Subject: Re: [PATCH v3 bpf-next 2/2] net: xdp: introduce xdp_prepare_buff utility routine

From: Maciej Fijalkowski <[email-masked]>
Date: Tue, 15 Dec 2020 13:36:43 +0100

On Sat, Dec 12, 2020 at 06:41:49PM +0100, Lorenzo Bianconi wrote:
> Introduce xdp_prepare_buff utility routine to initialize per-descriptor
> xdp_buff fields (e.g. xdp_buff pointers). Rely on xdp_prepare_buff() in
> all XDP capable drivers.
> 
> Signed-off-by: Lorenzo Bianconi <[email-masked]>
> ---
>  drivers/net/ethernet/amazon/ena/ena_netdev.c      |  5 ++---
>  drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c     |  4 +---
>  drivers/net/ethernet/cavium/thunder/nicvf_main.c  |  7 ++++---
>  drivers/net/ethernet/freescale/dpaa/dpaa_eth.c    |  6 ++----
>  drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c  | 13 +++++--------
>  drivers/net/ethernet/intel/i40e/i40e_txrx.c       | 12 ++++++------
>  drivers/net/ethernet/intel/ice/ice_txrx.c         | 11 ++++++-----
>  drivers/net/ethernet/intel/igb/igb_main.c         | 12 ++++++------
>  drivers/net/ethernet/intel/ixgbe/ixgbe_main.c     | 12 ++++++------
>  drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c | 12 ++++++------
>  drivers/net/ethernet/marvell/mvneta.c             |  6 ++----
>  drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c   |  7 +++----
>  drivers/net/ethernet/mellanox/mlx4/en_rx.c        |  5 ++---
>  drivers/net/ethernet/mellanox/mlx5/core/en_rx.c   |  4 +---
>  .../net/ethernet/netronome/nfp/nfp_net_common.c   |  8 ++++----
>  drivers/net/ethernet/qlogic/qede/qede_fp.c        |  4 +---
>  drivers/net/ethernet/sfc/rx.c                     |  6 ++----
>  drivers/net/ethernet/socionext/netsec.c           |  5 ++---
>  drivers/net/ethernet/ti/cpsw.c                    | 15 +++++----------
>  drivers/net/ethernet/ti/cpsw_new.c                | 15 +++++----------
>  drivers/net/hyperv/netvsc_bpf.c                   |  4 +---
>  drivers/net/tun.c                                 |  4 +---
>  drivers/net/veth.c                                |  6 +-----
>  drivers/net/virtio_net.c                          | 12 ++++--------
>  drivers/net/xen-netfront.c                        |  4 +---
>  include/net/xdp.h                                 | 12 ++++++++++++
>  net/bpf/test_run.c                                |  5 +----
>  net/core/dev.c                                    | 10 ++++------
>  28 files changed, 96 insertions(+), 130 deletions(-)
> 
> diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c
> index 338dce73927e..1cfd0c98677e 100644
> --- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
> +++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c
> @@ -1519,10 +1519,9 @@ static int ena_xdp_handle_buff(struct ena_ring *rx_ring, struct xdp_buff *xdp)
>  	int ret;
>  
>  	rx_info = &rx_ring->rx_buffer_info[rx_ring->ena_bufs[0].req_id];
> -	xdp->data = page_address(rx_info->page) + rx_info->page_offset;
> +	xdp_prepare_buff(xdp, page_address(rx_info->page),
> +			 rx_info->page_offset, rx_ring->ena_bufs[0].len);
>  	xdp_set_data_meta_invalid(xdp);
> -	xdp->data_hard_start = page_address(rx_info->page);
> -	xdp->data_end = xdp->data + rx_ring->ena_bufs[0].len;
>  	/* If for some reason we received a bigger packet than
>  	 * we expect, then we simply drop it
>  	 */
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
> index b7942c3440c0..e1664b86a7b8 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
> @@ -134,10 +134,8 @@ bool bnxt_rx_xdp(struct bnxt *bp, struct bnxt_rx_ring_info *rxr, u16 cons,
>  
>  	txr = rxr->bnapi->tx_ring;
>  	xdp_init_buff(&xdp, PAGE_SIZE, &rxr->xdp_rxq);
> -	xdp.data_hard_start = *data_ptr - offset;
> -	xdp.data = *data_ptr;
> +	xdp_prepare_buff(&xdp, *data_ptr - offset, offset, *len);
>  	xdp_set_data_meta_invalid(&xdp);
> -	xdp.data_end = *data_ptr + *len;
>  	orig_data = xdp.data;
>  
>  	rcu_read_lock();
> diff --git a/drivers/net/ethernet/cavium/thunder/nicvf_main.c b/drivers/net/ethernet/cavium/thunder/nicvf_main.c
> index 9fc672f075f2..9bdac04359c6 100644
> --- a/drivers/net/ethernet/cavium/thunder/nicvf_main.c
> +++ b/drivers/net/ethernet/cavium/thunder/nicvf_main.c
> @@ -530,6 +530,7 @@ static inline bool nicvf_xdp_rx(struct nicvf *nic, struct bpf_prog *prog,
>  				struct cqe_rx_t *cqe_rx, struct snd_queue *sq,
>  				struct rcv_queue *rq, struct sk_buff **skb)
>  {
> +	unsigned char *hard_start, *data;
>  	struct xdp_buff xdp;
>  	struct page *page;
>  	u32 action;
> @@ -549,10 +550,10 @@ static inline bool nicvf_xdp_rx(struct nicvf *nic, struct bpf_prog *prog,
>  
>  	xdp_init_buff(&xdp, RCV_FRAG_LEN + XDP_PACKET_HEADROOM,
>  		      &rq->xdp_rxq);
> -	xdp.data_hard_start = page_address(page);
> -	xdp.data = (void *)cpu_addr;
> +	hard_start = page_address(page);
> +	data = (unsigned char *)cpu_addr;
> +	xdp_prepare_buff(&xdp, hard_start, data - hard_start, len);
>  	xdp_set_data_meta_invalid(&xdp);
> -	xdp.data_end = xdp.data + len;
>  	orig_data = xdp.data;
>  
>  	rcu_read_lock();
> diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> index 93030000e0aa..86ee07c90154 100644
> --- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> +++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> @@ -2538,10 +2538,8 @@ static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd, void *vaddr,
>  
>  	xdp_init_buff(&xdp, DPAA_BP_RAW_SIZE - DPAA_TX_PRIV_DATA_SIZE,
>  		      &dpaa_fq->xdp_rxq);
> -	xdp.data = vaddr + fd_off;
> -	xdp.data_meta = xdp.data;
> -	xdp.data_hard_start = xdp.data - XDP_PACKET_HEADROOM;
> -	xdp.data_end = xdp.data + qm_fd_get_length(fd);
> +	xdp_prepare_buff(&xdp, vaddr + fd_off - XDP_PACKET_HEADROOM,
> +			 XDP_PACKET_HEADROOM, qm_fd_get_length(fd));
>  
>  	/* We reserve a fixed headroom of 256 bytes under the erratum and we
>  	 * offer it all to XDP programs to use. If no room is left for the
> diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
> index a4ade0b5adb0..12358f5d59d6 100644
> --- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
> +++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
> @@ -350,7 +350,7 @@ static u32 dpaa2_eth_run_xdp(struct dpaa2_eth_priv *priv,
>  	struct bpf_prog *xdp_prog;
>  	struct xdp_buff xdp;
>  	u32 xdp_act = XDP_PASS;
> -	int err;
> +	int err, offset;
>  
>  	rcu_read_lock();
>  
> @@ -358,13 +358,10 @@ static u32 dpaa2_eth_run_xdp(struct dpaa2_eth_priv *priv,
>  	if (!xdp_prog)
>  		goto out;
>  
> -	xdp_init_buff(&xdp,
> -		      DPAA2_ETH_RX_BUF_RAW_SIZE -
> -		      (dpaa2_fd_get_offset(fd) - XDP_PACKET_HEADROOM),
> -		      &ch->xdp_rxq);
> -	xdp.data = vaddr + dpaa2_fd_get_offset(fd);
> -	xdp.data_end = xdp.data + dpaa2_fd_get_len(fd);
> -	xdp.data_hard_start = xdp.data - XDP_PACKET_HEADROOM;
> +	offset = dpaa2_fd_get_offset(fd) - XDP_PACKET_HEADROOM;
> +	xdp_init_buff(&xdp, DPAA2_ETH_RX_BUF_RAW_SIZE - offset, &ch->xdp_rxq);
> +	xdp_prepare_buff(&xdp, vaddr + offset, XDP_PACKET_HEADROOM,
> +			 dpaa2_fd_get_len(fd));
>  	xdp_set_data_meta_invalid(&xdp);
>  
>  	xdp_act = bpf_prog_run_xdp(xdp_prog, &xdp);
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> index 4dbbbd49c389..fcd1ca3343fb 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> @@ -2393,12 +2393,12 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget)
>  
>  		/* retrieve a buffer from the ring */
>  		if (!skb) {
> -			xdp.data = page_address(rx_buffer->page) +
> -				   rx_buffer->page_offset;
> -			xdp.data_meta = xdp.data;
> -			xdp.data_hard_start = xdp.data -
> -					      i40e_rx_offset(rx_ring);
> -			xdp.data_end = xdp.data + size;
> +			unsigned int offset = i40e_rx_offset(rx_ring);

I now see that we could call the i40e_rx_offset() once per napi, so can
you pull this variable out and have it initialized a single time? Applies
to other intel drivers as well.

I also feel like it's sub-optimal for drivers that are calculating the
data_hard_start out of data (intel, bnxt, sfc and mlx4 have this approach)
due to additional add, but I don't have a solution for that. Would be
weird to have another helper. Not sure what other people think, but I have
in mind a "death by 1000 cuts" phrase :)

> +			unsigned char *hard_start;
> +
> +			hard_start = page_address(rx_buffer->page) +
> +				     rx_buffer->page_offset - offset;
> +			xdp_prepare_buff(&xdp, hard_start, offset, size);
>  #if (PAGE_SIZE > 4096)
>  			/* At larger PAGE_SIZE, frame_sz depend on len size */
>  			xdp.frame_sz = i40e_rx_frame_truesize(rx_ring, size);
> diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.c b/drivers/net/ethernet/intel/ice/ice_txrx.c
> index d52d98d56367..a7a00060f520 100644
> --- a/drivers/net/ethernet/intel/ice/ice_txrx.c
> +++ b/drivers/net/ethernet/intel/ice/ice_txrx.c
> @@ -1094,8 +1094,9 @@ int ice_clean_rx_irq(struct ice_ring *rx_ring, int budget)
>  	while (likely(total_rx_pkts < (unsigned int)budget)) {
>  		union ice_32b_rx_flex_desc *rx_desc;
>  		struct ice_rx_buf *rx_buf;
> +		unsigned int size, offset;
> +		unsigned char *hard_start;
>  		struct sk_buff *skb;
> -		unsigned int size;
>  		u16 stat_err_bits;
>  		u16 vlan_tag = 0;
>  		u8 rx_ptype;
> @@ -1138,10 +1139,10 @@ int ice_clean_rx_irq(struct ice_ring *rx_ring, int budget)
>  			goto construct_skb;
>  		}
>  
> -		xdp.data = page_address(rx_buf->page) + rx_buf->page_offset;
> -		xdp.data_hard_start = xdp.data - ice_rx_offset(rx_ring);
> -		xdp.data_meta = xdp.data;
> -		xdp.data_end = xdp.data + size;
> +		offset = ice_rx_offset(rx_ring);
> +		hard_start = page_address(rx_buf->page) + rx_buf->page_offset -
> +			     offset;
> +		xdp_prepare_buff(&xdp, hard_start, offset, size);
>  #if (PAGE_SIZE > 4096)
>  		/* At larger PAGE_SIZE, frame_sz depend on len size */
>  		xdp.frame_sz = ice_rx_frame_truesize(rx_ring, size);
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
> index 365dfc0e3b65..070b2bb4e9ca 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -8700,12 +8700,12 @@ static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
>  
>  		/* retrieve a buffer from the ring */
>  		if (!skb) {
> -			xdp.data = page_address(rx_buffer->page) +
> -				   rx_buffer->page_offset;
> -			xdp.data_meta = xdp.data;
> -			xdp.data_hard_start = xdp.data -
> -					      igb_rx_offset(rx_ring);
> -			xdp.data_end = xdp.data + size;
> +			unsigned int offset = igb_rx_offset(rx_ring);
> +			unsigned char *hard_start;
> +
> +			hard_start = page_address(rx_buffer->page) +
> +				     rx_buffer->page_offset - offset;
> +			xdp_prepare_buff(&xdp, hard_start, offset, size);
>  #if (PAGE_SIZE > 4096)
>  			/* At larger PAGE_SIZE, frame_sz depend on len size */
>  			xdp.frame_sz = igb_rx_frame_truesize(rx_ring, size);
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> index dcd49cfa36f7..e34054433c7a 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> @@ -2325,12 +2325,12 @@ static int ixgbe_clean_rx_irq(struct ixgbe_q_vector *q_vector,
>  
>  		/* retrieve a buffer from the ring */
>  		if (!skb) {
> -			xdp.data = page_address(rx_buffer->page) +
> -				   rx_buffer->page_offset;
> -			xdp.data_meta = xdp.data;
> -			xdp.data_hard_start = xdp.data -
> -					      ixgbe_rx_offset(rx_ring);
> -			xdp.data_end = xdp.data + size;
> +			unsigned int offset = ixgbe_rx_offset(rx_ring);
> +			unsigned char *hard_start;
> +
> +			hard_start = page_address(rx_buffer->page) +
> +				     rx_buffer->page_offset - offset;
> +			xdp_prepare_buff(&xdp, hard_start, offset, size);
>  #if (PAGE_SIZE > 4096)
>  			/* At larger PAGE_SIZE, frame_sz depend on len size */
>  			xdp.frame_sz = ixgbe_rx_frame_truesize(rx_ring, size);
> diff --git a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
> index 624efcd71569..51df79005ccb 100644
> --- a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
> +++ b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
> @@ -1160,12 +1160,12 @@ static int ixgbevf_clean_rx_irq(struct ixgbevf_q_vector *q_vector,
>  
>  		/* retrieve a buffer from the ring */
>  		if (!skb) {
> -			xdp.data = page_address(rx_buffer->page) +
> -				   rx_buffer->page_offset;
> -			xdp.data_meta = xdp.data;
> -			xdp.data_hard_start = xdp.data -
> -					      ixgbevf_rx_offset(rx_ring);
> -			xdp.data_end = xdp.data + size;
> +			unsigned int offset = ixgbevf_rx_offset(rx_ring);
> +			unsigned char *hard_start;
> +
> +			hard_start = page_address(rx_buffer->page) +
> +				     rx_buffer->page_offset - offset;
> +			xdp_prepare_buff(&xdp, hard_start, offset, size);
>  #if (PAGE_SIZE > 4096)
>  			/* At larger PAGE_SIZE, frame_sz depend on len size */
>  			xdp.frame_sz = ixgbevf_rx_frame_truesize(rx_ring, size);
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index acbb9cb85ada..af6c9cf59809 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -2263,10 +2263,8 @@ mvneta_swbm_rx_frame(struct mvneta_port *pp,
>  
>  	/* Prefetch header */
>  	prefetch(data);
> -
> -	xdp->data_hard_start = data;
> -	xdp->data = data + pp->rx_offset_correction + MVNETA_MH_SIZE;
> -	xdp->data_end = xdp->data + data_len;
> +	xdp_prepare_buff(xdp, data, pp->rx_offset_correction + MVNETA_MH_SIZE,
> +			 data_len);
>  	xdp_set_data_meta_invalid(xdp);
>  
>  	sinfo = xdp_get_shared_info_from_buff(xdp);
> diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> index ca05dfc05058..8c2197b96515 100644
> --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> @@ -3564,16 +3564,15 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi,
>  		if (xdp_prog) {
>  			struct xdp_rxq_info *xdp_rxq;
>  
> -			xdp.data_hard_start = data;
> -			xdp.data = data + MVPP2_MH_SIZE + MVPP2_SKB_HEADROOM;
> -			xdp.data_end = xdp.data + rx_bytes;
> -
>  			if (bm_pool->pkt_size == MVPP2_BM_SHORT_PKT_SIZE)
>  				xdp_rxq = &rxq->xdp_rxq_short;
>  			else
>  				xdp_rxq = &rxq->xdp_rxq_long;
>  
>  			xdp_init_buff(&xdp, PAGE_SIZE, xdp_rxq);
> +			xdp_prepare_buff(&xdp, data,
> +					 MVPP2_MH_SIZE + MVPP2_SKB_HEADROOM,
> +					 rx_bytes);
>  			xdp_set_data_meta_invalid(&xdp);
>  
>  			ret = mvpp2_run_xdp(port, rxq, xdp_prog, &xdp, pp, &ps);
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_rx.c b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> index 815381b484ca..86c63dedc689 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> @@ -776,10 +776,9 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud
>  						priv->frag_info[0].frag_size,
>  						DMA_FROM_DEVICE);
>  
> -			xdp.data_hard_start = va - frags[0].page_offset;
> -			xdp.data = va;
> +			xdp_prepare_buff(&xdp, va - frags[0].page_offset,
> +					 frags[0].page_offset, length);
>  			xdp_set_data_meta_invalid(&xdp);
> -			xdp.data_end = xdp.data + length;
>  			orig_data = xdp.data;
>  
>  			act = bpf_prog_run_xdp(xdp_prog, &xdp);
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
> index c68628b1f30b..a2f4f0ce427f 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
> @@ -1128,10 +1128,8 @@ static void mlx5e_fill_xdp_buff(struct mlx5e_rq *rq, void *va, u16 headroom,
>  				u32 len, struct xdp_buff *xdp)
>  {
>  	xdp_init_buff(xdp, rq->buff.frame0_sz, &rq->xdp_rxq);
> -	xdp->data_hard_start = va;
> -	xdp->data = va + headroom;
> +	xdp_prepare_buff(xdp, va, headroom, len);
>  	xdp_set_data_meta_invalid(xdp);
> -	xdp->data_end = xdp->data + len;
>  }
>  
>  static struct sk_buff *
> diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
> index 68e03e8257f2..5d0046c24b8c 100644
> --- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
> +++ b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
> @@ -1914,10 +1914,10 @@ static int nfp_net_rx(struct nfp_net_rx_ring *rx_ring, int budget)
>  			unsigned int dma_off;
>  			int act;
>  
> -			xdp.data_hard_start = rxbuf->frag + NFP_NET_RX_BUF_HEADROOM;
> -			xdp.data = orig_data;
> -			xdp.data_meta = orig_data;
> -			xdp.data_end = orig_data + pkt_len;
> +			xdp_prepare_buff(&xdp,
> +					 rxbuf->frag + NFP_NET_RX_BUF_HEADROOM,
> +					 pkt_off - NFP_NET_RX_BUF_HEADROOM,
> +					 pkt_len);
>  
>  			act = bpf_prog_run_xdp(xdp_prog, &xdp);
>  
> diff --git a/drivers/net/ethernet/qlogic/qede/qede_fp.c b/drivers/net/ethernet/qlogic/qede/qede_fp.c
> index d40220043883..9c50df499046 100644
> --- a/drivers/net/ethernet/qlogic/qede/qede_fp.c
> +++ b/drivers/net/ethernet/qlogic/qede/qede_fp.c
> @@ -1091,10 +1091,8 @@ static bool qede_rx_xdp(struct qede_dev *edev,
>  	enum xdp_action act;
>  
>  	xdp_init_buff(&xdp, rxq->rx_buf_seg_size, &rxq->xdp_rxq);
> -	xdp.data_hard_start = page_address(bd->data);
> -	xdp.data = xdp.data_hard_start + *data_offset;
> +	xdp_prepare_buff(&xdp, page_address(bd->data), *data_offset, *len);
>  	xdp_set_data_meta_invalid(&xdp);
> -	xdp.data_end = xdp.data + *len;
>  
>  	/* Queues always have a full reset currently, so for the time
>  	 * being until there's atomic program replace just mark read
> diff --git a/drivers/net/ethernet/sfc/rx.c b/drivers/net/ethernet/sfc/rx.c
> index eaa6650955d1..9015a1639234 100644
> --- a/drivers/net/ethernet/sfc/rx.c
> +++ b/drivers/net/ethernet/sfc/rx.c
> @@ -294,12 +294,10 @@ static bool efx_do_xdp(struct efx_nic *efx, struct efx_channel *channel,
>  	       efx->rx_prefix_size);
>  
>  	xdp_init_buff(&xdp, efx->rx_page_buf_step, &rx_queue->xdp_rxq_info);
> -	xdp.data = *ehp;
> -	xdp.data_hard_start = xdp.data - EFX_XDP_HEADROOM;
> -
> +	xdp_prepare_buff(&xdp, *ehp - EFX_XDP_HEADROOM, EFX_XDP_HEADROOM,
> +			 rx_buf->len);
>  	/* No support yet for XDP metadata */
>  	xdp_set_data_meta_invalid(&xdp);
> -	xdp.data_end = xdp.data + rx_buf->len;
>  
>  	xdp_act = bpf_prog_run_xdp(xdp_prog, &xdp);
>  	rcu_read_unlock();
> diff --git a/drivers/net/ethernet/socionext/netsec.c b/drivers/net/ethernet/socionext/netsec.c
> index 945ca9517bf9..80bb1a6612b1 100644
> --- a/drivers/net/ethernet/socionext/netsec.c
> +++ b/drivers/net/ethernet/socionext/netsec.c
> @@ -1015,10 +1015,9 @@ static int netsec_process_rx(struct netsec_priv *priv, int budget)
>  					dma_dir);
>  		prefetch(desc->addr);
>  
> -		xdp.data_hard_start = desc->addr;
> -		xdp.data = desc->addr + NETSEC_RXBUF_HEADROOM;
> +		xdp_prepare_buff(&xdp, desc->addr, NETSEC_RXBUF_HEADROOM,
> +				 pkt_len);
>  		xdp_set_data_meta_invalid(&xdp);
> -		xdp.data_end = xdp.data + pkt_len;
>  
>  		if (xdp_prog) {
>  			xdp_result = netsec_run_xdp(priv, xdp_prog, &xdp);
> diff --git a/drivers/net/ethernet/ti/cpsw.c b/drivers/net/ethernet/ti/cpsw.c
> index 78a923391828..c08fd6a6be9b 100644
> --- a/drivers/net/ethernet/ti/cpsw.c
> +++ b/drivers/net/ethernet/ti/cpsw.c
> @@ -392,22 +392,17 @@ static void cpsw_rx_handler(void *token, int len, int status)
>  	}
>  
>  	if (priv->xdp_prog) {
> -		xdp_init_buff(&xdp, PAGE_SIZE, &priv->xdp_rxq[ch]);
> +		int headroom = CPSW_HEADROOM, size = len;
>  
> +		xdp_init_buff(&xdp, PAGE_SIZE, &priv->xdp_rxq[ch]);
>  		if (status & CPDMA_RX_VLAN_ENCAP) {
> -			xdp.data = pa + CPSW_HEADROOM +
> -				   CPSW_RX_VLAN_ENCAP_HDR_SIZE;
> -			xdp.data_end = xdp.data + len -
> -				       CPSW_RX_VLAN_ENCAP_HDR_SIZE;
> -		} else {
> -			xdp.data = pa + CPSW_HEADROOM;
> -			xdp.data_end = xdp.data + len;
> +			headroom += CPSW_RX_VLAN_ENCAP_HDR_SIZE;
> +			size -= CPSW_RX_VLAN_ENCAP_HDR_SIZE;
>  		}
>  
> +		xdp_prepare_buff(&xdp, pa, headroom, size);
>  		xdp_set_data_meta_invalid(&xdp);
>  
> -		xdp.data_hard_start = pa;
> -
>  		port = priv->emac_port + cpsw->data.dual_emac;
>  		ret = cpsw_run_xdp(priv, ch, &xdp, page, port);
>  		if (ret != CPSW_XDP_PASS)
> diff --git a/drivers/net/ethernet/ti/cpsw_new.c b/drivers/net/ethernet/ti/cpsw_new.c
> index 1b3385ec9645..c74c997d1cf2 100644
> --- a/drivers/net/ethernet/ti/cpsw_new.c
> +++ b/drivers/net/ethernet/ti/cpsw_new.c
> @@ -335,22 +335,17 @@ static void cpsw_rx_handler(void *token, int len, int status)
>  	}
>  
>  	if (priv->xdp_prog) {
> -		xdp_init_buff(&xdp, PAGE_SIZE, &priv->xdp_rxq[ch]);
> +		int headroom = CPSW_HEADROOM, size = len;
>  
> +		xdp_init_buff(&xdp, PAGE_SIZE, &priv->xdp_rxq[ch]);
>  		if (status & CPDMA_RX_VLAN_ENCAP) {
> -			xdp.data = pa + CPSW_HEADROOM +
> -				   CPSW_RX_VLAN_ENCAP_HDR_SIZE;
> -			xdp.data_end = xdp.data + len -
> -				       CPSW_RX_VLAN_ENCAP_HDR_SIZE;
> -		} else {
> -			xdp.data = pa + CPSW_HEADROOM;
> -			xdp.data_end = xdp.data + len;
> +			headroom += CPSW_RX_VLAN_ENCAP_HDR_SIZE;
> +			size -= CPSW_RX_VLAN_ENCAP_HDR_SIZE;
>  		}
>  
> +		xdp_prepare_buff(&xdp, pa, headroom, size);
>  		xdp_set_data_meta_invalid(&xdp);
>  
> -		xdp.data_hard_start = pa;
> -
>  		ret = cpsw_run_xdp(priv, ch, &xdp, page, priv->emac_port);
>  		if (ret != CPSW_XDP_PASS)
>  			goto requeue;
> diff --git a/drivers/net/hyperv/netvsc_bpf.c b/drivers/net/hyperv/netvsc_bpf.c
> index 14a7ee4c6899..93c202d6aff5 100644
> --- a/drivers/net/hyperv/netvsc_bpf.c
> +++ b/drivers/net/hyperv/netvsc_bpf.c
> @@ -45,10 +45,8 @@ u32 netvsc_run_xdp(struct net_device *ndev, struct netvsc_channel *nvchan,
>  	}
>  
>  	xdp_init_buff(xdp, PAGE_SIZE, &nvchan->xdp_rxq);
> -	xdp->data_hard_start = page_address(page);
> -	xdp->data = xdp->data_hard_start + NETVSC_XDP_HDRM;
> +	xdp_prepare_buff(xdp, page_address(page), NETVSC_XDP_HDRM, len);
>  	xdp_set_data_meta_invalid(xdp);
> -	xdp->data_end = xdp->data + len;
>  
>  	memcpy(xdp->data, data, len);
>  
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index a82f7823d428..c7cbd058b345 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1600,10 +1600,8 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
>  		u32 act;
>  
>  		xdp_init_buff(&xdp, buflen, &tfile->xdp_rxq);
> -		xdp.data_hard_start = buf;
> -		xdp.data = buf + pad;
> +		xdp_prepare_buff(&xdp, buf, pad, len);
>  		xdp_set_data_meta_invalid(&xdp);
> -		xdp.data_end = xdp.data + len;
>  
>  		act = bpf_prog_run_xdp(xdp_prog, &xdp);
>  		if (act == XDP_REDIRECT || act == XDP_TX) {
> diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> index 25f3601fb6dd..30a7f2ad39c3 100644
> --- a/drivers/net/veth.c
> +++ b/drivers/net/veth.c
> @@ -710,11 +710,7 @@ static struct sk_buff *veth_xdp_rcv_skb(struct veth_rq *rq,
>  		skb = nskb;
>  	}
>  
> -	xdp.data_hard_start = skb->head;
> -	xdp.data = skb_mac_header(skb);
> -	xdp.data_end = xdp.data + pktlen;
> -	xdp.data_meta = xdp.data;
> -
> +	xdp_prepare_buff(&xdp, skb->head, skb->mac_header, pktlen);
>  	/* SKB "head" area always have tailroom for skb_shared_info */
>  	frame_sz = (void *)skb_end_pointer(skb) - xdp.data_hard_start;
>  	frame_sz += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index a22ce87bcd9c..e57b2d452cbc 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -690,10 +690,8 @@ static struct sk_buff *receive_small(struct net_device *dev,
>  		}
>  
>  		xdp_init_buff(&xdp, buflen, &rq->xdp_rxq);
> -		xdp.data_hard_start = buf + VIRTNET_RX_PAD + vi->hdr_len;
> -		xdp.data = xdp.data_hard_start + xdp_headroom;
> -		xdp.data_end = xdp.data + len;
> -		xdp.data_meta = xdp.data;
> +		xdp_prepare_buff(&xdp, buf + VIRTNET_RX_PAD + vi->hdr_len,
> +				 xdp_headroom, len);
>  		orig_data = xdp.data;
>  		act = bpf_prog_run_xdp(xdp_prog, &xdp);
>  		stats->xdp_packets++;
> @@ -859,10 +857,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>  		 */
>  		data = page_address(xdp_page) + offset;
>  		xdp_init_buff(&xdp, frame_sz - vi->hdr_len, &rq->xdp_rxq);
> -		xdp.data_hard_start = data - VIRTIO_XDP_HEADROOM + vi->hdr_len;
> -		xdp.data = data + vi->hdr_len;
> -		xdp.data_end = xdp.data + (len - vi->hdr_len);
> -		xdp.data_meta = xdp.data;
> +		xdp_prepare_buff(&xdp, data - VIRTIO_XDP_HEADROOM + vi->hdr_len,
> +				 VIRTIO_XDP_HEADROOM, len - vi->hdr_len);
>  
>  		act = bpf_prog_run_xdp(xdp_prog, &xdp);
>  		stats->xdp_packets++;
> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
> index 329397c60d84..61d3f5f8b7f3 100644
> --- a/drivers/net/xen-netfront.c
> +++ b/drivers/net/xen-netfront.c
> @@ -866,10 +866,8 @@ static u32 xennet_run_xdp(struct netfront_queue *queue, struct page *pdata,
>  
>  	xdp_init_buff(xdp, XEN_PAGE_SIZE - XDP_PACKET_HEADROOM,
>  		      &queue->xdp_rxq);
> -	xdp->data_hard_start = page_address(pdata);
> -	xdp->data = xdp->data_hard_start + XDP_PACKET_HEADROOM;
> +	xdp_prepare_buff(xdp, page_address(pdata), XDP_PACKET_HEADROOM, len);
>  	xdp_set_data_meta_invalid(xdp);
> -	xdp->data_end = xdp->data + len;
>  
>  	act = bpf_prog_run_xdp(prog, xdp);
>  	switch (act) {
> diff --git a/include/net/xdp.h b/include/net/xdp.h
> index 3fb3a9aa1b71..66d8a4b317a3 100644
> --- a/include/net/xdp.h
> +++ b/include/net/xdp.h
> @@ -83,6 +83,18 @@ xdp_init_buff(struct xdp_buff *xdp, u32 frame_sz, struct xdp_rxq_info *rxq)
>  	xdp->rxq = rxq;
>  }
>  
> +static inline void
> +xdp_prepare_buff(struct xdp_buff *xdp, unsigned char *hard_start,
> +		 int headroom, int data_len)
> +{
> +	unsigned char *data = hard_start + headroom;
> +
> +	xdp->data_hard_start = hard_start;
> +	xdp->data = data;
> +	xdp->data_end = data + data_len;
> +	xdp->data_meta = data;
> +}
> +
>  /* Reserve memory area at end-of data area.
>   *
>   * This macro reserves tailroom in the XDP buffer by limiting the
> diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
> index a8fa5a9e4137..fe5a80d396e3 100644
> --- a/net/bpf/test_run.c
> +++ b/net/bpf/test_run.c
> @@ -636,10 +636,7 @@ int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
>  	if (IS_ERR(data))
>  		return PTR_ERR(data);
>  
> -	xdp.data_hard_start = data;
> -	xdp.data = data + headroom;
> -	xdp.data_meta = xdp.data;
> -	xdp.data_end = xdp.data + size;
> +	xdp_prepare_buff(&xdp, data, headroom, size);
>  
>  	rxqueue = __netif_get_rx_queue(current->nsproxy->net_ns->loopback_dev, 0);
>  	xdp_init_buff(&xdp, headroom + max_data_sz + tailroom,
> diff --git a/net/core/dev.c b/net/core/dev.c
> index bac56afcf6bc..2997177876cc 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -4592,7 +4592,7 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
>  	__be16 orig_eth_type;
>  	struct ethhdr *eth;
>  	bool orig_bcast;
> -	int hlen, off;
> +	int off;
>  
>  	/* Reinjected packets coming from act_mirred or similar should
>  	 * not get XDP generic processing.
> @@ -4624,11 +4624,9 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
>  	 * header.
>  	 */
>  	mac_len = skb->data - skb_mac_header(skb);
> -	hlen = skb_headlen(skb) + mac_len;
> -	xdp->data = skb->data - mac_len;
> -	xdp->data_meta = xdp->data;
> -	xdp->data_end = xdp->data + hlen;
> -	xdp->data_hard_start = skb->data - skb_headroom(skb);
> +	xdp_prepare_buff(xdp, skb->data - skb_headroom(skb),
> +			 skb_headroom(skb) - mac_len,
> +			 skb_headlen(skb) + mac_len);
>  
>  	/* SKB "head" area always have tailroom for skb_shared_info */
>  	frame_sz = (void *)skb_end_pointer(skb) - xdp->data_hard_start;
> -- 
> 2.29.2
>