libeth: support native XDP and register memory model

Expand libeth's Page Pool functionality by adding native XDP support.
This means picking the appropriate headroom and DMA direction.
Also, register all the created &page_pools as XDP memory models.
A driver then can call xdp_rxq_info_attach_page_pool() when registering
its RxQ info.

Signed-off-by: Alexander Lobakin <[e-mail]>
Signed-off-by: Tony Nguyen <[e-mail]>

drivers/net/ethernet/intel/libeth/rx.c

···
 static bool libeth_rx_page_pool_params(struct libeth_fq *fq,
 				       struct page_pool_params *pp)
 {
-	pp->offset = LIBETH_SKB_HEADROOM;
+	pp->offset = fq->xdp ? LIBETH_XDP_HEADROOM : LIBETH_SKB_HEADROOM;
 	/* HW-writeable / syncable length per one page */
 	pp->max_len = LIBETH_RX_PAGE_LEN(pp->offset);
 
···
 		.dev		= napi->dev->dev.parent,
 		.netdev		= napi->dev,
 		.napi		= napi,
-		.dma_dir	= DMA_FROM_DEVICE,
 	};
 	struct libeth_fqe *fqes;
 	struct page_pool *pool;
-	bool ret;
+	int ret;
+
+	pp.dma_dir = fq->xdp ? DMA_BIDIRECTIONAL : DMA_FROM_DEVICE;
 
 	if (!fq->hsplit)
 		ret = libeth_rx_page_pool_params(fq, &pp);
···
 		return PTR_ERR(pool);
 
 	fqes = kvcalloc_node(fq->count, sizeof(*fqes), GFP_KERNEL, fq->nid);
-	if (!fqes)
+	if (!fqes) {
+		ret = -ENOMEM;
 		goto err_buf;
+	}
+
+	ret = xdp_reg_page_pool(pool);
+	if (ret)
+		goto err_mem;
 
 	fq->fqes = fqes;
 	fq->pp = pool;
 
 	return 0;
 
+err_mem:
+	kvfree(fqes);
 err_buf:
 	page_pool_destroy(pool);
 
-	return -ENOMEM;
+	return ret;
 }
 EXPORT_SYMBOL_GPL(libeth_rx_fq_create);
 
···
  */
 void libeth_rx_fq_destroy(struct libeth_fq *fq)
 {
+	xdp_unreg_page_pool(fq->pp);
 	kvfree(fq->fqes);
 	page_pool_destroy(fq->pp);
 }

include/net/libeth/rx.h

···
 
 /* Space reserved in front of each frame */
 #define LIBETH_SKB_HEADROOM	(NET_SKB_PAD + NET_IP_ALIGN)
+#define LIBETH_XDP_HEADROOM	(ALIGN(XDP_PACKET_HEADROOM, NET_SKB_PAD) + \
+				 NET_IP_ALIGN)
 /* Maximum headroom for worst-case calculations */
-#define LIBETH_MAX_HEADROOM	LIBETH_SKB_HEADROOM
+#define LIBETH_MAX_HEADROOM	LIBETH_XDP_HEADROOM
 /* Link layer / L2 overhead: Ethernet, 2 VLAN tags (C + S), FCS */
 #define LIBETH_RX_LL_LEN	(ETH_HLEN + 2 * VLAN_HLEN + ETH_FCS_LEN)
 /* Maximum supported L2-L4 header length */
···
  * @count: number of descriptors/buffers the queue has
  * @type: type of the buffers this queue has
  * @hsplit: flag whether header split is enabled
+ * @xdp: flag indicating whether XDP is enabled
  * @buf_len: HW-writeable length per each buffer
  * @nid: ID of the closest NUMA node with memory
  */
···
 	/* Cold fields */
 	enum libeth_fqe_type	type:2;
 	bool			hsplit:1;
+	bool			xdp:1;
 
 	u32			buf_len;
 	int			nid;