[PATCH iwl-next 08/10] ixgbevf: add pseudo header split

[Larysa Zaremba]

From: Natalia Wochtman <natalia.wochtman@xxxxxxxxx>

Introduce pseudo header split support in the ixgbevf driver, specifically
targeting ixgbe_mac_82599_vf.

On older hardware (e.g. ixgbe_mac_82599_vf), RX DMA write size can only be
limited in 1K increments. This causes issues when attempting to fit
multiple packets per page, as a DMA write may overwrite the
headroom of the next packet.

To address this, introduce pseudo header split support, where the hardware
copies the full L2 header into a dedicated header buffer. This avoids the
need for HR/TR alignment and allows safe skb construction from the header
buffer without risking overwrites.

Given that once packet is too big to fit into a single page, the behaviour
is the same for all supported HW, use pseudo header split only for smaller
packets.

Signed-off-by: Natalia Wochtman <natalia.wochtman@xxxxxxxxx>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@xxxxxxxxx>
Co-developed-by: Larysa Zaremba <larysa.zaremba@xxxxxxxxx>
Signed-off-by: Larysa Zaremba <larysa.zaremba@xxxxxxxxx>
---
 drivers/net/ethernet/intel/ixgbevf/ixgbevf.h  |   8 +
 .../net/ethernet/intel/ixgbevf/ixgbevf_main.c | 178 +++++++++++++++---
 2 files changed, 161 insertions(+), 25 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbevf/ixgbevf.h b/drivers/net/ethernet/intel/ixgbevf/ixgbevf.h
index 61883b1e1f78..86b23f595d4c 100644
--- a/drivers/net/ethernet/intel/ixgbevf/ixgbevf.h
+++ b/drivers/net/ethernet/intel/ixgbevf/ixgbevf.h
@@ -90,6 +90,7 @@ struct ixgbevf_ring {
 		u32 truesize;		/* Rx buffer full size */
 		u32 pending;		/* Sent-not-completed descriptors */
 	};
+	u32 hdr_truesize;		/* Rx header buffer full size */
 	u16 count;			/* amount of descriptors */
 	u16 next_to_clean;
 	u32 next_to_use;
@@ -108,6 +109,8 @@ struct ixgbevf_ring {
 		struct ixgbevf_tx_queue_stats tx_stats;
 		struct ixgbevf_rx_queue_stats rx_stats;
 	};
+	struct libeth_fqe *hdr_fqes;
+	struct page_pool *hdr_pp;
 	struct xdp_rxq_info xdp_rxq;
 	u64 hw_csum_rx_error;
 	u8 __iomem *tail;
@@ -117,6 +120,7 @@ struct ixgbevf_ring {
 	 */
 	u16 reg_idx;
 	int queue_index; /* needed for multiqueue queue management */
+	u32 hdr_buf_len;
 	u32 rx_buf_len;
 	struct libeth_xdp_buff_stash xdp_stash;
 	unsigned int dma_size;		/* length in bytes */
@@ -152,6 +156,8 @@ struct ixgbevf_ring {
 
 #define IXGBEVF_RX_PAGE_LEN(hr)		(ALIGN_DOWN(LIBETH_RX_PAGE_LEN(hr), \
 					 IXGBE_SRRCTL_BSIZEPKT_STEP))
+#define IXGBEVF_RX_SRRCTL_BUF_SIZE(mtu)	(ALIGN((mtu) + LIBETH_RX_LL_LEN, \
+					       IXGBE_SRRCTL_BSIZEPKT_STEP))
 
 #define IXGBE_TX_FLAGS_CSUM		BIT(0)
 #define IXGBE_TX_FLAGS_VLAN		BIT(1)
@@ -350,6 +356,8 @@ enum ixbgevf_state_t {
 	__IXGBEVF_QUEUE_RESET_REQUESTED,
 };
 
+#define IXGBEVF_FLAG_HSPLIT	BIT(0)
+
 enum ixgbevf_boards {
 	board_82599_vf,
 	board_82599_vf_hv,
diff --git a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
index b0f34f097bf6..790e86135fbd 100644
--- a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
+++ b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
@@ -561,6 +561,12 @@ static void ixgbevf_alloc_rx_buffers(struct ixgbevf_ring *rx_ring,
 		.truesize	= rx_ring->truesize,
 		.count		= rx_ring->count,
 	};
+	const struct libeth_fq_fp hdr_fq = {
+		.pp		= rx_ring->hdr_pp,
+		.fqes		= rx_ring->hdr_fqes,
+		.truesize	= rx_ring->hdr_truesize,
+		.count		= rx_ring->count,
+	};
 	u16 ntu = rx_ring->next_to_use;
 
 	/* nothing to do or no valid netdev defined */
@@ -578,6 +584,12 @@ static void ixgbevf_alloc_rx_buffers(struct ixgbevf_ring *rx_ring,
 
 		rx_desc->read.pkt_addr = cpu_to_le64(addr);
 
+		if (hdr_fq.pp) {
+			addr = libeth_rx_alloc(&hdr_fq, ntu);
+			if (addr == DMA_MAPPING_ERROR)
+				return;
+		}
+
 		rx_desc++;
 		ntu++;
 		if (unlikely(ntu == fq.count)) {
@@ -820,6 +832,32 @@ LIBETH_XDP_DEFINE_FINALIZE(static ixgbevf_xdp_finalize_xdp_napi,
 			   ixgbevf_xdp_flush_tx, ixgbevf_xdp_rs_and_bump);
 LIBETH_XDP_DEFINE_END();
 
+static u32 ixgbevf_rx_hsplit_wa(const struct libeth_fqe *hdr,
+				struct libeth_fqe *buf, u32 data_len)
+{
+	u32 copy = data_len <= L1_CACHE_BYTES ? data_len : ETH_HLEN;
+	struct page *hdr_page, *buf_page;
+	const void *src;
+	void *dst;
+
+	if (unlikely(netmem_is_net_iov(buf->netmem)) ||
+	    !libeth_rx_sync_for_cpu(buf, copy))
+		return 0;
+
+	hdr_page = __netmem_to_page(hdr->netmem);
+	buf_page = __netmem_to_page(buf->netmem);
+
+	dst = page_address(hdr_page) + hdr->offset +
+	      pp_page_to_nmdesc(hdr_page)->pp->p.offset;
+	src = page_address(buf_page) + buf->offset +
+	      pp_page_to_nmdesc(buf_page)->pp->p.offset;
+
+	memcpy(dst, src, LARGEST_ALIGN(copy));
+	buf->offset += copy;
+
+	return copy;
+}
+
 static int ixgbevf_clean_rx_irq(struct ixgbevf_q_vector *q_vector,
 				struct ixgbevf_ring *rx_ring,
 				int budget)
@@ -859,6 +897,23 @@ static int ixgbevf_clean_rx_irq(struct ixgbevf_q_vector *q_vector,
 		rmb();
 
 		rx_buffer = &rx_ring->rx_fqes[rx_ring->next_to_clean];
+
+		if (unlikely(rx_ring->hdr_pp)) {
+			struct libeth_fqe *hdr_buff;
+			unsigned int hdr_size = 0;
+
+			hdr_buff = &rx_ring->hdr_fqes[rx_ring->next_to_clean];
+
+			if (!xdp->data) {
+				hdr_size = ixgbevf_rx_hsplit_wa(hdr_buff,
+								rx_buffer,
+								size);
+				size -= hdr_size ? : size;
+			}
+
+			libeth_xdp_process_buff(xdp, hdr_buff, hdr_size);
+		}
+
 		libeth_xdp_process_buff(xdp, rx_buffer, size);
 
 		cleaned_count++;
@@ -1598,6 +1653,90 @@ static void ixgbevf_setup_vfmrqc(struct ixgbevf_adapter *adapter)
 	IXGBE_WRITE_REG(hw, IXGBE_VFMRQC, vfmrqc);
 }
 
+static void ixgbevf_rx_destroy_pp(struct ixgbevf_ring *rx_ring)
+{
+	struct libeth_fq fq = {
+		.pp	= rx_ring->pp,
+		.fqes	= rx_ring->rx_fqes,
+	};
+
+	libeth_rx_fq_destroy(&fq);
+	rx_ring->rx_fqes = NULL;
+	rx_ring->pp = NULL;
+
+	if (!rx_ring->hdr_pp)
+		return;
+
+	fq = (struct libeth_fq) {
+		.pp	= rx_ring->hdr_pp,
+		.fqes	= rx_ring->hdr_fqes,
+	};
+
+	libeth_rx_fq_destroy(&fq);
+	rx_ring->hdr_fqes = NULL;
+	rx_ring->hdr_pp = NULL;
+}
+
+static int ixgbevf_rx_create_pp(struct ixgbevf_ring *rx_ring)
+{
+	u32 adapter_flags = rx_ring->q_vector->adapter->flags;
+	struct libeth_fq fq = {
+		.count		= rx_ring->count,
+		.nid		= NUMA_NO_NODE,
+		.type		= LIBETH_FQE_MTU,
+		.xdp		= !!rx_ring->xdp_prog,
+		.idx		= rx_ring->queue_index,
+		.buf_len	= IXGBEVF_RX_PAGE_LEN(rx_ring->xdp_prog ?
+						      LIBETH_XDP_HEADROOM :
+						      LIBETH_SKB_HEADROOM),
+	};
+	u32 frame_size;
+	int ret;
+
+	/* Some HW requires DMA write sizes to be aligned to 1K,
+	 * which warrants fake header split usage, but this is
+	 * not an issue if the frame size is at its maximum of 3K
+	 */
+	frame_size =
+		IXGBEVF_RX_SRRCTL_BUF_SIZE(READ_ONCE(rx_ring->netdev->mtu));
+	fq.hsplit = (adapter_flags & IXGBEVF_FLAG_HSPLIT) &&
+		    frame_size < fq.buf_len;
+	ret = libeth_rx_fq_create(&fq, &rx_ring->q_vector->napi);
+	if (ret)
+		return ret;
+
+	rx_ring->pp = fq.pp;
+	rx_ring->rx_fqes = fq.fqes;
+	rx_ring->truesize = fq.truesize;
+	rx_ring->rx_buf_len = fq.buf_len;
+
+	if (!fq.hsplit)
+		return 0;
+
+	fq = (struct libeth_fq) {
+		.count		= rx_ring->count,
+		.nid		= NUMA_NO_NODE,
+		.type		= LIBETH_FQE_HDR,
+		.xdp		= !!rx_ring->xdp_prog,
+		.idx		= rx_ring->queue_index,
+	};
+
+	ret = libeth_rx_fq_create(&fq, &rx_ring->q_vector->napi);
+	if (ret)
+		goto err;
+
+	rx_ring->hdr_pp = fq.pp;
+	rx_ring->hdr_fqes = fq.fqes;
+	rx_ring->hdr_truesize = fq.truesize;
+	rx_ring->hdr_buf_len = fq.buf_len;
+
+	return 0;
+
+err:
+	ixgbevf_rx_destroy_pp(rx_ring);
+	return ret;
+}
+
 static void ixgbevf_configure_rx_ring(struct ixgbevf_adapter *adapter,
 				      struct ixgbevf_ring *ring)
 {
@@ -2718,6 +2857,9 @@ static int ixgbevf_sw_init(struct ixgbevf_adapter *adapter)
 			goto out;
 	}
 
+	if (adapter->hw.mac.type == ixgbe_mac_82599_vf)
+		adapter->flags |= IXGBEVF_FLAG_HSPLIT;
+
 	/* assume legacy case in which PF would only give VF 2 queues */
 	hw->mac.max_tx_queues = 2;
 	hw->mac.max_rx_queues = 2;
@@ -3152,43 +3294,29 @@ static int ixgbevf_setup_all_tx_resources(struct ixgbevf_adapter *adapter)
 }
 
 /**
- * ixgbevf_setup_rx_resources - allocate Rx resources (Descriptors)
+ * ixgbevf_setup_rx_resources - allocate Rx resources
  * @adapter: board private structure
  * @rx_ring: Rx descriptor ring (for a specific queue) to setup
  *
- * Returns 0 on success, negative on failure
+ * Returns: 0 on success, negative on failure.
  **/
 int ixgbevf_setup_rx_resources(struct ixgbevf_adapter *adapter,
 			       struct ixgbevf_ring *rx_ring)
 {
-	struct libeth_fq fq = {
-		.count		= rx_ring->count,
-		.nid		= NUMA_NO_NODE,
-		.type		= LIBETH_FQE_MTU,
-		.xdp		= !!rx_ring->xdp_prog,
-		.idx		= rx_ring->queue_index,
-		.buf_len	= IXGBEVF_RX_PAGE_LEN(rx_ring->xdp_prog ?
-						      LIBETH_XDP_HEADROOM :
-						      LIBETH_SKB_HEADROOM),
-	};
 	int ret;
 
-	ret = libeth_rx_fq_create(&fq, &rx_ring->q_vector->napi);
+	ret = ixgbevf_rx_create_pp(rx_ring);
 	if (ret)
 		return ret;
 
-	rx_ring->pp = fq.pp;
-	rx_ring->rx_fqes = fq.fqes;
-	rx_ring->truesize = fq.truesize;
-	rx_ring->rx_buf_len = fq.buf_len;
-
 	u64_stats_init(&rx_ring->syncp);
 
 	/* Round up to nearest 4K */
 	rx_ring->dma_size = rx_ring->count * sizeof(union ixgbe_adv_rx_desc);
 	rx_ring->dma_size = ALIGN(rx_ring->dma_size, 4096);
 
-	rx_ring->desc = dma_alloc_coherent(fq.pp->p.dev, rx_ring->dma_size,
+	rx_ring->desc = dma_alloc_coherent(rx_ring->pp->p.dev,
+					   rx_ring->dma_size,
 					   &rx_ring->dma, GFP_KERNEL);
 
 	if (!rx_ring->desc)
@@ -3200,16 +3328,15 @@ int ixgbevf_setup_rx_resources(struct ixgbevf_adapter *adapter,
 	if (ret)
 		goto err;
 
-	xdp_rxq_info_attach_page_pool(&rx_ring->xdp_rxq, fq.pp);
+	xdp_rxq_info_attach_page_pool(&rx_ring->xdp_rxq, rx_ring->pp);
 
 	rx_ring->xdp_prog = adapter->xdp_prog;
 
 	return 0;
 err:
-	libeth_rx_fq_destroy(&fq);
-	rx_ring->rx_fqes = NULL;
-	rx_ring->pp = NULL;
+	ixgbevf_rx_destroy_pp(rx_ring);
 	dev_err(rx_ring->dev, "Unable to allocate memory for the Rx descriptor ring\n");
+
 	return ret;
 }
 
@@ -4138,10 +4265,11 @@ static int ixgbevf_xdp_setup(struct net_device *dev, struct bpf_prog *prog,
 	struct bpf_prog *old_prog;
 	bool requires_mbuf;
 
-	requires_mbuf = frame_size > IXGBEVF_RX_PAGE_LEN(LIBETH_XDP_HEADROOM);
+	requires_mbuf = frame_size > IXGBEVF_RX_PAGE_LEN(LIBETH_XDP_HEADROOM) ||
+			adapter->flags & IXGBEVF_FLAG_HSPLIT;
 	if (prog && !prog->aux->xdp_has_frags && requires_mbuf) {
 		NL_SET_ERR_MSG_MOD(extack,
-				   "Configured MTU requires non-linear frames and XDP prog does not support frags");
+				   "Configured MTU or HW limitations require non-linear frames and XDP prog does not support frags");
 		return -EOPNOTSUPP;
 	}
 
-- 
2.52.0