[net] igb: Fix XDP with PTP enabled

When using native XDP with the igb driver, the XDP frame data doesn't point to
the beginning of the packet. It's off by 16 bytes. Everything works as expected
with XDP skb mode.

Actually these 16 bytes are used to store the packet timestamps. Therefore, pull
the timestamp before executing any XDP operations and adjust all other code
accordingly. The igc driver does it like that as well.

Tested with Intel i210 card and AF_XDP sockets.

Fixes: 9cbc948b5a20 ("igb: add XDP support")
Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
---

Changes since RFC:

 * Removed unused return value definitions

Previous versions:

 * https://lkml.kernel.org/netdev/20210412101713.15161-1-kurt@linutronix.de/

drivers/net/ethernet/intel/igb/igb.h      |  3 +-
 drivers/net/ethernet/intel/igb/igb_main.c | 46 ++++++++++++-----------
 drivers/net/ethernet/intel/igb/igb_ptp.c  | 21 ++++-------
 3 files changed, 33 insertions(+), 37 deletions(-)

[...]
> @@ -8683,7 +8676,10 @@ static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
>  	while (likely(total_packets < budget)) {
>  		union e1000_adv_rx_desc *rx_desc;
>  		struct igb_rx_buffer *rx_buffer;
> +		ktime_t timestamp = 0;
> +		int pkt_offset = 0;
>  		unsigned int size;
> +		void *pktbuf;
>  
>  		/* return some buffers to hardware, one at a time is too slow */
>  		if (cleaned_count >= IGB_RX_BUFFER_WRITE) {
> @@ -8703,15 +8699,22 @@ static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
>  		dma_rmb();
>  
>  		rx_buffer = igb_get_rx_buffer(rx_ring, size, &rx_buf_pgcnt);
> +		pktbuf = page_address(rx_buffer->page) + rx_buffer->page_offset;
> +
> +		/* pull rx packet timestamp if available */
> +		if (igb_test_staterr(rx_desc, E1000_RXDADV_STAT_TSIP)) {
> +			timestamp = igb_ptp_rx_pktstamp(rx_ring->q_vector,
> +							pktbuf);
> +			pkt_offset += IGB_TS_HDR_LEN;
> +			size -= IGB_TS_HDR_LEN;
> +		}
>  
>  		/* retrieve a buffer from the ring */
>  		if (!skb) {
> -			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, true);
> +			xdp.data = pktbuf + pkt_offset;
> +			xdp.data_end = xdp.data + size;
> +			xdp.data_meta = xdp.data;
> +			xdp.data_hard_start = pktbuf - igb_rx_offset(rx_ring);

in order to keep it aligned with other xdp drivers, I guess you can do something like:

			unsigned char *hard_start = pktbuf - igb_rx_offset(rx_ring);
			unsigned int offset = pkt_offset + igb_rx_offset(rx_ring);

			xdp_prepare_buff(&xdp, hard_start, offset, size, true);

Probably the compiler will optimize it.

Regards,
Lorenzo

> When using native XDP with the igb driver, the XDP frame data doesn't point to
> the beginning of the packet. It's off by 16 bytes. Everything works as expected
> with XDP skb mode.
> 
> Actually these 16 bytes are used to store the packet timestamps. Therefore, pull
> the timestamp before executing any XDP operations and adjust all other code
> accordingly. The igc driver does it like that as well.
> 
> Tested with Intel i210 card and AF_XDP sockets.
> 
> Fixes: 9cbc948b5a20 ("igb: add XDP support")
> Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
> ---
> 
> Changes since RFC:
> 
>  * Removed unused return value definitions
> 
> Previous versions:
> 
>  * https://lkml.kernel.org/netdev/20210412101713.15161-1-kurt@linutronix.de/
> 
> drivers/net/ethernet/intel/igb/igb.h      |  3 +-
>  drivers/net/ethernet/intel/igb/igb_main.c | 46 ++++++++++++-----------
>  drivers/net/ethernet/intel/igb/igb_ptp.c  | 21 ++++-------
>  3 files changed, 33 insertions(+), 37 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/igb/igb.h b/drivers/net/ethernet/intel/igb/igb.h
> index 7bda8c5edea5..72cf967c1a00 100644
> --- a/drivers/net/ethernet/intel/igb/igb.h
> +++ b/drivers/net/ethernet/intel/igb/igb.h
> @@ -748,8 +748,7 @@ void igb_ptp_suspend(struct igb_adapter *adapter);
>  void igb_ptp_rx_hang(struct igb_adapter *adapter);
>  void igb_ptp_tx_hang(struct igb_adapter *adapter);
>  void igb_ptp_rx_rgtstamp(struct igb_q_vector *q_vector, struct sk_buff *skb);
> -int igb_ptp_rx_pktstamp(struct igb_q_vector *q_vector, void *va,
> -			struct sk_buff *skb);
> +ktime_t igb_ptp_rx_pktstamp(struct igb_q_vector *q_vector, void *va);
>  int igb_ptp_set_ts_config(struct net_device *netdev, struct ifreq *ifr);
>  int igb_ptp_get_ts_config(struct net_device *netdev, struct ifreq *ifr);
>  void igb_set_flag_queue_pairs(struct igb_adapter *, const u32);
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
> index a45cd2b416c8..4677b08d3270 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -8281,7 +8281,7 @@ static void igb_add_rx_frag(struct igb_ring *rx_ring,
>  static struct sk_buff *igb_construct_skb(struct igb_ring *rx_ring,
>  					 struct igb_rx_buffer *rx_buffer,
>  					 struct xdp_buff *xdp,
> -					 union e1000_adv_rx_desc *rx_desc)
> +					 ktime_t timestamp)
>  {
>  #if (PAGE_SIZE < 8192)
>  	unsigned int truesize = igb_rx_pg_size(rx_ring) / 2;
> @@ -8301,12 +8301,8 @@ static struct sk_buff *igb_construct_skb(struct igb_ring *rx_ring,
>  	if (unlikely(!skb))
>  		return NULL;
>  
> -	if (unlikely(igb_test_staterr(rx_desc, E1000_RXDADV_STAT_TSIP))) {
> -		if (!igb_ptp_rx_pktstamp(rx_ring->q_vector, xdp->data, skb)) {
> -			xdp->data += IGB_TS_HDR_LEN;
> -			size -= IGB_TS_HDR_LEN;
> -		}
> -	}
> +	if (timestamp)
> +		skb_hwtstamps(skb)->hwtstamp = timestamp;
>  
>  	/* Determine available headroom for copy */
>  	headlen = size;
> @@ -8337,7 +8333,7 @@ static struct sk_buff *igb_construct_skb(struct igb_ring *rx_ring,
>  static struct sk_buff *igb_build_skb(struct igb_ring *rx_ring,
>  				     struct igb_rx_buffer *rx_buffer,
>  				     struct xdp_buff *xdp,
> -				     union e1000_adv_rx_desc *rx_desc)
> +				     ktime_t timestamp)
>  {
>  #if (PAGE_SIZE < 8192)
>  	unsigned int truesize = igb_rx_pg_size(rx_ring) / 2;
> @@ -8364,11 +8360,8 @@ static struct sk_buff *igb_build_skb(struct igb_ring *rx_ring,
>  	if (metasize)
>  		skb_metadata_set(skb, metasize);
>  
> -	/* pull timestamp out of packet data */
> -	if (igb_test_staterr(rx_desc, E1000_RXDADV_STAT_TSIP)) {
> -		if (!igb_ptp_rx_pktstamp(rx_ring->q_vector, skb->data, skb))
> -			__skb_pull(skb, IGB_TS_HDR_LEN);
> -	}
> +	if (timestamp)
> +		skb_hwtstamps(skb)->hwtstamp = timestamp;
>  
>  	/* update buffer offset */
>  #if (PAGE_SIZE < 8192)

>  #if (PAGE_SIZE > 4096)
>  			/* At larger PAGE_SIZE, frame_sz depend on len size */
>  			xdp.frame_sz = igb_rx_frame_truesize(rx_ring, size);
> @@ -8733,10 +8736,11 @@ static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
>  		} else if (skb)
>  			igb_add_rx_frag(rx_ring, rx_buffer, skb, size);
>  		else if (ring_uses_build_skb(rx_ring))
> -			skb = igb_build_skb(rx_ring, rx_buffer, &xdp, rx_desc);
> +			skb = igb_build_skb(rx_ring, rx_buffer, &xdp,
> +					    timestamp);
>  		else
>  			skb = igb_construct_skb(rx_ring, rx_buffer,
> -						&xdp, rx_desc);
> +						&xdp, timestamp);
>  
>  		/* exit if we failed to retrieve a buffer */
>  		if (!skb) {
> diff --git a/drivers/net/ethernet/intel/igb/igb_ptp.c b/drivers/net/ethernet/intel/igb/igb_ptp.c
> index 86a576201f5f..8e23df7da641 100644
> --- a/drivers/net/ethernet/intel/igb/igb_ptp.c
> +++ b/drivers/net/ethernet/intel/igb/igb_ptp.c
> @@ -856,30 +856,26 @@ static void igb_ptp_tx_hwtstamp(struct igb_adapter *adapter)
>  	dev_kfree_skb_any(skb);
>  }
>  
> -#define IGB_RET_PTP_DISABLED 1
> -#define IGB_RET_PTP_INVALID 2
> -
>  /**
>   * igb_ptp_rx_pktstamp - retrieve Rx per packet timestamp
>   * @q_vector: Pointer to interrupt specific structure
>   * @va: Pointer to address containing Rx buffer
> - * @skb: Buffer containing timestamp and packet
>   *
>   * This function is meant to retrieve a timestamp from the first buffer of an
>   * incoming frame.  The value is stored in little endian format starting on
>   * byte 8
>   *
> - * Returns: 0 if success, nonzero if failure
> + * Returns: 0 on failure, timestamp on success
>   **/
> -int igb_ptp_rx_pktstamp(struct igb_q_vector *q_vector, void *va,
> -			struct sk_buff *skb)
> +ktime_t igb_ptp_rx_pktstamp(struct igb_q_vector *q_vector, void *va)
>  {
>  	struct igb_adapter *adapter = q_vector->adapter;
> +	struct skb_shared_hwtstamps ts;
>  	__le64 *regval = (__le64 *)va;
>  	int adjust = 0;
>  
>  	if (!(adapter->ptp_flags & IGB_PTP_ENABLED))
> -		return IGB_RET_PTP_DISABLED;
> +		return 0;
>  
>  	/* The timestamp is recorded in little endian format.
>  	 * DWORD: 0        1        2        3
> @@ -888,10 +884,9 @@ int igb_ptp_rx_pktstamp(struct igb_q_vector *q_vector, void *va,
>  
>  	/* check reserved dwords are zero, be/le doesn't matter for zero */
>  	if (regval[0])
> -		return IGB_RET_PTP_INVALID;
> +		return 0;
>  
> -	igb_ptp_systim_to_hwtstamp(adapter, skb_hwtstamps(skb),
> -				   le64_to_cpu(regval[1]));
> +	igb_ptp_systim_to_hwtstamp(adapter, &ts, le64_to_cpu(regval[1]));
>  
>  	/* adjust timestamp for the RX latency based on link speed */
>  	if (adapter->hw.mac.type == e1000_i210) {
> @@ -907,10 +902,8 @@ int igb_ptp_rx_pktstamp(struct igb_q_vector *q_vector, void *va,
>  			break;
>  		}
>  	}
> -	skb_hwtstamps(skb)->hwtstamp =
> -		ktime_sub_ns(skb_hwtstamps(skb)->hwtstamp, adjust);
>  
> -	return 0;
> +	return ktime_sub_ns(ts.hwtstamp, adjust);
>  }
>  
>  /**
> -- 
> 2.20.1
>

On Thu, 15 Apr 2021 11:21:45 +0200
Kurt Kanzenbach <kurt@linutronix.de> wrote:

> When using native XDP with the igb driver, the XDP frame data doesn't point to
> the beginning of the packet. It's off by 16 bytes. Everything works as expected
> with XDP skb mode.
> 
> Actually these 16 bytes are used to store the packet timestamps. Therefore, pull
> the timestamp before executing any XDP operations and adjust all other code
> accordingly. The igc driver does it like that as well.
> 
> Tested with Intel i210 card and AF_XDP sockets.

Doesn't the i210 card use the igc driver?
This change is for igb driver.


> Fixes: 9cbc948b5a20 ("igb: add XDP support")
> Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
> ---
[...]
> 
> drivers/net/ethernet/intel/igb/igb.h      |  3 +-
>  drivers/net/ethernet/intel/igb/igb_main.c | 46 ++++++++++++-----------
>  drivers/net/ethernet/intel/igb/igb_ptp.c  | 21 ++++-------
>  3 files changed, 33 insertions(+), 37 deletions(-)

> Doesn't the i210 card use the igc driver?
> This change is for igb driver.

The igb driver is used for the i210/i211, not igc.

On Thu Apr 15 2021, Jesper Dangaard Brouer wrote:
> I have a project involving i225+igc (using TSN).  And someone suggested
> that I also looked at i210 for TSN.  I've ordered hardware that have
> i210 on motherboard (and I will insert my i225 card) so I have a system
> with both chips for experimenting with TSN.  I guess, I would have
> discovered this eventually when I got the hardware.  Thanks for saving
> me from this mistake. Thanks!

Well, both cards are interesting for TSN. However, the i225 has some
advanced features in contrast to the i210. For instance, it supports
time aware scheduling (IEEE 802.1Qbv) in hardware through the Linux
TAPRIO interface.

Thanks,
Kurt