
> +	} else {
> +		struct page *page = virt_to_page(xdpf->data);
> +
> +		dma_addr = page_pool_get_dma_addr(page) +
> +			   xdpf->headroom + sizeof(*xdpf);

nit:

 sizeof(*xdpf) + xdpf->headroom

order would be slightly preferable since it matches field ordering in
memory.

> +		dma_sync_single_for_device(pp->dev->dev.parent, dma_addr,
> +					   xdpf->len, DMA_BIDIRECTIONAL);
> +		buf->type = MVNETA_TYPE_XDP_TX;
> +	}
> +	buf->xdpf = xdpf;
> +
> +	tx_desc->command = MVNETA_TXD_FLZ_DESC;
> +	tx_desc->buf_phys_addr = dma_addr;
> +	tx_desc->data_size = xdpf->len;
> +
> +	mvneta_update_stats(pp, 1, xdpf->len, true);
> +	mvneta_txq_inc_put(txq);
> +	txq->pending++;
> +	txq->count++;
> +
> +	return MVNETA_XDP_TX;
> +}