[dpdk-dev] [PATCH 1/4] Revert "net/mlx5: fix Rx queue count calculation"

[Maxime Leroy <maxime.leroy@6wind.com>]

This reverts commit d2d57605522d4a43be17e22e649e54033f6d8835.

This fix is uncorrect for at least two reasons.

First issue, when there are more than 8 CQEs to uncompress, the
computation done in this commit cannot work. Because the zip-ai
variable describes the current index inside the CQE8 array and thus is
limited from 0 to 7 included. So if we are decompressed the 9 packets,
ai is 0. So in this case, n is equals to cqe_cnt - 0.

Example with 11 packets we will have:
C | a | e0 | e1 | e2 | e3 | e4 | e5 | C | a | e0

c <-- CQE compressed
a <-- Array of minicqe
ex <-- emptry entry to store uncompressed CQE.

If the 9th packet is decompressed by the soft, n is equals to 9.
But with this commit, n is equals to 11 (i.e. 11 - 0).

Second issue is to count the next packet.

Example:

     packet 1                       |    packet 2
C | a | e0 | e1 | e2 | e3 | e4 | e5 | C | a | e0

There are 2 packets compressed in the first queue. For the first packet,
n is computed correctly.

But for the second, n is not computed properly. Because the zip context
is for the first packet. The  second packet is not yet decompressed, so
there are no context.

Signed-off-by: Maxime Leroy <maxime.leroy@6wind.com>
Signed-off-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>
---
 drivers/net/mlx5/mlx5_rxtx.c | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
index 844a1c63..4c566486 100644
--- a/drivers/net/mlx5/mlx5_rxtx.c
+++ b/drivers/net/mlx5/mlx5_rxtx.c
@@ -462,11 +462,19 @@ rx_queue_count(struct mlx5_rxq_data *rxq)
 {
 	struct rxq_zip *zip = &rxq->zip;
 	volatile struct mlx5_cqe *cqe;
-	unsigned int cq_ci = rxq->cq_ci;
 	const unsigned int cqe_n = (1 << rxq->cqe_n);
 	const unsigned int cqe_cnt = cqe_n - 1;
-	unsigned int used = 0;
+	unsigned int cq_ci;
+	unsigned int used;
 
+	/* if we are processing a compressed cqe */
+	if (zip->ai) {
+		used = zip->cqe_cnt - zip->ca;
+		cq_ci = zip->cq_ci;
+	} else {
+		used = 0;
+		cq_ci = rxq->cq_ci;
+	}
 	cqe = &(*rxq->cqes)[cq_ci & cqe_cnt];
 	while (check_cqe(cqe, cqe_n, cq_ci) != MLX5_CQE_STATUS_HW_OWN) {
 		int8_t op_own;
@@ -474,17 +482,14 @@ rx_queue_count(struct mlx5_rxq_data *rxq)
 
 		op_own = cqe->op_own;
 		if (MLX5_CQE_FORMAT(op_own) == MLX5_COMPRESSED)
-			if (unlikely(zip->ai))
-				n = zip->cqe_cnt - zip->ai;
-			else
-				n = rte_be_to_cpu_32(cqe->byte_cnt);
+			n = rte_be_to_cpu_32(cqe->byte_cnt);
 		else
 			n = 1;
 		cq_ci += n;
 		used += n;
 		cqe = &(*rxq->cqes)[cq_ci & cqe_cnt];
 	}
-	used = RTE_MIN(used, cqe_n);
+	used = RTE_MIN(used, (1U << rxq->elts_n) - 1);
 	return used;
 }
 
@@ -507,12 +512,11 @@ mlx5_rx_descriptor_status(void *rx_queue, uint16_t offset)
 			container_of(rxq, struct mlx5_rxq_ctrl, rxq);
 	struct rte_eth_dev *dev = ETH_DEV(rxq_ctrl->priv);
 
-	if (dev->rx_pkt_burst == NULL ||
-	    dev->rx_pkt_burst == removed_rx_burst) {
+	if (dev->rx_pkt_burst != mlx5_rx_burst) {
 		rte_errno = ENOTSUP;
 		return -rte_errno;
 	}
-	if (offset >= (1 << rxq->cqe_n)) {
+	if (offset >= (1 << rxq->elts_n)) {
 		rte_errno = EINVAL;
 		return -rte_errno;
 	}
@@ -642,8 +646,7 @@ mlx5_rx_queue_count(struct rte_eth_dev *dev, uint16_t rx_queue_id)
 	struct mlx5_priv *priv = dev->data->dev_private;
 	struct mlx5_rxq_data *rxq;
 
-	if (dev->rx_pkt_burst == NULL ||
-	    dev->rx_pkt_burst == removed_rx_burst) {
+	if (dev->rx_pkt_burst != mlx5_rx_burst) {
 		rte_errno = ENOTSUP;
 		return -rte_errno;
 	}
-- 
2.27.0