mvneta: Add XDP frame size to driver

This marvell driver mvneta uses PAGE_SIZE frames, which makes it
really easy to convert.  Driver updates rxq and now frame_sz
once per NAPI call.

This driver takes advantage of page_pool PP_FLAG_DMA_SYNC_DEV that
can help reduce the number of cache-lines that need to be flushed
when doing DMA sync for_device. Due to xdp_adjust_tail can grow the
area accessible to the by the CPU (can possibly write into), then max
sync length *after* bpf_prog_run_xdp() needs to be taken into account.

For XDP_TX action the driver is smart and does DMA-sync. When growing
tail this is still safe, because page_pool have DMA-mapped the entire
page size.
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Cc: thomas.petazzoni@bootlin.com
Link: https://lore.kernel.org/bpf/158945335786.97035.12714388304493736747.stgit@firesoul

drivers/net/ethernet/marvell/mvneta.c

@@ -2148,12 +2148,17 @@ mvneta_run_xdp(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
 	       struct bpf_prog *prog, struct xdp_buff *xdp,
 	       struct mvneta_stats *stats)
 {
-	unsigned int len;
+	unsigned int len, sync;
+	struct page *page;
 	u32 ret, act;
 
 	len = xdp->data_end - xdp->data_hard_start - pp->rx_offset_correction;
 	act = bpf_prog_run_xdp(prog, xdp);
 
+	/* Due xdp_adjust_tail: DMA sync for_device cover max len CPU touch */
+	sync = xdp->data_end - xdp->data_hard_start - pp->rx_offset_correction;
+	sync = max(sync, len);
+
 	switch (act) {
 	case XDP_PASS:
 		stats->xdp_pass++;
@@ -2164,9 +2169,8 @@ mvneta_run_xdp(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
 		err = xdp_do_redirect(pp->dev, xdp, prog);
 		if (unlikely(err)) {
 			ret = MVNETA_XDP_DROPPED;
-			page_pool_put_page(rxq->page_pool,
-					   virt_to_head_page(xdp->data), len,
-					   true);
+			page = virt_to_head_page(xdp->data);
+			page_pool_put_page(rxq->page_pool, page, sync, true);
 		} else {
 			ret = MVNETA_XDP_REDIR;
 			stats->xdp_redirect++;
@@ -2175,10 +2179,10 @@ mvneta_run_xdp(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
 	}
 	case XDP_TX:
 		ret = mvneta_xdp_xmit_back(pp, xdp);
-		if (ret != MVNETA_XDP_TX)
-			page_pool_put_page(rxq->page_pool,
-					   virt_to_head_page(xdp->data), len,
-					   true);
+		if (ret != MVNETA_XDP_TX) {
+			page = virt_to_head_page(xdp->data);
+			page_pool_put_page(rxq->page_pool, page, sync, true);
+		}
 		break;
 	default:
 		bpf_warn_invalid_xdp_action(act);
@@ -2187,8 +2191,8 @@ mvneta_run_xdp(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
 		trace_xdp_exception(pp->dev, prog, act);
 		/* fall through */
 	case XDP_DROP:
-		page_pool_put_page(rxq->page_pool,
-				   virt_to_head_page(xdp->data), len, true);
+		page = virt_to_head_page(xdp->data);
+		page_pool_put_page(rxq->page_pool, page, sync, true);
 		ret = MVNETA_XDP_DROPPED;
 		stats->xdp_drop++;
 		break;
@@ -2320,6 +2324,7 @@ static int mvneta_rx_swbm(struct napi_struct *napi,
 	rcu_read_lock();
 	xdp_prog = READ_ONCE(pp->xdp_prog);
 	xdp_buf.rxq = &rxq->xdp_rxq;
+	xdp_buf.frame_sz = PAGE_SIZE;
 
 	/* Fairness NAPI loop */
 	while (rx_proc < budget && rx_proc < rx_todo) {