RE: [PATCH iwl-next,v1 1/1] igc: Add Tx hardware timestamp request for AF_XDP zero-copy packet

[Song, Yoong Siang]

On Tuesday, January 2, 2024 10:51 PM, Gomes, Vinicius <vinicius.gomes@xxxxxxxxx> wrote:
>Song Yoong Siang <yoong.siang.song@xxxxxxxxx> writes:
>
>> This patch adds support to per-packet Tx hardware timestamp request to
>> AF_XDP zero-copy packet via XDP Tx metadata framework. Please note that
>> user needs to enable Tx HW timestamp capability via igc_ioctl() with
>> SIOCSHWTSTAMP cmd before sending xsk Tx timestamp request.
>>
>> Same as implementation in RX timestamp XDP hints kfunc metadata, Timer 0
>> (adjustable clock) is used in xsk Tx hardware timestamp. i225/i226 have
>> four sets of timestamping registers. A pointer named "xsk_pending_ts"
>> is introduced to indicate the timestamping register is already occupied.
>> Furthermore, the mentioned pointer also being used to hold the transmit
>> completion until the tx hardware timestamp is ready. This is because for
>> i225/i226, the timestamp notification comes some time after the transmit
>> completion event. The driver will retrigger hardware irq to clean the
>> packet after retrieve the tx hardware timestamp.
>>
>> Besides, a pointer named "xsk_meta" is added into igc_tx_timestamp_request
>> structure as a hook to the metadata location of the transmit packet. When
>> a Tx timestamp interrupt happens, the interrupt handler will copy the
>> value of Tx timestamp into metadata via xsk_tx_metadata_complete().
>>
>> This patch is tested with tools/testing/selftests/bpf/xdp_hw_metadata
>> on Intel ADL-S platform. Below are the test steps and results.
>>
>> Command on DUT:
>> sudo ./xdp_hw_metadata <interface name>
>> sudo hwstamp_ctl -i <interface name> -t 1 -r 1
>> sudo ./testptp -d /dev/ptp0 -s
>>
>> Command on Link Partner:
>> echo -n xdp | nc -u -q1 <destination IPv4 addr> 9091
>>
>> Result:
>> xsk_ring_cons__peek: 1
>> 0x555b112ae958: rx_desc[6]->addr=86110 addr=86110 comp_addr=86110 EoP
>> rx_hash: 0xBFDEC36E with RSS type:0x1
>> HW RX-time:   1677762429190040955 (sec:1677762429.1900) delta to User RX-time
>sec:0.0001 (100.124 usec)
>> XDP RX-time:   1677762429190123163 (sec:1677762429.1901) delta to User RX-time
>sec:0.0000 (17.916 usec)
>> 0x555b112ae958: ping-pong with csum=404e (want c59e) csum_start=34
>csum_offset=6
>> 0x555b112ae958: complete tx idx=6 addr=6010
>> HW TX-complete-time:   1677762429190173323 (sec:1677762429.1902) delta to
>User TX-complete-time sec:0.0100 (10035.884 usec)
>> XDP RX-time:   1677762429190123163 (sec:1677762429.1901) delta to User TX-
>complete-time sec:0.0101 (10086.044 usec)
>> HW RX-time:   1677762429190040955 (sec:1677762429.1900) delta to HW TX-
>complete-time sec:0.0001 (132.368 usec)
>> 0x555b112ae958: complete rx idx=134 addr=86110
>>
>> Signed-off-by: Song Yoong Siang <yoong.siang.song@xxxxxxxxx>
>> ---
>>  drivers/net/ethernet/intel/igc/igc.h      | 15 ++++
>>  drivers/net/ethernet/intel/igc/igc_main.c | 88 ++++++++++++++++++++++-
>>  drivers/net/ethernet/intel/igc/igc_ptp.c  | 42 ++++++++---
>>  3 files changed, 134 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/intel/igc/igc.h b/drivers/net/ethernet/intel/igc/igc.h
>> index ac7c861e83a0..c831dde01662 100644
>> --- a/drivers/net/ethernet/intel/igc/igc.h
>> +++ b/drivers/net/ethernet/intel/igc/igc.h
>> @@ -79,6 +79,9 @@ struct igc_tx_timestamp_request {
>>  	u32 regl;              /* which TXSTMPL_{X} register should be used */
>>  	u32 regh;              /* which TXSTMPH_{X} register should be used */
>>  	u32 flags;             /* flags that should be added to the tx_buffer */
>> +	u8 xsk_queue_index;    /* Tx queue which requesting timestamp */
>> +	bool *xsk_pending_ts;  /* ref to tx ring for waiting timestamp event */
>
>I think that this indirection level to xsk_pending_ts in the tx_buffer is a
>bit too hard to follow. What I am thinking is keeping a pointer to
>tx_buffer here in igc_tx_timestamp_request, perhaps even in a union with
>the skb, and use a similar logic, if that pointer is valid the timestamp
>request is in use.
>
>Do you think it could work?
>
>(Perhaps we would need to also store the buffer type in the request, but
>I don't think that would be too weird)
>

Hi Vinicius,

Thanks for your comments. 
Keep a pointer to tx_buffer will work. I will make the pointer a union
with skb and use buffer_type to indicate whether skb or tx_buffer pointer should be use.
Is this sound better? 
 
>> +	struct xsk_tx_metadata_compl xsk_meta;	/* ref to xsk Tx metadata */
>>  };
>>
>>  struct igc_inline_rx_tstamps {
>> @@ -319,6 +322,9 @@ void igc_disable_tx_ring(struct igc_ring *ring);
>>  void igc_enable_tx_ring(struct igc_ring *ring);
>>  int igc_xsk_wakeup(struct net_device *dev, u32 queue_id, u32 flags);
>>
>> +/* AF_XDP TX metadata operations */
>> +extern const struct xsk_tx_metadata_ops igc_xsk_tx_metadata_ops;
>> +
>>  /* igc_dump declarations */
>>  void igc_rings_dump(struct igc_adapter *adapter);
>>  void igc_regs_dump(struct igc_adapter *adapter);
>> @@ -528,6 +534,7 @@ struct igc_tx_buffer {
>>  	DEFINE_DMA_UNMAP_ADDR(dma);
>>  	DEFINE_DMA_UNMAP_LEN(len);
>>  	u32 tx_flags;
>> +	bool xsk_pending_ts;
>>  };
>>
>>  struct igc_rx_buffer {
>> @@ -553,6 +560,14 @@ struct igc_xdp_buff {
>>  	struct igc_inline_rx_tstamps *rx_ts; /* data indication bit
>IGC_RXDADV_STAT_TSIP */
>>  };
>>
>> +struct igc_metadata_request {
>> +	struct xsk_tx_metadata *meta;
>> +	struct igc_adapter *adapter;
>
>If you have access to the tx_ring, you have access to the adapter, no
>need to have it here.

Sure, I will remove it and use
adapter = netdev_priv(tx_ring->netdev);

>
>> +	struct igc_ring *tx_ring;
>> +	bool *xsk_pending_ts;
>> +	u32 *cmd_type;
>
>I think this also would be clearer if here you had a pointer to the
>tx_buffer instead of only 'xsk_pending_ts'.
>

No problem. I will try to use tx_buffer pointer.

>I guess for cmd_type, no need for it to be a pointer, we can affort the
>extra copy.
>

I use pointer because we need to bring out the value of cmd_type and put it into tx_desc:
tx_desc->read.cmd_type_len = cpu_to_le32(cmd_type);
In this case, do you think it is make sense to keep cmd_type pointer?

>> +};
>> +
>>  struct igc_q_vector {
>>  	struct igc_adapter *adapter;    /* backlink */
>>  	void __iomem *itr_register;
>> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c
>b/drivers/net/ethernet/intel/igc/igc_main.c
>> index 61db1d3bfa0b..311c85f2d82d 100644
>> --- a/drivers/net/ethernet/intel/igc/igc_main.c
>> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
>> @@ -1553,7 +1553,7 @@ static bool igc_request_tx_tstamp(struct igc_adapter
>*adapter, struct sk_buff *s
>>  	for (i = 0; i < IGC_MAX_TX_TSTAMP_REGS; i++) {
>>  		struct igc_tx_timestamp_request *tstamp = &adapter->tx_tstamp[i];
>>
>> -		if (tstamp->skb)
>> +		if (tstamp->skb || tstamp->xsk_pending_ts)
>>  			continue;
>>
>>  		tstamp->skb = skb_get(skb);
>> @@ -2878,6 +2878,71 @@ static void igc_update_tx_stats(struct igc_q_vector
>*q_vector,
>>  	q_vector->tx.total_packets += packets;
>>  }
>>
>> +static void igc_xsk_request_timestamp(void *_priv)
>> +{
>> +	struct igc_metadata_request *meta_req = _priv;
>> +	struct igc_ring *tx_ring = meta_req->tx_ring;
>> +	struct igc_tx_timestamp_request *tstamp;
>> +	u32 *cmd_type = meta_req->cmd_type;
>> +	u32 tx_flags = IGC_TX_FLAGS_TSTAMP;
>> +	struct igc_adapter *adapter;
>> +	unsigned long lock_flags;
>> +	bool found = 0;
>> +	int i;
>> +
>> +	if (test_bit(IGC_RING_FLAG_TX_HWTSTAMP, &tx_ring->flags)) {
>> +		adapter = meta_req->adapter;
>> +
>> +		spin_lock_irqsave(&adapter->ptp_tx_lock, lock_flags);
>> +
>> +		for (i = 0; i < IGC_MAX_TX_TSTAMP_REGS; i++) {
>> +			tstamp = &adapter->tx_tstamp[i];
>> +
>> +			if (tstamp->skb || tstamp->xsk_pending_ts)
>> +				continue;
>> +
>> +			found = 1;
>
>nitpick: found is a bool, 'true' would read better.
>

You are right. I will change it accordingly.

>> +			break;
>> +		}
>> +
>> +		if (!found) {
>> +			adapter->tx_hwtstamp_skipped++;
>
>I think this is one those cases, that an early return or a goto would
>make the code easier to understand.
>

Ok, I will unlock the tx_ptp_lock here and make an early return.

>> +		} else {
>> +			tstamp->start = jiffies;
>> +			tstamp->xsk_queue_index = tx_ring->queue_index;
>> +
>> +			tstamp->xsk_pending_ts = meta_req->xsk_pending_ts;
>> +			*tstamp->xsk_pending_ts = true;
>> +
>> +			xsk_tx_metadata_to_compl(meta_req->meta,
>> +						 &tstamp->xsk_meta);
>> +
>> +			/* set timestamp bit based on the _TSTAMP(_X) bit. */
>> +			tx_flags |= tstamp->flags;
>> +			*cmd_type |= IGC_SET_FLAG(tx_flags,
>IGC_TX_FLAGS_TSTAMP,
>> +						  (IGC_ADVTXD_MAC_TSTAMP));
>> +			*cmd_type |= IGC_SET_FLAG(tx_flags,
>IGC_TX_FLAGS_TSTAMP_1,
>> +						  (IGC_ADVTXD_TSTAMP_REG_1));
>> +			*cmd_type |= IGC_SET_FLAG(tx_flags,
>IGC_TX_FLAGS_TSTAMP_2,
>> +						  (IGC_ADVTXD_TSTAMP_REG_2));
>> +			*cmd_type |= IGC_SET_FLAG(tx_flags,
>IGC_TX_FLAGS_TSTAMP_3,
>> +						  (IGC_ADVTXD_TSTAMP_REG_3));
>> +		}
>> +
>> +		spin_unlock_irqrestore(&adapter->ptp_tx_lock, lock_flags);
>> +	}
>> +}
>> +
>> +static u64 igc_xsk_fill_timestamp(void *_priv)
>> +{
>> +	return *(u64 *)_priv;
>> +}
>> +
>> +const struct xsk_tx_metadata_ops igc_xsk_tx_metadata_ops = {
>> +	.tmo_request_timestamp		= igc_xsk_request_timestamp,
>> +	.tmo_fill_timestamp		= igc_xsk_fill_timestamp,
>> +};
>> +
>>  static void igc_xdp_xmit_zc(struct igc_ring *ring)
>>  {
>>  	struct xsk_buff_pool *pool = ring->xsk_pool;
>> @@ -2899,6 +2964,8 @@ static void igc_xdp_xmit_zc(struct igc_ring *ring)
>>  	budget = igc_desc_unused(ring);
>>
>>  	while (xsk_tx_peek_desc(pool, &xdp_desc) && budget--) {
>> +		struct igc_metadata_request meta_req;
>> +		struct xsk_tx_metadata *meta = NULL;
>>  		u32 cmd_type, olinfo_status;
>>  		struct igc_tx_buffer *bi;
>>  		dma_addr_t dma;
>> @@ -2909,14 +2976,23 @@ static void igc_xdp_xmit_zc(struct igc_ring *ring)
>>  		olinfo_status = xdp_desc.len << IGC_ADVTXD_PAYLEN_SHIFT;
>>
>>  		dma = xsk_buff_raw_get_dma(pool, xdp_desc.addr);
>> +		meta = xsk_buff_get_metadata(pool, xdp_desc.addr);
>>  		xsk_buff_raw_dma_sync_for_device(pool, dma, xdp_desc.len);
>> +		bi = &ring->tx_buffer_info[ntu];
>> +
>> +		meta_req.adapter = netdev_priv(ring->netdev);
>> +		meta_req.tx_ring = ring;
>> +		meta_req.meta = meta;
>> +		meta_req.cmd_type = &cmd_type;
>> +		meta_req.xsk_pending_ts = &bi->xsk_pending_ts;
>> +		xsk_tx_metadata_request(meta, &igc_xsk_tx_metadata_ops,
>> +					&meta_req);
>>
>>  		tx_desc = IGC_TX_DESC(ring, ntu);
>>  		tx_desc->read.cmd_type_len = cpu_to_le32(cmd_type);
>>  		tx_desc->read.olinfo_status = cpu_to_le32(olinfo_status);
>>  		tx_desc->read.buffer_addr = cpu_to_le64(dma);
>>
>> -		bi = &ring->tx_buffer_info[ntu];
>>  		bi->type = IGC_TX_BUFFER_TYPE_XSK;
>>  		bi->protocol = 0;
>>  		bi->bytecount = xdp_desc.len;
>> @@ -2979,6 +3055,13 @@ static bool igc_clean_tx_irq(struct igc_q_vector
>*q_vector, int napi_budget)
>>  		if (!(eop_desc->wb.status & cpu_to_le32(IGC_TXD_STAT_DD)))
>>  			break;
>>
>> +		/* Hold the completions while there's a pending tx hardware
>> +		 * timestamp request from XDP Tx metadata.
>> +		 */
>> +		if (tx_buffer->type == IGC_TX_BUFFER_TYPE_XSK &&
>> +		    tx_buffer->xsk_pending_ts)
>> +			break;
>> +
>
>One scenario that I am worried about the completion part is when tstamp
>and non-tstamp packets are mixed in the same queue.
>
>For example, when the user sends a 1 tstamp packet followed by 1
>non-tstamp packet. Some other ratios might be interesting to test as
>well, 1:10 for example. I guess a simple bandwith test would be enough,
>comparing "non-tstamp only" with mixed traffic.
>
>Perhaps are some bad recollections from the past, but I remember that
>the hardware takes a bit of time when generating the timestamp
>interrupts, and so those types of mixed traffic would have wasted
>bandwidth.
>

Sure. I will try to perform some bandwidth test and share the result.
I guess I will try to use iperf. 
Any bandwidth test app that come into your mind? 

>>  		/* clear next_to_watch to prevent false hangs */
>>  		tx_buffer->next_to_watch = NULL;
>>
>> @@ -6819,6 +6902,7 @@ static int igc_probe(struct pci_dev *pdev,
>>
>>  	netdev->netdev_ops = &igc_netdev_ops;
>>  	netdev->xdp_metadata_ops = &igc_xdp_metadata_ops;
>> +	netdev->xsk_tx_metadata_ops = &igc_xsk_tx_metadata_ops;
>>  	igc_ethtool_set_ops(netdev);
>>  	netdev->watchdog_timeo = 5 * HZ;
>>
>> diff --git a/drivers/net/ethernet/intel/igc/igc_ptp.c
>b/drivers/net/ethernet/intel/igc/igc_ptp.c
>> index 885faaa7b9de..b722bca40309 100644
>> --- a/drivers/net/ethernet/intel/igc/igc_ptp.c
>> +++ b/drivers/net/ethernet/intel/igc/igc_ptp.c
>> @@ -11,6 +11,7 @@
>>  #include <linux/ktime.h>
>>  #include <linux/delay.h>
>>  #include <linux/iopoll.h>
>> +#include <net/xdp_sock.h>
>>
>>  #define INCVALUE_MASK		0x7fffffff
>>  #define ISGN			0x80000000
>> @@ -555,8 +556,15 @@ static void igc_ptp_clear_tx_tstamp(struct igc_adapter
>*adapter)
>>  	for (i = 0; i < IGC_MAX_TX_TSTAMP_REGS; i++) {
>>  		struct igc_tx_timestamp_request *tstamp = &adapter->tx_tstamp[i];
>>
>> -		dev_kfree_skb_any(tstamp->skb);
>> -		tstamp->skb = NULL;
>> +		if (tstamp->skb) {
>> +			dev_kfree_skb_any(tstamp->skb);
>> +			tstamp->skb = NULL;
>> +		} else if (tstamp->xsk_pending_ts) {
>> +			*tstamp->xsk_pending_ts = false;
>> +			tstamp->xsk_pending_ts = NULL;
>> +			igc_xsk_wakeup(adapter->netdev, tstamp->xsk_queue_index,
>> +				       0);
>> +		}
>>  	}
>>
>>  	spin_unlock_irqrestore(&adapter->ptp_tx_lock, flags);
>> @@ -657,8 +665,15 @@ static int igc_ptp_set_timestamp_mode(struct igc_adapter
>*adapter,
>>  static void igc_ptp_tx_timeout(struct igc_adapter *adapter,
>>  			       struct igc_tx_timestamp_request *tstamp)
>>  {
>> -	dev_kfree_skb_any(tstamp->skb);
>> -	tstamp->skb = NULL;
>> +	if (tstamp->skb) {
>> +		dev_kfree_skb_any(tstamp->skb);
>> +		tstamp->skb = NULL;
>> +	} else if (tstamp->xsk_pending_ts) {
>> +		*tstamp->xsk_pending_ts = false;
>> +		tstamp->xsk_pending_ts = NULL;
>> +		igc_xsk_wakeup(adapter->netdev, tstamp->xsk_queue_index, 0);
>> +	}
>> +
>>  	adapter->tx_hwtstamp_timeouts++;
>>
>>  	netdev_warn(adapter->netdev, "Tx timestamp timeout\n");
>> @@ -677,7 +692,7 @@ void igc_ptp_tx_hang(struct igc_adapter *adapter)
>>  	for (i = 0; i < IGC_MAX_TX_TSTAMP_REGS; i++) {
>>  		tstamp = &adapter->tx_tstamp[i];
>>
>> -		if (!tstamp->skb)
>> +		if (!tstamp->skb && !tstamp->xsk_pending_ts)
>>  			continue;
>>
>>  		if (time_is_after_jiffies(tstamp->start + IGC_PTP_TX_TIMEOUT))
>> @@ -705,7 +720,7 @@ static void igc_ptp_tx_reg_to_stamp(struct igc_adapter
>*adapter,
>>  	int adjust = 0;
>>
>>  	skb = tstamp->skb;
>> -	if (!skb)
>> +	if (!skb && !tstamp->xsk_pending_ts)
>>  		return;
>>
>>  	if (igc_ptp_systim_to_hwtstamp(adapter, &shhwtstamps, regval))
>> @@ -729,10 +744,19 @@ static void igc_ptp_tx_reg_to_stamp(struct igc_adapter
>*adapter,
>>  	shhwtstamps.hwtstamp =
>>  		ktime_add_ns(shhwtstamps.hwtstamp, adjust);
>>
>> -	tstamp->skb = NULL;
>> +	if (skb) {
>> +		tstamp->skb = NULL;
>> +		skb_tstamp_tx(skb, &shhwtstamps);
>> +		dev_kfree_skb_any(skb);
>> +	} else {
>> +		xsk_tx_metadata_complete(&tstamp->xsk_meta,
>> +					 &igc_xsk_tx_metadata_ops,
>> +					 &shhwtstamps.hwtstamp);
>>
>> -	skb_tstamp_tx(skb, &shhwtstamps);
>> -	dev_kfree_skb_any(skb);
>> +		*tstamp->xsk_pending_ts = false;
>> +		tstamp->xsk_pending_ts = NULL;
>> +		igc_xsk_wakeup(adapter->netdev, tstamp->xsk_queue_index, 0);
>> +	}
>>  }
>>
>>  /**
>> --
>> 2.34.1
>>
>
>--
>Vinicius

Thanks & Regards
Siang