Date:   Fri, 13 Nov 2020 13:30:41 +0000
From:   Camelia Alexandra Groza <camelia.groza@....com>
To:     Saeed Mahameed <saeed@...nel.org>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "brouer@...hat.com" <brouer@...hat.com>,
        "davem@...emloft.net" <davem@...emloft.net>
CC:     "Madalin Bucur (OSS)" <madalin.bucur@....nxp.com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH net-next 2/7] dpaa_eth: add basic XDP support

> -----Original Message-----
> From: Saeed Mahameed <saeed@...nel.org>
> Sent: Thursday, November 12, 2020 22:41
> To: Camelia Alexandra Groza <camelia.groza@....com>; kuba@...nel.org;
> brouer@...hat.com; davem@...emloft.net
> Cc: Madalin Bucur (OSS) <madalin.bucur@....nxp.com>; Ioana Ciornei
> <ioana.ciornei@....com>; netdev@...r.kernel.org
> Subject: Re: [PATCH net-next 2/7] dpaa_eth: add basic XDP support
> 
> On Thu, 2020-11-12 at 20:10 +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.
> >
> > Signed-off-by: Camelia Groza <camelia.groza@....com>
> > ---
> >  drivers/net/ethernet/freescale/dpaa/dpaa_eth.c | 148
> > ++++++++++++++++++++++---
> >  drivers/net/ethernet/freescale/dpaa/dpaa_eth.h |   2 +
> >  2 files changed, 134 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..d1d8a46 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);
> > +
> > +	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;
> > @@ -2364,10 +2415,11 @@ static enum qman_cb_dqrr_result
> > rx_default_dqrr(struct qman_portal *portal,
> >  	u32 fd_status, hash_offset;
> >  	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 +2475,58 @@ 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
> > +			dev_warn(net_dev->dev.parent,
> > "fman_port_get_tstamp failed!\n");
> 
> dev_warn per packet is a bad idea.. you might want to change this to
> WARN_ONCE() or a counter.

Sure, I'll change it to WARN_ONCE. This code is only moved higher up in the function call.

> > +	}
> > +
> > +	/* 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;
> > +	}
> > +
> 
> 
> I hope you keep this data avaialbe in the headroom buffer on
> extraction..
> Soon enough XDP programs will have the means to see the headroom meta
> data from the NIC.
> 
> https://zabiplane.groups.io/g/dev/message/56
> 
> Latest discussion on making NIC timestamp available to XDP programs.
> 
> https://www.spinics.net/lists/netdev/msg699281.html
> 

Yes, the data is still available in the headroom. Basically, it's positioned at xdp.data_hard_start. Since the XDP program might edit/overwrite it, I'm extracting it before calling the XDP program. The XDP program will be free to use it.

> > +	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 {
> > +		WARN_ONCE(priv->xdp_prog, "S/G frames not supported
> > under XDP\n");
> >  		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);
> >  	}
> >
> 

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