Subject: Re: [PATCH iwl-next v7 4/5] igb: Add AF_XDP zero-copy Rx support

From: Kurt Kanzenbach <[email-masked]>
Date: Mon, 07 Oct 2024 15:45:47 +0200

Hi Maciej,

On Mon Oct 07 2024, Maciej Fijalkowski wrote:
> On Mon, Oct 07, 2024 at 02:31:26PM +0200, Kurt Kanzenbach wrote:
>> From: Sriram Yagnaraman <[email-masked]>
>> 
>> Add support for AF_XDP zero-copy receive path.
>> 
>> When AF_XDP zero-copy is enabled, the rx buffers are allocated from the
>> xsk buff pool using igb_alloc_rx_buffers_zc().
>> 
>> Use xsk_pool_get_rx_frame_size() to set SRRCTL rx buf size when zero-copy
>> is enabled.
>> 
>> Signed-off-by: Sriram Yagnaraman <[email-masked]>
>> [Kurt: Port to v6.10 and provide napi_id for xdp_rxq_info_reg(),
>>        RCT, remove NETDEV_XDP_ACT_XSK_ZEROCOPY, update NTC handling,
>>        move stats update and xdp finalize to common functions,
>>        READ_ONCE() xsk_pool, likelyfy for XDP_REDIRECT case]
>> Signed-off-by: Kurt Kanzenbach <[email-masked]>
>
> Hi Kurt,
>
> Sorry but still have comments :< see below.

No worries :)

>
>> ---
>>  drivers/net/ethernet/intel/igb/igb.h      |   8 +
>>  drivers/net/ethernet/intel/igb/igb_main.c | 132 +++++++++----
>>  drivers/net/ethernet/intel/igb/igb_xsk.c  | 296 +++++++++++++++++++++++++++++-
>>  3 files changed, 398 insertions(+), 38 deletions(-)
>> 
>> diff --git a/drivers/net/ethernet/intel/igb/igb.h b/drivers/net/ethernet/intel/igb/igb.h
>> index c30d6f9708f8..ea3977b313fc 100644
>> --- a/drivers/net/ethernet/intel/igb/igb.h
>> +++ b/drivers/net/ethernet/intel/igb/igb.h
>> @@ -88,6 +88,7 @@ struct igb_adapter;
>>  #define IGB_XDP_CONSUMED	BIT(0)
>>  #define IGB_XDP_TX		BIT(1)
>>  #define IGB_XDP_REDIR		BIT(2)
>> +#define IGB_XDP_EXIT		BIT(3)
>>  
>>  struct vf_data_storage {
>>  	unsigned char vf_mac_addresses[ETH_ALEN];
>> @@ -740,6 +741,9 @@ void igb_clean_tx_ring(struct igb_ring *tx_ring);
>>  void igb_clean_rx_ring(struct igb_ring *rx_ring);
>>  void igb_configure_tx_ring(struct igb_adapter *, struct igb_ring *);
>>  void igb_configure_rx_ring(struct igb_adapter *, struct igb_ring *);
>> +void igb_finalize_xdp(struct igb_adapter *adapter, unsigned int status);
>> +void igb_update_rx_stats(struct igb_q_vector *q_vector, unsigned int packets,
>> +			 unsigned int bytes);
>>  void igb_setup_tctl(struct igb_adapter *);
>>  void igb_setup_rctl(struct igb_adapter *);
>>  void igb_setup_srrctl(struct igb_adapter *, struct igb_ring *);
>> @@ -850,6 +854,10 @@ struct xsk_buff_pool *igb_xsk_pool(struct igb_adapter *adapter,
>>  int igb_xsk_pool_setup(struct igb_adapter *adapter,
>>  		       struct xsk_buff_pool *pool,
>>  		       u16 qid);
>> +bool igb_alloc_rx_buffers_zc(struct igb_ring *rx_ring, u16 count);
>> +void igb_clean_rx_ring_zc(struct igb_ring *rx_ring);
>> +int igb_clean_rx_irq_zc(struct igb_q_vector *q_vector,
>> +			struct xsk_buff_pool *xsk_pool, const int budget);
>>  int igb_xsk_wakeup(struct net_device *dev, u32 qid, u32 flags);
>>  
>>  #endif /* _IGB_H_ */
>> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
>> index bdba5c5861be..449ee794b3c9 100644
>> --- a/drivers/net/ethernet/intel/igb/igb_main.c
>> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
>> @@ -472,12 +472,17 @@ static void igb_dump(struct igb_adapter *adapter)
>>  
>>  		for (i = 0; i < rx_ring->count; i++) {
>>  			const char *next_desc;
>> -			struct igb_rx_buffer *buffer_info;
>> -			buffer_info = &rx_ring->rx_buffer_info[i];
>> +			dma_addr_t dma = (dma_addr_t)0;
>> +			struct igb_rx_buffer *buffer_info = NULL;
>>  			rx_desc = IGB_RX_DESC(rx_ring, i);
>>  			u0 = (struct my_u0 *)rx_desc;
>>  			staterr = le32_to_cpu(rx_desc->wb.upper.status_error);
>>  
>> +			if (!rx_ring->xsk_pool) {
>> +				buffer_info = &rx_ring->rx_buffer_info[i];
>> +				dma = buffer_info->dma;
>> +			}
>> +
>>  			if (i == rx_ring->next_to_use)
>>  				next_desc = " NTU";
>>  			else if (i == rx_ring->next_to_clean)
>> @@ -497,11 +502,11 @@ static void igb_dump(struct igb_adapter *adapter)
>>  					"R  ", i,
>>  					le64_to_cpu(u0->a),
>>  					le64_to_cpu(u0->b),
>> -					(u64)buffer_info->dma,
>> +					(u64)dma,
>>  					next_desc);
>>  
>>  				if (netif_msg_pktdata(adapter) &&
>> -				    buffer_info->dma && buffer_info->page) {
>> +				    buffer_info && dma && buffer_info->page) {
>>  					print_hex_dump(KERN_INFO, "",
>>  					  DUMP_PREFIX_ADDRESS,
>>  					  16, 1,
>> @@ -1983,7 +1988,10 @@ static void igb_configure(struct igb_adapter *adapter)
>>  	 */
>>  	for (i = 0; i < adapter->num_rx_queues; i++) {
>>  		struct igb_ring *ring = adapter->rx_ring[i];
>> -		igb_alloc_rx_buffers(ring, igb_desc_unused(ring));
>> +		if (ring->xsk_pool)
>> +			igb_alloc_rx_buffers_zc(ring, igb_desc_unused(ring));
>> +		else
>> +			igb_alloc_rx_buffers(ring, igb_desc_unused(ring));
>>  	}
>>  }
>>  
>> @@ -4405,7 +4413,8 @@ int igb_setup_rx_resources(struct igb_ring *rx_ring)
>>  	if (xdp_rxq_info_is_reg(&rx_ring->xdp_rxq))
>>  		xdp_rxq_info_unreg(&rx_ring->xdp_rxq);
>>  	res = xdp_rxq_info_reg(&rx_ring->xdp_rxq, rx_ring->netdev,
>> -			       rx_ring->queue_index, 0);
>> +			       rx_ring->queue_index,
>> +			       rx_ring->q_vector->napi.napi_id);
>>  	if (res < 0) {
>>  		dev_err(dev, "Failed to register xdp_rxq index %u\n",
>>  			rx_ring->queue_index);
>> @@ -4701,12 +4710,17 @@ void igb_setup_srrctl(struct igb_adapter *adapter, struct igb_ring *ring)
>>  	struct e1000_hw *hw = &adapter->hw;
>>  	int reg_idx = ring->reg_idx;
>>  	u32 srrctl = 0;
>> +	u32 buf_size;
>>  
>> -	srrctl = IGB_RX_HDR_LEN << E1000_SRRCTL_BSIZEHDRSIZE_SHIFT;
>> -	if (ring_uses_large_buffer(ring))
>> -		srrctl |= IGB_RXBUFFER_3072 >> E1000_SRRCTL_BSIZEPKT_SHIFT;
>> +	if (ring->xsk_pool)
>> +		buf_size = xsk_pool_get_rx_frame_size(ring->xsk_pool);
>> +	else if (ring_uses_large_buffer(ring))
>> +		buf_size = IGB_RXBUFFER_3072;
>>  	else
>> -		srrctl |= IGB_RXBUFFER_2048 >> E1000_SRRCTL_BSIZEPKT_SHIFT;
>> +		buf_size = IGB_RXBUFFER_2048;
>> +
>> +	srrctl = IGB_RX_HDR_LEN << E1000_SRRCTL_BSIZEHDRSIZE_SHIFT;
>> +	srrctl |= buf_size >> E1000_SRRCTL_BSIZEPKT_SHIFT;
>>  	srrctl |= E1000_SRRCTL_DESCTYPE_ADV_ONEBUF;
>>  	if (hw->mac.type >= e1000_82580)
>>  		srrctl |= E1000_SRRCTL_TIMESTAMP;
>> @@ -4738,9 +4752,17 @@ void igb_configure_rx_ring(struct igb_adapter *adapter,
>>  	u32 rxdctl = 0;
>>  
>>  	xdp_rxq_info_unreg_mem_model(&ring->xdp_rxq);
>> -	WARN_ON(xdp_rxq_info_reg_mem_model(&ring->xdp_rxq,
>> -					   MEM_TYPE_PAGE_SHARED, NULL));
>>  	WRITE_ONCE(ring->xsk_pool, igb_xsk_pool(adapter, ring));
>> +	if (ring->xsk_pool) {
>> +		WARN_ON(xdp_rxq_info_reg_mem_model(&ring->xdp_rxq,
>> +						   MEM_TYPE_XSK_BUFF_POOL,
>> +						   NULL));
>> +		xsk_pool_set_rxq_info(ring->xsk_pool, &ring->xdp_rxq);
>> +	} else {
>> +		WARN_ON(xdp_rxq_info_reg_mem_model(&ring->xdp_rxq,
>> +						   MEM_TYPE_PAGE_SHARED,
>> +						   NULL));
>> +	}
>>  
>>  	/* disable the queue */
>>  	wr32(E1000_RXDCTL(reg_idx), 0);
>> @@ -4767,9 +4789,12 @@ void igb_configure_rx_ring(struct igb_adapter *adapter,
>>  	rxdctl |= IGB_RX_HTHRESH << 8;
>>  	rxdctl |= IGB_RX_WTHRESH << 16;
>>  
>> -	/* initialize rx_buffer_info */
>> -	memset(ring->rx_buffer_info, 0,
>> -	       sizeof(struct igb_rx_buffer) * ring->count);
>> +	if (ring->xsk_pool)
>> +		memset(ring->rx_buffer_info_zc, 0,
>> +		       sizeof(*ring->rx_buffer_info_zc) * ring->count);
>> +	else
>> +		memset(ring->rx_buffer_info, 0,
>> +		       sizeof(*ring->rx_buffer_info) * ring->count);
>>  
>>  	/* initialize Rx descriptor 0 */
>>  	rx_desc = IGB_RX_DESC(ring, 0);
>> @@ -4957,8 +4982,13 @@ void igb_free_rx_resources(struct igb_ring *rx_ring)
>>  
>>  	rx_ring->xdp_prog = NULL;
>>  	xdp_rxq_info_unreg(&rx_ring->xdp_rxq);
>> -	vfree(rx_ring->rx_buffer_info);
>> -	rx_ring->rx_buffer_info = NULL;
>> +	if (rx_ring->xsk_pool) {
>> +		vfree(rx_ring->rx_buffer_info_zc);
>> +		rx_ring->rx_buffer_info_zc = NULL;
>> +	} else {
>> +		vfree(rx_ring->rx_buffer_info);
>> +		rx_ring->rx_buffer_info = NULL;
>> +	}
>>  
>>  	/* if not set, then don't free */
>>  	if (!rx_ring->desc)
>> @@ -4996,6 +5026,11 @@ void igb_clean_rx_ring(struct igb_ring *rx_ring)
>>  	dev_kfree_skb(rx_ring->skb);
>>  	rx_ring->skb = NULL;
>>  
>> +	if (rx_ring->xsk_pool) {
>> +		igb_clean_rx_ring_zc(rx_ring);
>> +		goto skip_for_xsk;
>> +	}
>> +
>>  	/* Free all the Rx ring sk_buffs */
>>  	while (i != rx_ring->next_to_alloc) {
>>  		struct igb_rx_buffer *buffer_info = &rx_ring->rx_buffer_info[i];
>> @@ -5023,6 +5058,7 @@ void igb_clean_rx_ring(struct igb_ring *rx_ring)
>>  			i = 0;
>>  	}
>>  
>> +skip_for_xsk:
>>  	rx_ring->next_to_alloc = 0;
>>  	rx_ring->next_to_clean = 0;
>>  	rx_ring->next_to_use = 0;
>> @@ -8177,6 +8213,7 @@ static int igb_poll(struct napi_struct *napi, int budget)
>>  	struct igb_q_vector *q_vector = container_of(napi,
>>  						     struct igb_q_vector,
>>  						     napi);
>> +	struct xsk_buff_pool *xsk_pool;
>>  	bool clean_complete = true;
>>  	int work_done = 0;
>>  
>> @@ -8188,7 +8225,12 @@ static int igb_poll(struct napi_struct *napi, int budget)
>>  		clean_complete = igb_clean_tx_irq(q_vector, budget);
>>  
>>  	if (q_vector->rx.ring) {
>> -		int cleaned = igb_clean_rx_irq(q_vector, budget);
>> +		int cleaned;
>> +
>> +		xsk_pool = READ_ONCE(q_vector->rx.ring->xsk_pool);
>> +		cleaned = xsk_pool ?
>> +			igb_clean_rx_irq_zc(q_vector, xsk_pool, budget) :
>> +			igb_clean_rx_irq(q_vector, budget);
>>  
>>  		work_done += cleaned;
>>  		if (cleaned >= budget)
>> @@ -8852,6 +8894,38 @@ static void igb_put_rx_buffer(struct igb_ring *rx_ring,
>>  	rx_buffer->page = NULL;
>>  }
>>  
>> +void igb_finalize_xdp(struct igb_adapter *adapter, unsigned int status)
>> +{
>> +	int cpu = smp_processor_id();
>> +	struct netdev_queue *nq;
>> +
>> +	if (status & IGB_XDP_REDIR)
>> +		xdp_do_flush();
>> +
>> +	if (status & IGB_XDP_TX) {
>> +		struct igb_ring *tx_ring = igb_xdp_tx_queue_mapping(adapter);
>> +
>> +		nq = txring_txq(tx_ring);
>> +		__netif_tx_lock(nq, cpu);
>> +		igb_xdp_ring_update_tail(tx_ring);
>> +		__netif_tx_unlock(nq);
>> +	}
>> +}
>> +
>> +void igb_update_rx_stats(struct igb_q_vector *q_vector, unsigned int packets,
>> +			 unsigned int bytes)
>> +{
>> +	struct igb_ring *ring = q_vector->rx.ring;
>> +
>> +	u64_stats_update_begin(&ring->rx_syncp);
>> +	ring->rx_stats.packets += packets;
>> +	ring->rx_stats.bytes += bytes;
>> +	u64_stats_update_end(&ring->rx_syncp);
>> +
>> +	q_vector->rx.total_packets += packets;
>> +	q_vector->rx.total_bytes += bytes;
>> +}
>> +
>>  static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
>>  {
>>  	unsigned int total_bytes = 0, total_packets = 0;
>> @@ -8859,9 +8933,7 @@ static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
>>  	struct igb_ring *rx_ring = q_vector->rx.ring;
>>  	u16 cleaned_count = igb_desc_unused(rx_ring);
>>  	struct sk_buff *skb = rx_ring->skb;
>> -	int cpu = smp_processor_id();
>>  	unsigned int xdp_xmit = 0;
>> -	struct netdev_queue *nq;
>>  	struct xdp_buff xdp;
>>  	u32 frame_sz = 0;
>>  	int rx_buf_pgcnt;
>> @@ -8983,24 +9055,10 @@ static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
>>  	/* place incomplete frames back on ring for completion */
>>  	rx_ring->skb = skb;
>>  
>> -	if (xdp_xmit & IGB_XDP_REDIR)
>> -		xdp_do_flush();
>> -
>> -	if (xdp_xmit & IGB_XDP_TX) {
>> -		struct igb_ring *tx_ring = igb_xdp_tx_queue_mapping(adapter);
>> -
>> -		nq = txring_txq(tx_ring);
>> -		__netif_tx_lock(nq, cpu);
>> -		igb_xdp_ring_update_tail(tx_ring);
>> -		__netif_tx_unlock(nq);
>> -	}
>> +	if (xdp_xmit)
>> +		igb_finalize_xdp(adapter, xdp_xmit);
>
> Nit: given you would be sending next revision, IMHO this is a candidate
> for a separate patch. Not a big deal but would reduce the noise in this
> one.

Yes, makes sense.

>
>>  
>> -	u64_stats_update_begin(&rx_ring->rx_syncp);
>> -	rx_ring->rx_stats.packets += total_packets;
>> -	rx_ring->rx_stats.bytes += total_bytes;
>> -	u64_stats_update_end(&rx_ring->rx_syncp);
>> -	q_vector->rx.total_packets += total_packets;
>> -	q_vector->rx.total_bytes += total_bytes;
>> +	igb_update_rx_stats(q_vector, total_packets, total_bytes);
>
> This also.
>
>>  
>>  	if (cleaned_count)
>>  		igb_alloc_rx_buffers(rx_ring, cleaned_count);
>> diff --git a/drivers/net/ethernet/intel/igb/igb_xsk.c b/drivers/net/ethernet/intel/igb/igb_xsk.c
>> index 7b632be3e7e3..9fd094a799fa 100644
>> --- a/drivers/net/ethernet/intel/igb/igb_xsk.c
>> +++ b/drivers/net/ethernet/intel/igb/igb_xsk.c
>> @@ -70,7 +70,10 @@ static void igb_txrx_ring_enable(struct igb_adapter *adapter, u16 qid)
>>  	 * at least 1 descriptor unused to make sure
>>  	 * next_to_use != next_to_clean
>>  	 */
>> -	igb_alloc_rx_buffers(rx_ring, igb_desc_unused(rx_ring));
>> +	if (rx_ring->xsk_pool)
>> +		igb_alloc_rx_buffers_zc(rx_ring, igb_desc_unused(rx_ring));
>> +	else
>> +		igb_alloc_rx_buffers(rx_ring, igb_desc_unused(rx_ring));
>>  
>>  	/* Rx/Tx share the same napi context. */
>>  	napi_enable(&rx_ring->q_vector->napi);
>> @@ -169,6 +172,297 @@ int igb_xsk_pool_setup(struct igb_adapter *adapter,
>>  		igb_xsk_pool_disable(adapter, qid);
>>  }
>>  
>> +static u16 igb_fill_rx_descs(struct xsk_buff_pool *pool, struct xdp_buff **xdp,
>> +			     union e1000_adv_rx_desc *rx_desc, u16 count)
>> +{
>> +	dma_addr_t dma;
>> +	u16 buffs;
>> +	int i;
>> +
>> +	/* nothing to do */
>> +	if (!count)
>> +		return 0;
>> +
>> +	buffs = xsk_buff_alloc_batch(pool, xdp, count);
>> +	for (i = 0; i < buffs; i++) {
>> +		dma = xsk_buff_xdp_get_dma(*xdp);
>> +		rx_desc->read.pkt_addr = cpu_to_le64(dma);
>> +		rx_desc->wb.upper.length = 0;
>> +
>> +		rx_desc++;
>> +		xdp++;
>> +	}
>> +
>> +	return buffs;
>> +}
>> +
>> +bool igb_alloc_rx_buffers_zc(struct igb_ring *rx_ring, u16 count)
>> +{
>> +	u32 nb_buffs_extra = 0, nb_buffs = 0;
>> +	union e1000_adv_rx_desc *rx_desc;
>> +	u16 ntu = rx_ring->next_to_use;
>> +	u16 total_count = count;
>> +	struct xdp_buff **xdp;
>> +
>> +	rx_desc = IGB_RX_DESC(rx_ring, ntu);
>> +	xdp = &rx_ring->rx_buffer_info_zc[ntu];
>> +
>> +	if (ntu + count >= rx_ring->count) {
>> +		nb_buffs_extra = igb_fill_rx_descs(rx_ring->xsk_pool, xdp,
>> +						   rx_desc,
>> +						   rx_ring->count - ntu);
>
> Ehh wanted to ack this finally, but I believe that here you need to work
> on the pool pointer that was READ_ONCE() in igb_poll() in hot path and
> in igb_configure() pass rx_ring->xsk_pool as an argument.

Good catch, thanks!

Thanks,
Kurt