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Date: Tue, 22 Nov 2022 23:27:07 +0100
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: Horatiu Vultur <horatiu.vultur@...rochip.com>
CC: <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<bpf@...r.kernel.org>, <davem@...emloft.net>,
<edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
<ast@...nel.org>, <daniel@...earbox.net>, <hawk@...nel.org>,
<john.fastabend@...il.com>, <alexandr.lobakin@...el.com>,
<UNGLinuxDriver@...rochip.com>
Subject: Re: [PATCH net-next v4 6/7] net: lan966x: Add support for XDP_TX
On Tue, Nov 22, 2022 at 10:44:12PM +0100, Horatiu Vultur wrote:
> Extend lan966x XDP support with the action XDP_TX. In this case when the
> received buffer needs to execute XDP_TX, the buffer will be moved to the
> TX buffers. So a new RX buffer will be allocated.
> When the TX finish with the frame, it would give back the buffer to the
> page pool.
>
> Signed-off-by: Horatiu Vultur <horatiu.vultur@...rochip.com>
> ---
> .../ethernet/microchip/lan966x/lan966x_fdma.c | 78 +++++++++++++++++--
> .../ethernet/microchip/lan966x/lan966x_main.c | 4 +-
> .../ethernet/microchip/lan966x/lan966x_main.h | 8 ++
> .../ethernet/microchip/lan966x/lan966x_xdp.c | 8 ++
> 4 files changed, 90 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
> index f8287a6a86ed5..23e1cad0f5d37 100644
> --- a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
> +++ b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
> @@ -411,12 +411,18 @@ static void lan966x_fdma_tx_clear_buf(struct lan966x *lan966x, int weight)
> dcb_buf->dev->stats.tx_bytes += dcb_buf->len;
>
> dcb_buf->used = false;
> - dma_unmap_single(lan966x->dev,
> - dcb_buf->dma_addr,
> - dcb_buf->len,
> - DMA_TO_DEVICE);
> - if (!dcb_buf->ptp)
> - dev_kfree_skb_any(dcb_buf->skb);
> + if (dcb_buf->skb) {
> + dma_unmap_single(lan966x->dev,
> + dcb_buf->dma_addr,
> + dcb_buf->len,
> + DMA_TO_DEVICE);
> +
> + if (!dcb_buf->ptp)
> + napi_consume_skb(dcb_buf->skb, weight);
> + }
> +
> + if (dcb_buf->xdpf)
> + xdp_return_frame_rx_napi(dcb_buf->xdpf);
>
> clear = true;
> }
> @@ -549,6 +555,9 @@ static int lan966x_fdma_napi_poll(struct napi_struct *napi, int weight)
> lan966x_fdma_rx_free_page(rx);
> lan966x_fdma_rx_advance_dcb(rx);
> goto allocate_new;
> + case FDMA_TX:
> + lan966x_fdma_rx_advance_dcb(rx);
> + continue;
> case FDMA_DROP:
> lan966x_fdma_rx_free_page(rx);
> lan966x_fdma_rx_advance_dcb(rx);
> @@ -670,6 +679,62 @@ static void lan966x_fdma_tx_start(struct lan966x_tx *tx, int next_to_use)
> tx->last_in_use = next_to_use;
> }
>
> +int lan966x_fdma_xmit_xdpf(struct lan966x_port *port,
> + struct xdp_frame *xdpf,
> + struct page *page)
> +{
> + struct lan966x *lan966x = port->lan966x;
> + struct lan966x_tx_dcb_buf *next_dcb_buf;
> + struct lan966x_tx *tx = &lan966x->tx;
> + dma_addr_t dma_addr;
> + int next_to_use;
> + __be32 *ifh;
> + int ret = 0;
> +
> + spin_lock(&lan966x->tx_lock);
> +
> + /* Get next index */
> + next_to_use = lan966x_fdma_get_next_dcb(tx);
> + if (next_to_use < 0) {
> + netif_stop_queue(port->dev);
> + ret = NETDEV_TX_BUSY;
> + goto out;
> + }
> +
> + /* Generate new IFH */
> + ifh = page_address(page) + XDP_PACKET_HEADROOM;
> + memset(ifh, 0x0, sizeof(__be32) * IFH_LEN);
> + lan966x_ifh_set_bypass(ifh, 1);
> + lan966x_ifh_set_port(ifh, BIT_ULL(port->chip_port));
> +
> + dma_addr = page_pool_get_dma_addr(page);
> + dma_sync_single_for_device(lan966x->dev, dma_addr + XDP_PACKET_HEADROOM,
> + xdpf->len + IFH_LEN_BYTES,
> + DMA_TO_DEVICE);
> +
> + /* Setup next dcb */
> + lan966x_fdma_tx_setup_dcb(tx, next_to_use, xdpf->len + IFH_LEN_BYTES,
> + dma_addr + XDP_PACKET_HEADROOM);
> +
> + /* Fill up the buffer */
> + next_dcb_buf = &tx->dcbs_buf[next_to_use];
> + next_dcb_buf->skb = NULL;
> + next_dcb_buf->xdpf = xdpf;
> + next_dcb_buf->len = xdpf->len + IFH_LEN_BYTES;
> + next_dcb_buf->dma_addr = dma_addr;
> + next_dcb_buf->used = true;
> + next_dcb_buf->ptp = false;
> + next_dcb_buf->dev = port->dev;
> +
> + /* Start the transmission */
> + lan966x_fdma_tx_start(tx, next_to_use);
> +
> +out:
> + spin_unlock(&lan966x->tx_lock);
> +
> + return ret;
> +}
> +
> int lan966x_fdma_xmit(struct sk_buff *skb, __be32 *ifh, struct net_device *dev)
> {
> struct lan966x_port *port = netdev_priv(dev);
> @@ -726,6 +791,7 @@ int lan966x_fdma_xmit(struct sk_buff *skb, __be32 *ifh, struct net_device *dev)
> /* Fill up the buffer */
> next_dcb_buf = &tx->dcbs_buf[next_to_use];
> next_dcb_buf->skb = skb;
> + next_dcb_buf->xdpf = NULL;
> next_dcb_buf->len = skb->len;
> next_dcb_buf->dma_addr = dma_addr;
> next_dcb_buf->used = true;
> diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_main.c b/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
> index 42be5d0f1f015..0b7707306da26 100644
> --- a/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
> +++ b/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
> @@ -302,13 +302,13 @@ static int lan966x_port_ifh_xmit(struct sk_buff *skb,
> return NETDEV_TX_BUSY;
> }
>
> -static void lan966x_ifh_set_bypass(void *ifh, u64 bypass)
> +void lan966x_ifh_set_bypass(void *ifh, u64 bypass)
> {
> packing(ifh, &bypass, IFH_POS_BYPASS + IFH_WID_BYPASS - 1,
> IFH_POS_BYPASS, IFH_LEN * 4, PACK, 0);
> }
>
> -static void lan966x_ifh_set_port(void *ifh, u64 bypass)
> +void lan966x_ifh_set_port(void *ifh, u64 bypass)
> {
> packing(ifh, &bypass, IFH_POS_DSTS + IFH_WID_DSTS - 1,
> IFH_POS_DSTS, IFH_LEN * 4, PACK, 0);
> diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_main.h b/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
> index 81c0b11097ce2..ce8b2eb13a9aa 100644
> --- a/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
> +++ b/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
> @@ -105,11 +105,13 @@ enum macaccess_entry_type {
> * FDMA_PASS, frame is valid and can be used
> * FDMA_ERROR, something went wrong, stop getting more frames
> * FDMA_DROP, frame is dropped, but continue to get more frames
> + * FDMA_TX, frame is given to TX, but continue to get more frames
> */
> enum lan966x_fdma_action {
> FDMA_PASS = 0,
> FDMA_ERROR,
> FDMA_DROP,
> + FDMA_TX,
> };
>
> struct lan966x_port;
> @@ -176,6 +178,7 @@ struct lan966x_tx_dcb_buf {
> dma_addr_t dma_addr;
> struct net_device *dev;
> struct sk_buff *skb;
> + struct xdp_frame *xdpf;
Couldn't you make an union out of skb and xdpf? I'd say these two are
mutually exclusive, no? I believe this would simplify some things.
> u32 len;
> u32 used : 1;
> u32 ptp : 1;
> @@ -360,6 +363,8 @@ bool lan966x_hw_offload(struct lan966x *lan966x, u32 port, struct sk_buff *skb);
>
> void lan966x_ifh_get_src_port(void *ifh, u64 *src_port);
> void lan966x_ifh_get_timestamp(void *ifh, u64 *timestamp);
> +void lan966x_ifh_set_bypass(void *ifh, u64 bypass);
> +void lan966x_ifh_set_port(void *ifh, u64 bypass);
>
> void lan966x_stats_get(struct net_device *dev,
> struct rtnl_link_stats64 *stats);
> @@ -460,6 +465,9 @@ u32 lan966x_ptp_get_period_ps(void);
> int lan966x_ptp_gettime64(struct ptp_clock_info *ptp, struct timespec64 *ts);
>
> int lan966x_fdma_xmit(struct sk_buff *skb, __be32 *ifh, struct net_device *dev);
> +int lan966x_fdma_xmit_xdpf(struct lan966x_port *port,
> + struct xdp_frame *frame,
> + struct page *page);
> int lan966x_fdma_change_mtu(struct lan966x *lan966x);
> void lan966x_fdma_netdev_init(struct lan966x *lan966x, struct net_device *dev);
> void lan966x_fdma_netdev_deinit(struct lan966x *lan966x, struct net_device *dev);
> diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_xdp.c b/drivers/net/ethernet/microchip/lan966x/lan966x_xdp.c
> index a99657154cca4..e7998fef7048c 100644
> --- a/drivers/net/ethernet/microchip/lan966x/lan966x_xdp.c
> +++ b/drivers/net/ethernet/microchip/lan966x/lan966x_xdp.c
> @@ -54,6 +54,7 @@ int lan966x_xdp_run(struct lan966x_port *port, struct page *page, u32 data_len)
> {
> struct bpf_prog *xdp_prog = port->xdp_prog;
> struct lan966x *lan966x = port->lan966x;
> + struct xdp_frame *xdpf;
> struct xdp_buff xdp;
> u32 act;
>
> @@ -66,6 +67,13 @@ int lan966x_xdp_run(struct lan966x_port *port, struct page *page, u32 data_len)
> switch (act) {
> case XDP_PASS:
> return FDMA_PASS;
> + case XDP_TX:
> + xdpf = xdp_convert_buff_to_frame(&xdp);
> + if (!xdpf)
> + return FDMA_DROP;
I would generally challenge the need for xdp_frame in XDP_TX path. You
probably would be good to go with calling directly
page_pool_put_full_page() on cleaning side. This frame is not going to be
redirected so I don't see the need for carrying additional info. I'm
bringing this up as I was observing performance improvement on ice driver
when I decided to operate directly on xdp_buff for XDP_TX.
But it's of course up to you.
> +
> + return lan966x_fdma_xmit_xdpf(port, xdpf, page) ?
> + FDMA_DROP : FDMA_TX;
> default:
> bpf_warn_invalid_xdp_action(port->dev, xdp_prog, act);
> fallthrough;
> --
> 2.38.0
>
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