On Thu, Apr 08, 2021 at 02:50:55PM +0200, Lorenzo Bianconi wrote:

quoted

Update multi-buffer bit (mb) in xdp_buff to notify XDP/eBPF layer and
XDP remote drivers if this is a "non-linear" XDP buffer. Access
xdp_shared_info only if xdp_buff mb is set.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 drivers/net/ethernet/marvell/mvneta.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index a52e132fd2cf..94e29cce693a 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c

@@ -2041,12 +2041,16 @@ mvneta_xdp_put_buff(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
 {
 	int i;
 
+	if (likely(!xdp->mb))
+		goto out;
+

Is there any particular reason for this extra check?

xdp_sinfo->frags[] is initialized just if xdp->mb is set.

Regards,
Lorenzo

quoted

 	for (i = 0; i < xdp_sinfo->nr_frags; i++) {
 		skb_frag_t *frag = &xdp_sinfo->frags[i];
 
 		page_pool_put_full_page(rxq->page_pool,
 					xdp_get_frag_page(frag), true);
 	}
+out:
 	page_pool_put_page(rxq->page_pool, virt_to_head_page(xdp->data),
 			   sync_len, true);
 }

@@ -2246,7 +2250,6 @@ mvneta_swbm_rx_frame(struct mvneta_port *pp,
 {
 	unsigned char *data = page_address(page);
 	int data_len = -MVNETA_MH_SIZE, len;
-	struct xdp_shared_info *xdp_sinfo;
 	struct net_device *dev = pp->dev;
 	enum dma_data_direction dma_dir;
 

@@ -2270,9 +2273,6 @@ mvneta_swbm_rx_frame(struct mvneta_port *pp,
 	prefetch(data);
 	xdp_prepare_buff(xdp, data, pp->rx_offset_correction + MVNETA_MH_SIZE,
 			 data_len, false);
-
-	xdp_sinfo = xdp_get_shared_info_from_buff(xdp);
-	xdp_sinfo->nr_frags = 0;
 }
 
 static void

@@ -2307,12 +2307,18 @@ mvneta_swbm_add_rx_fragment(struct mvneta_port *pp,
 		xdp_set_frag_size(frag, data_len);
 		xdp_set_frag_page(frag, page);
 
+		if (!xdp->mb) {
+			xdp_sinfo->data_length = *size;
+			xdp->mb = 1;
+		}
 		/* last fragment */
 		if (len == *size) {
 			struct xdp_shared_info *sinfo;
 
 			sinfo = xdp_get_shared_info_from_buff(xdp);
 			sinfo->nr_frags = xdp_sinfo->nr_frags;
+			sinfo->data_length = xdp_sinfo->data_length;
+
 			memcpy(sinfo->frags, xdp_sinfo->frags,
 			       sinfo->nr_frags * sizeof(skb_frag_t));
 		}

@@ -2327,11 +2333,15 @@ mvneta_swbm_build_skb(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
 		      struct xdp_buff *xdp, u32 desc_status)
 {
 	struct xdp_shared_info *xdp_sinfo = xdp_get_shared_info_from_buff(xdp);
-	int i, num_frags = xdp_sinfo->nr_frags;
 	skb_frag_t frag_list[MAX_SKB_FRAGS];
+	int i, num_frags = 0;
 	struct sk_buff *skb;
 
-	memcpy(frag_list, xdp_sinfo->frags, sizeof(skb_frag_t) * num_frags);
+	if (unlikely(xdp->mb)) {
+		num_frags = xdp_sinfo->nr_frags;
+		memcpy(frag_list, xdp_sinfo->frags,
+		       sizeof(skb_frag_t) * num_frags);
+	}
 
 	skb = build_skb(xdp->data_hard_start, PAGE_SIZE);
 	if (!skb)

@@ -2343,6 +2353,9 @@ mvneta_swbm_build_skb(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
 	skb_put(skb, xdp->data_end - xdp->data);
 	mvneta_rx_csum(pp, desc_status, skb);
 
+	if (likely(!xdp->mb))
+		return skb;
+
 	for (i = 0; i < num_frags; i++) {
 		struct page *page = xdp_get_frag_page(&frag_list[i]);
 

@@ -2404,6 +2417,7 @@ static int mvneta_rx_swbm(struct napi_struct *napi,
 			frame_sz = size - ETH_FCS_LEN;
 			desc_status = rx_status;
 
+			xdp_buf.mb = 0;
 			mvneta_swbm_rx_frame(pp, rx_desc, rxq, &xdp_buf,
 					     &size, page);
 		} else {

-- 
2.30.2