On Fri, 9 Apr 2021 09:43:50 -0700 Tony Nguyen wrote:
> From: Andre Guedes <andre.gue...@intel.com>
>
> Add support for receiving packets via AF_XDP zero-copy mechanism.
>
> Add a new flag to 'enum igc_ring_flags_t' to indicate the ring has
> AF_XDP zero-copy enabled so proper ring setup is carried out during ring
> configuration in igc_configure_rx_ring().
>
> RX buffers can now be allocated via the shared pages mechanism (default
> behavior of the driver) or via xsk pool (when AF_XDP zero-copy is
> enabled) so a union is added to the 'struct igc_rx_buffer' to cover both
> cases.
>
> When AF_XDP zero-copy is enabled, rx buffers are allocated from the xsk
> pool using the new helper igc_alloc_rx_buffers_zc() which is the
> counterpart of igc_alloc_rx_buffers().
>
> Likewise other Intel drivers that support AF_XDP zero-copy, in igc we
> have a dedicated path for cleaning up rx irqs when zero-copy is enabled.
> This avoids adding too many checks within igc_clean_rx_irq(), resulting
> in a more readable and efficient code since this function is called from
> the hot-path of the driver.
> +static struct sk_buff *igc_construct_skb_zc(struct igc_ring *ring,
> + struct xdp_buff *xdp)
> +{
> + unsigned int metasize = xdp->data - xdp->data_meta;
> + unsigned int datasize = xdp->data_end - xdp->data;
> + struct sk_buff *skb;
> +
> + skb = __napi_alloc_skb(&ring->q_vector->napi,
> + xdp->data_end - xdp->data_hard_start,
> + GFP_ATOMIC | __GFP_NOWARN);
> + if (unlikely(!skb))
> + return NULL;
> +
> + skb_reserve(skb, xdp->data - xdp->data_hard_start);
> + memcpy(__skb_put(skb, datasize), xdp->data, datasize);
> + if (metasize)
> + skb_metadata_set(skb, metasize);
But you haven't actually copied the matadata into the skb,
the metadata is before xdp->data, right?
> + return skb;
> +}
> +static int igc_xdp_enable_pool(struct igc_adapter *adapter,
> + struct xsk_buff_pool *pool, u16 queue_id)
> +{
> + struct net_device *ndev = adapter->netdev;
> + struct device *dev = &adapter->pdev->dev;
> + struct igc_ring *rx_ring;
> + struct napi_struct *napi;
> + bool needs_reset;
> + u32 frame_size;
> + int err;
> +
> + if (queue_id >= adapter->num_rx_queues)
> + return -EINVAL;
> +
> + frame_size = xsk_pool_get_rx_frame_size(pool);
> + if (frame_size < ETH_FRAME_LEN + VLAN_HLEN * 2) {
> + /* When XDP is enabled, the driver doesn't support frames that
> + * span over multiple buffers. To avoid that, we check if xsk
> + * frame size is big enough to fit the max ethernet frame size
> + * + vlan double tagging.
> + */
> + return -EOPNOTSUPP;
> + }
> +
> + err = xsk_pool_dma_map(pool, dev, IGC_RX_DMA_ATTR);
> + if (err) {
> + netdev_err(ndev, "Failed to map xsk pool\n");
> + return err;
> + }
> +
> + needs_reset = netif_running(adapter->netdev) &&
> igc_xdp_is_enabled(adapter);
> +
> + rx_ring = adapter->rx_ring[queue_id];
> + napi = &rx_ring->q_vector->napi;
> +
> + if (needs_reset) {
> + igc_disable_rx_ring(rx_ring);
> + napi_disable(napi);
> + }
> +
> + set_bit(IGC_RING_FLAG_AF_XDP_ZC, &rx_ring->flags);
> +
> + if (needs_reset) {
> + napi_enable(napi);
> + igc_enable_rx_ring(rx_ring);
> +
> + err = igc_xsk_wakeup(ndev, queue_id, XDP_WAKEUP_RX);
> + if (err)
> + return err;
No need for an unwind path here?
Does something call XDP_SETUP_XSK_POOL(NULL) on failure automagically?
> + }
> +
> + return 0;
> +}
