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Date: Sun, 6 Dec 2020 21:22:30 +0100
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: akiyano@...zon.com
Cc: davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
dwmw@...zon.com, zorik@...zon.com, matua@...zon.com,
saeedb@...zon.com, msw@...zon.com, aliguori@...zon.com,
nafea@...zon.com, gtzalik@...zon.com, netanel@...zon.com,
alisaidi@...zon.com, benh@...zon.com, ndagan@...zon.com,
shayagr@...zon.com, sameehj@...zon.com
Subject: Re: [PATCH V4 net-next 9/9] net: ena: introduce ndo_xdp_xmit()
function for XDP_REDIRECT
On Fri, Dec 04, 2020 at 02:11:15PM +0200, akiyano@...zon.com wrote:
> From: Arthur Kiyanovski <akiyano@...zon.com>
>
> This patch implements the ndo_xdp_xmit() net_device function which is
> called when a packet is redirected to this driver using an
> XDP_REDIRECT directive.
>
> The function receives an array of xdp frames that it needs to xmit.
> The TX queues that are used to xmit these frames are the XDP
> queues used by the XDP_TX flow. Therefore a lock is added to synchronize
> both flows (XDP_TX and XDP_REDIRECT).
>
> Signed-off-by: Shay Agroskin <shayagr@...zon.com>
> Signed-off-by: Arthur Kiyanovski <akiyano@...zon.com>
> ---
> drivers/net/ethernet/amazon/ena/ena_netdev.c | 83 +++++++++++++++++---
> drivers/net/ethernet/amazon/ena/ena_netdev.h | 1 +
> 2 files changed, 72 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c
> index 0d077a626604..6c5d8b8c4d13 100644
> --- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
> +++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c
> @@ -281,20 +281,18 @@ static int ena_xdp_tx_map_frame(struct ena_ring *xdp_ring,
> return -EINVAL;
> }
>
> -static int ena_xdp_xmit_frame(struct net_device *dev,
> +static int ena_xdp_xmit_frame(struct ena_ring *xdp_ring,
> + struct net_device *dev,
> struct xdp_frame *xdpf,
> - int qid)
> + int flags)
> {
> - struct ena_adapter *adapter = netdev_priv(dev);
> struct ena_com_tx_ctx ena_tx_ctx = {};
> struct ena_tx_buffer *tx_info;
> - struct ena_ring *xdp_ring;
> u16 next_to_use, req_id;
> - int rc;
> void *push_hdr;
> u32 push_len;
> + int rc;
>
> - xdp_ring = &adapter->tx_ring[qid];
> next_to_use = xdp_ring->next_to_use;
> req_id = xdp_ring->free_ids[next_to_use];
> tx_info = &xdp_ring->tx_buffer_info[req_id];
> @@ -321,25 +319,76 @@ static int ena_xdp_xmit_frame(struct net_device *dev,
> /* trigger the dma engine. ena_com_write_sq_doorbell()
> * has a mb
> */
> - ena_com_write_sq_doorbell(xdp_ring->ena_com_io_sq);
> - ena_increase_stat(&xdp_ring->tx_stats.doorbells, 1, &xdp_ring->syncp);
> + if (flags & XDP_XMIT_FLUSH) {
> + ena_com_write_sq_doorbell(xdp_ring->ena_com_io_sq);
> + ena_increase_stat(&xdp_ring->tx_stats.doorbells, 1,
> + &xdp_ring->syncp);
> + }
>
> - return NETDEV_TX_OK;
> + return rc;
>
> error_unmap_dma:
> ena_unmap_tx_buff(xdp_ring, tx_info);
> tx_info->xdpf = NULL;
> error_drop_packet:
> xdp_return_frame(xdpf);
> - return NETDEV_TX_OK;
> + return rc;
> +}
> +
> +static int ena_xdp_xmit(struct net_device *dev, int n,
> + struct xdp_frame **frames, u32 flags)
> +{
> + struct ena_adapter *adapter = netdev_priv(dev);
> + int qid, i, err, drops = 0;
> + struct ena_ring *xdp_ring;
> +
> + if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
> + return -EINVAL;
> +
> + if (!test_bit(ENA_FLAG_DEV_UP, &adapter->flags))
> + return -ENETDOWN;
> +
> + /* We assume that all rings have the same XDP program */
> + if (!READ_ONCE(adapter->rx_ring->xdp_bpf_prog))
> + return -ENXIO;
> +
> + qid = smp_processor_id() % adapter->xdp_num_queues;
> + qid += adapter->xdp_first_ring;
> + xdp_ring = &adapter->tx_ring[qid];
> +
> + /* Other CPU ids might try to send thorugh this queue */
> + spin_lock(&xdp_ring->xdp_tx_lock);
I have a feeling that we are not consistent with this locking approach as
some drivers do that and some don't.
> +
> + for (i = 0; i < n; i++) {
> + err = ena_xdp_xmit_frame(xdp_ring, dev, frames[i], 0);
> + /* The descriptor is freed by ena_xdp_xmit_frame in case
> + * of an error.
> + */
> + if (err)
> + drops++;
> + }
> +
> + /* Ring doorbell to make device aware of the packets */
> + if (flags & XDP_XMIT_FLUSH) {
> + ena_com_write_sq_doorbell(xdp_ring->ena_com_io_sq);
> + ena_increase_stat(&xdp_ring->tx_stats.doorbells, 1,
> + &xdp_ring->syncp);
Have you thought of ringing the doorbell once per a batch of xmitted
frames?
> + }
> +
> + spin_unlock(&xdp_ring->xdp_tx_lock);
> +
> + /* Return number of packets sent */
> + return n - drops;
> }
>
> static int ena_xdp_execute(struct ena_ring *rx_ring, struct xdp_buff *xdp)
> {
> struct bpf_prog *xdp_prog;
> + struct ena_ring *xdp_ring;
> u32 verdict = XDP_PASS;
> struct xdp_frame *xdpf;
> u64 *xdp_stat;
> + int qid;
>
> rcu_read_lock();
> xdp_prog = READ_ONCE(rx_ring->xdp_bpf_prog);
> @@ -352,8 +401,16 @@ static int ena_xdp_execute(struct ena_ring *rx_ring, struct xdp_buff *xdp)
> switch (verdict) {
> case XDP_TX:
> xdpf = xdp_convert_buff_to_frame(xdp);
> - ena_xdp_xmit_frame(rx_ring->netdev, xdpf,
> - rx_ring->qid + rx_ring->adapter->num_io_queues);
> + /* Find xmit queue */
> + qid = rx_ring->qid + rx_ring->adapter->num_io_queues;
> + xdp_ring = &rx_ring->adapter->tx_ring[qid];
> +
> + /* The XDP queues are shared between XDP_TX and XDP_REDIRECT */
> + spin_lock(&xdp_ring->xdp_tx_lock);
> +
> + ena_xdp_xmit_frame(xdp_ring, rx_ring->netdev, xdpf, XDP_XMIT_FLUSH);
Once again you don't check retval over here.
> +
> + spin_unlock(&xdp_ring->xdp_tx_lock);
> xdp_stat = &rx_ring->rx_stats.xdp_tx;
> break;
> case XDP_REDIRECT:
> @@ -644,6 +701,7 @@ static void ena_init_io_rings(struct ena_adapter *adapter,
> txr->smoothed_interval =
> ena_com_get_nonadaptive_moderation_interval_tx(ena_dev);
> txr->disable_meta_caching = adapter->disable_meta_caching;
> + spin_lock_init(&txr->xdp_tx_lock);
>
> /* Don't init RX queues for xdp queues */
> if (!ENA_IS_XDP_INDEX(adapter, i)) {
> @@ -3236,6 +3294,7 @@ static const struct net_device_ops ena_netdev_ops = {
> .ndo_set_mac_address = NULL,
> .ndo_validate_addr = eth_validate_addr,
> .ndo_bpf = ena_xdp,
> + .ndo_xdp_xmit = ena_xdp_xmit,
> };
>
> static int ena_device_validate_params(struct ena_adapter *adapter,
> diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.h b/drivers/net/ethernet/amazon/ena/ena_netdev.h
> index fed79c50a870..74af15d62ee1 100644
> --- a/drivers/net/ethernet/amazon/ena/ena_netdev.h
> +++ b/drivers/net/ethernet/amazon/ena/ena_netdev.h
> @@ -258,6 +258,7 @@ struct ena_ring {
> struct ena_com_io_sq *ena_com_io_sq;
> struct bpf_prog *xdp_bpf_prog;
> struct xdp_rxq_info xdp_rxq;
> + spinlock_t xdp_tx_lock; /* synchronize XDP TX/Redirect traffic */
>
> u16 next_to_use;
> u16 next_to_clean;
> --
> 2.23.3
>
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