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Message-ID: <c5e39384f185fcb8788e7723498702b0235e367e.camel@gmail.com>
Date: Tue, 10 Jan 2023 09:40:44 -0800
From: Alexander H Duyck <alexander.duyck@...il.com>
To: Gerhard Engleder <gerhard@...leder-embedded.com>,
netdev@...r.kernel.org
Cc: davem@...emloft.net, kuba@...nel.org, edumazet@...gle.com,
pabeni@...hat.com
Subject: Re: [PATCH net-next v4 09/10] tsnep: Add XDP RX support
On Mon, 2023-01-09 at 20:15 +0100, Gerhard Engleder wrote:
> If BPF program is set up, then run BPF program for every received frame
> and execute the selected action.
>
> Signed-off-by: Gerhard Engleder <gerhard@...leder-embedded.com>
> ---
> drivers/net/ethernet/engleder/tsnep_main.c | 122 ++++++++++++++++++++-
> 1 file changed, 120 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/engleder/tsnep_main.c b/drivers/net/ethernet/engleder/tsnep_main.c
> index 451ad1849b9d..002c879639db 100644
> --- a/drivers/net/ethernet/engleder/tsnep_main.c
> +++ b/drivers/net/ethernet/engleder/tsnep_main.c
> @@ -27,6 +27,7 @@
> #include <linux/phy.h>
> #include <linux/iopoll.h>
> #include <linux/bpf.h>
> +#include <linux/bpf_trace.h>
>
> #define TSNEP_SKB_PAD (NET_SKB_PAD + NET_IP_ALIGN)
> #define TSNEP_HEADROOM ALIGN(max(TSNEP_SKB_PAD, XDP_PACKET_HEADROOM), 4)
> @@ -44,6 +45,9 @@
> #define TSNEP_COALESCE_USECS_MAX ((ECM_INT_DELAY_MASK >> ECM_INT_DELAY_SHIFT) * \
> ECM_INT_DELAY_BASE_US + ECM_INT_DELAY_BASE_US - 1)
>
> +#define TSNEP_XDP_TX BIT(0)
> +#define TSNEP_XDP_REDIRECT BIT(1)
> +
> enum {
> __TSNEP_DOWN,
> };
> @@ -625,6 +629,28 @@ static void tsnep_xdp_xmit_flush(struct tsnep_tx *tx)
> iowrite32(TSNEP_CONTROL_TX_ENABLE, tx->addr + TSNEP_CONTROL);
> }
>
> +static bool tsnep_xdp_xmit_back(struct tsnep_adapter *adapter,
> + struct xdp_buff *xdp,
> + struct netdev_queue *tx_nq, struct tsnep_tx *tx)
> +{
> + struct xdp_frame *xdpf = xdp_convert_buff_to_frame(xdp);
> + bool xmit;
> +
> + if (unlikely(!xdpf))
> + return false;
> +
> + __netif_tx_lock(tx_nq, smp_processor_id());
> +
> + /* Avoid transmit queue timeout since we share it with the slow path */
> + txq_trans_cond_update(tx_nq);
> +
> + xmit = tsnep_xdp_xmit_frame_ring(xdpf, tx, TSNEP_TX_TYPE_XDP_TX);
> +
Again the trans_cond_update should be after the xmit and only if it is
not indicating it completed the transmit.
> + __netif_tx_unlock(tx_nq);
> +
> + return xmit;
> +}
> +
> static bool tsnep_tx_poll(struct tsnep_tx *tx, int napi_budget)
> {
> struct tsnep_tx_entry *entry;
> @@ -983,6 +1009,62 @@ static int tsnep_rx_refill(struct tsnep_rx *rx, int count, bool reuse)
> return i;
> }
>
> +static bool tsnep_xdp_run_prog(struct tsnep_rx *rx, struct bpf_prog *prog,
> + struct xdp_buff *xdp, int *status,
> + struct netdev_queue *tx_nq, struct tsnep_tx *tx)
> +{
> + unsigned int length;
> + unsigned int sync;
> + u32 act;
> +
> + length = xdp->data_end - xdp->data_hard_start - XDP_PACKET_HEADROOM;
> +
> + act = bpf_prog_run_xdp(prog, xdp);
> +
> + /* Due xdp_adjust_tail: DMA sync for_device cover max len CPU touch */
> + sync = xdp->data_end - xdp->data_hard_start - XDP_PACKET_HEADROOM;
> + sync = max(sync, length);
> +
> + switch (act) {
> + case XDP_PASS:
> + return false;
> + case XDP_TX:
> + if (!tsnep_xdp_xmit_back(rx->adapter, xdp, tx_nq, tx))
> + goto out_failure;
> + *status |= TSNEP_XDP_TX;
> + return true;
> + case XDP_REDIRECT:
> + if (xdp_do_redirect(rx->adapter->netdev, xdp, prog) < 0)
> + goto out_failure;
> + *status |= TSNEP_XDP_REDIRECT;
> + return true;
> + default:
> + bpf_warn_invalid_xdp_action(rx->adapter->netdev, prog, act);
> + fallthrough;
> + case XDP_ABORTED:
> +out_failure:
> + trace_xdp_exception(rx->adapter->netdev, prog, act);
> + fallthrough;
> + case XDP_DROP:
> + page_pool_put_page(rx->page_pool, virt_to_head_page(xdp->data),
> + sync, true);
> + return true;
> + }
> +}
> +
> +static void tsnep_finalize_xdp(struct tsnep_adapter *adapter, int status,
> + struct netdev_queue *tx_nq, struct tsnep_tx *tx)
> +{
> + if (status & TSNEP_XDP_TX) {
> + __netif_tx_lock(tx_nq, smp_processor_id());
> + tsnep_xdp_xmit_flush(tx);
> + __netif_tx_unlock(tx_nq);
> + }
> +
> + if (status & TSNEP_XDP_REDIRECT)
> + xdp_do_flush();
> +}
> +
> static struct sk_buff *tsnep_build_skb(struct tsnep_rx *rx, struct page *page,
> int length)
> {
> @@ -1018,15 +1100,29 @@ static int tsnep_rx_poll(struct tsnep_rx *rx, struct napi_struct *napi,
> int budget)
> {
> struct device *dmadev = rx->adapter->dmadev;
> - int desc_available;
> - int done = 0;
> enum dma_data_direction dma_dir;
> struct tsnep_rx_entry *entry;
> + struct netdev_queue *tx_nq;
> + struct bpf_prog *prog;
> + struct xdp_buff xdp;
> struct sk_buff *skb;
> + struct tsnep_tx *tx;
> + int desc_available;
> + int xdp_status = 0;
> + int done = 0;
> int length;
>
> desc_available = tsnep_rx_desc_available(rx);
> dma_dir = page_pool_get_dma_dir(rx->page_pool);
> + prog = READ_ONCE(rx->adapter->xdp_prog);
> + if (prog) {
> + int queue = smp_processor_id() % rx->adapter->num_tx_queues;
> +
As I mentioned before. Take a look at how this was addressed in
skb_tx_hash. The modulus division is really expensive.
Also does this make sense. I am assuming you have a 1:1 Tx to Rx
mapping for your queues don't you? If so it might make more sense to
use the Tx queue that you clean in this queue pair.
> + tx_nq = netdev_get_tx_queue(rx->adapter->netdev, queue);
> + tx = &rx->adapter->tx[queue];
> +
> + xdp_init_buff(&xdp, PAGE_SIZE, &rx->xdp_rxq);
> + }
>
> while (likely(done < budget) && (rx->read != rx->write)) {
> entry = &rx->entry[rx->read];
> @@ -1076,6 +1172,25 @@ static int tsnep_rx_poll(struct tsnep_rx *rx, struct napi_struct *napi,
> rx->read = (rx->read + 1) % TSNEP_RING_SIZE;
> desc_available++;
>
> + if (prog) {
> + bool consume;
> +
> + xdp_prepare_buff(&xdp, page_address(entry->page),
> + XDP_PACKET_HEADROOM + TSNEP_RX_INLINE_METADATA_SIZE,
> + length, false);
> +
> + consume = tsnep_xdp_run_prog(rx, prog, &xdp,
> + &xdp_status, tx_nq, tx);
> + if (consume) {
> + rx->packets++;
> + rx->bytes += length;
> +
> + entry->page = NULL;
> +
> + continue;
> + }
> + }
> +
> skb = tsnep_build_skb(rx, entry->page, length);
> if (skb) {
> page_pool_release_page(rx->page_pool, entry->page);
> @@ -1094,6 +1209,9 @@ static int tsnep_rx_poll(struct tsnep_rx *rx, struct napi_struct *napi,
> entry->page = NULL;
> }
>
> + if (xdp_status)
> + tsnep_finalize_xdp(rx->adapter, xdp_status, tx_nq, tx);
> +
> if (desc_available)
> tsnep_rx_refill(rx, desc_available, false);
>
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