Subject: Re: [PATCH net-next v4 2/7] dpaa_eth: add basic XDP support

From: Maciej Fijalkowski <[email-masked]>
Date: Tue, 24 Nov 2020 14:51:17 +0100

On Mon, Nov 23, 2020 at 07:36:20PM +0200, Camelia Groza wrote:
> Implement the XDP_DROP and XDP_PASS actions.
> 
> Avoid draining and reconfiguring the buffer pool at each XDP
> setup/teardown by increasing the frame headroom and reserving
> XDP_PACKET_HEADROOM bytes from the start. Since we always reserve an
> entire page per buffer, this change only impacts Jumbo frame scenarios
> where the maximum linear frame size is reduced by 256 bytes. Multi
> buffer Scatter/Gather frames are now used instead in these scenarios.
> 
> Allow XDP programs to access the entire buffer.
> 
> The data in the received frame's headroom can be overwritten by the XDP
> program. Extract the relevant fields from the headroom while they are
> still available, before running the XDP program.
> 
> Since the headroom might be resized before the frame is passed up to the
> stack, remove the check for a fixed headroom value when building an skb.
> 
> Allow the meta data to be updated and pass the information up the stack.
> 
> Scatter/Gather frames are dropped when XDP is enabled.
> 
> Acked-by: Madalin Bucur <[email-masked]>
> Signed-off-by: Camelia Groza <[email-masked]>
> ---
> Changes in v2:
> - warn only once if extracting the timestamp from a received frame fails
> 
> Changes in v3:
> - drop received S/G frames when XDP is enabled
> 
> Changes in v4:
> - report a warning if the MTU is too hight for running XDP
> - report an error if opening the device fails in the XDP setup
> 
>  drivers/net/ethernet/freescale/dpaa/dpaa_eth.c | 166 ++++++++++++++++++++++---
>  drivers/net/ethernet/freescale/dpaa/dpaa_eth.h |   2 +
>  2 files changed, 152 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> index 88533a2..8acce62 100644
> --- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> +++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> @@ -53,6 +53,8 @@
>  #include <linux/dma-mapping.h>
>  #include <linux/sort.h>
>  #include <linux/phy_fixed.h>
> +#include <linux/bpf.h>
> +#include <linux/bpf_trace.h>
>  #include <soc/fsl/bman.h>
>  #include <soc/fsl/qman.h>
>  #include "fman.h"
> @@ -177,7 +179,7 @@
>  #define DPAA_HWA_SIZE (DPAA_PARSE_RESULTS_SIZE + DPAA_TIME_STAMP_SIZE \
>  		       + DPAA_HASH_RESULTS_SIZE)
>  #define DPAA_RX_PRIV_DATA_DEFAULT_SIZE (DPAA_TX_PRIV_DATA_SIZE + \
> -					dpaa_rx_extra_headroom)
> +					XDP_PACKET_HEADROOM - DPAA_HWA_SIZE)
>  #ifdef CONFIG_DPAA_ERRATUM_A050385
>  #define DPAA_RX_PRIV_DATA_A050385_SIZE (DPAA_A050385_ALIGN - DPAA_HWA_SIZE)
>  #define DPAA_RX_PRIV_DATA_SIZE (fman_has_errata_a050385() ? \
> @@ -1733,7 +1735,6 @@ static struct sk_buff *contig_fd_to_skb(const struct dpaa_priv *priv,
>  			SKB_DATA_ALIGN(sizeof(struct skb_shared_info)));
>  	if (WARN_ONCE(!skb, "Build skb failure on Rx\n"))
>  		goto free_buffer;
> -	WARN_ON(fd_off != priv->rx_headroom);
>  	skb_reserve(skb, fd_off);
>  	skb_put(skb, qm_fd_get_length(fd));
> 
> @@ -2349,12 +2350,62 @@ static enum qman_cb_dqrr_result rx_error_dqrr(struct qman_portal *portal,
>  	return qman_cb_dqrr_consume;
>  }
> 
> +static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd, void *vaddr,
> +			unsigned int *xdp_meta_len)
> +{
> +	ssize_t fd_off = qm_fd_get_offset(fd);
> +	struct bpf_prog *xdp_prog;
> +	struct xdp_buff xdp;
> +	u32 xdp_act;
> +
> +	rcu_read_lock();
> +
> +	xdp_prog = READ_ONCE(priv->xdp_prog);
> +	if (!xdp_prog) {
> +		rcu_read_unlock();
> +		return XDP_PASS;
> +	}
> +
> +	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.frame_sz = DPAA_BP_RAW_SIZE;
> +
> +	xdp_act = bpf_prog_run_xdp(xdp_prog, &xdp);
> +
> +	/* Update the length and the offset of the FD */
> +	qm_fd_set_contig(fd, xdp.data - vaddr, xdp.data_end - xdp.data);

Shouldn't you do this update based on xdp.data_meta, not xdp.data?

> +
> +	switch (xdp_act) {
> +	case XDP_PASS:
> +		*xdp_meta_len = xdp.data - xdp.data_meta;
> +		break;
> +	default:
> +		bpf_warn_invalid_xdp_action(xdp_act);
> +		fallthrough;
> +	case XDP_ABORTED:
> +		trace_xdp_exception(priv->net_dev, xdp_prog, xdp_act);
> +		fallthrough;
> +	case XDP_DROP:
> +		/* Free the buffer */
> +		free_pages((unsigned long)vaddr, 0);
> +		break;
> +	}
> +
> +	rcu_read_unlock();
> +
> +	return xdp_act;
> +}
> +
>  static enum qman_cb_dqrr_result rx_default_dqrr(struct qman_portal *portal,
>  						struct qman_fq *fq,
>  						const struct qm_dqrr_entry *dq,
>  						bool sched_napi)
>  {
> +	bool ts_valid = false, hash_valid = false;
>  	struct skb_shared_hwtstamps *shhwtstamps;
> +	unsigned int skb_len, xdp_meta_len = 0;
>  	struct rtnl_link_stats64 *percpu_stats;
>  	struct dpaa_percpu_priv *percpu_priv;
>  	const struct qm_fd *fd = &dq->fd;
> @@ -2362,12 +2413,14 @@ static enum qman_cb_dqrr_result rx_default_dqrr(struct qman_portal *portal,
>  	enum qm_fd_format fd_format;
>  	struct net_device *net_dev;
>  	u32 fd_status, hash_offset;
> +	struct qm_sg_entry *sgt;
>  	struct dpaa_bp *dpaa_bp;
>  	struct dpaa_priv *priv;
> -	unsigned int skb_len;
>  	struct sk_buff *skb;
>  	int *count_ptr;
> +	u32 xdp_act;
>  	void *vaddr;
> +	u32 hash;
>  	u64 ns;
> 
>  	fd_status = be32_to_cpu(fd->status);
> @@ -2423,35 +2476,67 @@ static enum qman_cb_dqrr_result rx_default_dqrr(struct qman_portal *portal,
>  	count_ptr = this_cpu_ptr(dpaa_bp->percpu_count);
>  	(*count_ptr)--;
> 
> -	if (likely(fd_format == qm_fd_contig))
> +	/* Extract the timestamp stored in the headroom before running XDP */
> +	if (priv->rx_tstamp) {
> +		if (!fman_port_get_tstamp(priv->mac_dev->port[RX], vaddr, &ns))
> +			ts_valid = true;
> +		else
> +			WARN_ONCE(1, "fman_port_get_tstamp failed!\n");
> +	}
> +
> +	/* Extract the hash stored in the headroom before running XDP */
> +	if (net_dev->features & NETIF_F_RXHASH && priv->keygen_in_use &&
> +	    !fman_port_get_hash_result_offset(priv->mac_dev->port[RX],
> +					      &hash_offset)) {
> +		hash = be32_to_cpu(*(u32 *)(vaddr + hash_offset));
> +		hash_valid = true;
> +	}
> +
> +	if (likely(fd_format == qm_fd_contig)) {
> +		xdp_act = dpaa_run_xdp(priv, (struct qm_fd *)fd, vaddr,
> +				       &xdp_meta_len);
> +		if (xdp_act != XDP_PASS) {
> +			percpu_stats->rx_packets++;
> +			percpu_stats->rx_bytes += qm_fd_get_length(fd);
> +			return qman_cb_dqrr_consume;
> +		}
>  		skb = contig_fd_to_skb(priv, fd);
> -	else
> +	} else {
> +		/* XDP doesn't support S/G frames. Return the fragments to the
> +		 * buffer pool and release the SGT.
> +		 */
> +		if (READ_ONCE(priv->xdp_prog)) {
> +			WARN_ONCE(1, "S/G frames not supported under XDP\n");
> +			sgt = vaddr + qm_fd_get_offset(fd);
> +			dpaa_release_sgt_members(sgt);
> +			free_pages((unsigned long)vaddr, 0);
> +			return qman_cb_dqrr_consume;
> +		}
>  		skb = sg_fd_to_skb(priv, fd);
> +	}
>  	if (!skb)
>  		return qman_cb_dqrr_consume;
> 
> -	if (priv->rx_tstamp) {
> +	if (xdp_meta_len)
> +		skb_metadata_set(skb, xdp_meta_len);
> +
> +	/* Set the previously extracted timestamp */
> +	if (ts_valid) {
>  		shhwtstamps = skb_hwtstamps(skb);
>  		memset(shhwtstamps, 0, sizeof(*shhwtstamps));
> -
> -		if (!fman_port_get_tstamp(priv->mac_dev->port[RX], vaddr, &ns))
> -			shhwtstamps->hwtstamp = ns_to_ktime(ns);
> -		else
> -			dev_warn(net_dev->dev.parent, "fman_port_get_tstamp failed!\n");
> +		shhwtstamps->hwtstamp = ns_to_ktime(ns);
>  	}
> 
>  	skb->protocol = eth_type_trans(skb, net_dev);
> 
> -	if (net_dev->features & NETIF_F_RXHASH && priv->keygen_in_use &&
> -	    !fman_port_get_hash_result_offset(priv->mac_dev->port[RX],
> -					      &hash_offset)) {
> +	/* Set the previously extracted hash */
> +	if (hash_valid) {
>  		enum pkt_hash_types type;
> 
>  		/* if L4 exists, it was used in the hash generation */
>  		type = be32_to_cpu(fd->status) & FM_FD_STAT_L4CV ?
>  			PKT_HASH_TYPE_L4 : PKT_HASH_TYPE_L3;
> -		skb_set_hash(skb, be32_to_cpu(*(u32 *)(vaddr + hash_offset)),
> -			     type);
> +		skb_set_hash(skb, hash, type);
>  	}
> 
>  	skb_len = skb->len;
> @@ -2671,6 +2756,54 @@ static int dpaa_eth_stop(struct net_device *net_dev)
>  	return err;
>  }
> 
> +static int dpaa_setup_xdp(struct net_device *net_dev, struct bpf_prog *prog)
> +{
> +	struct dpaa_priv *priv = netdev_priv(net_dev);
> +	struct bpf_prog *old_prog;
> +	int err, max_contig_data;
> +	bool up;
> +
> +	max_contig_data = priv->dpaa_bp->size - priv->rx_headroom;
> +
> +	/* S/G fragments are not supported in XDP-mode */
> +	if (prog &&
> +	    (net_dev->mtu + VLAN_ETH_HLEN + ETH_FCS_LEN > max_contig_data)) {
> +		dev_warn(net_dev->dev.parent,
> +			 "The maximum MTU for XDP is %d\n",
> +			 max_contig_data - VLAN_ETH_HLEN - ETH_FCS_LEN);
> +		return -EINVAL;
> +	}
> +
> +	up = netif_running(net_dev);
> +
> +	if (up)
> +		dpaa_eth_stop(net_dev);
> +
> +	old_prog = xchg(&priv->xdp_prog, prog);
> +	if (old_prog)
> +		bpf_prog_put(old_prog);
> +
> +	if (up) {
> +		err = dpaa_open(net_dev);
> +		if (err) {
> +			dev_err(net_dev->dev.parent, "dpaa_open() failed\n");
> +			return err;

So you decided not to take advantage of extack messages?

> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static int dpaa_xdp(struct net_device *net_dev, struct netdev_bpf *xdp)
> +{
> +	switch (xdp->command) {
> +	case XDP_SETUP_PROG:
> +		return dpaa_setup_xdp(net_dev, xdp->prog);
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
>  static int dpaa_ts_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
>  {
>  	struct dpaa_priv *priv = netdev_priv(dev);
> @@ -2737,6 +2870,7 @@ static int dpaa_ioctl(struct net_device *net_dev, struct ifreq *rq, int cmd)
>  	.ndo_set_rx_mode = dpaa_set_rx_mode,
>  	.ndo_do_ioctl = dpaa_ioctl,
>  	.ndo_setup_tc = dpaa_setup_tc,
> +	.ndo_bpf = dpaa_xdp,
>  };
> 
>  static int dpaa_napi_add(struct net_device *net_dev)
> diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.h b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.h
> index da30e5d..94e8613 100644
> --- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.h
> +++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.h
> @@ -196,6 +196,8 @@ struct dpaa_priv {
> 
>  	bool tx_tstamp; /* Tx timestamping enabled */
>  	bool rx_tstamp; /* Rx timestamping enabled */
> +
> +	struct bpf_prog *xdp_prog;
>  };
> 
>  /* from dpaa_ethtool.c */
> --
> 1.9.1
>