[dpdk-stable] patch 'net/mlx5: fix external buffer pool registration for Rx queue' has been queued to stable release 20.11.2

[Xueming Li]

Hi,

FYI, your patch has been queued to stable release 20.11.2

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 05/12/21. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://github.com/steevenlee/dpdk

This queued commit can be viewed at:
https://github.com/steevenlee/dpdk/commit/23b584d6cc854fad62237b03899e494adc6526d5

Thanks.

Xueming Li <xuemingl at nvidia.com>

---
>From 23b584d6cc854fad62237b03899e494adc6526d5 Mon Sep 17 00:00:00 2001
From: Viacheslav Ovsiienko <viacheslavo at nvidia.com>
Date: Fri, 12 Feb 2021 13:06:30 +0200
Subject: [PATCH] net/mlx5: fix external buffer pool registration for Rx queue
Cc: Luca Boccassi <bluca at debian.org>

[ upstream commit a9ae33fbbc2d8d51542abf71d0a73887c17f39b5 ]

On Rx queue creation the mlx5 PMD registers the data buffers of the
specified pools for DMA operations. It scans the mem_list of the pools
and creates the MRs (DMA related NIC objects) for the chunks found.
If the pool is created with rte_pktmbuf_pool_create_extbuf() and
refers to the external attached buffers (whose are in the area of
application responsibility and it should explicitly register the
data buffer memory for DMA with rte_dev_dma_map() call) the chunks
contain the mbuf structures only, w/o any built-in data buffers.
Hence, DMA with mlx5 NIC never happens to this area and there is
no need to create MRs for these ones.

The extra not needed MRs were created for the pools with external
buffers causing MR cache load and performance was slightly affected.
The patch checks the mbuf pool type and skips MR creation for the
pools with external buffers.

Fixes: bdb8e5b1ea7b ("net/mlx5: allow allocated mbuf with external buffer")

Signed-off-by: Viacheslav Ovsiienko <viacheslavo at nvidia.com>
Acked-by: Matan Azrad <matan at nvidia.com>
---
 drivers/net/mlx5/mlx5_mr.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/net/mlx5/mlx5_mr.c b/drivers/net/mlx5/mlx5_mr.c
index 8b20ee3f83..da4e91fc24 100644
--- a/drivers/net/mlx5/mlx5_mr.c
+++ b/drivers/net/mlx5/mlx5_mr.c
@@ -535,7 +535,18 @@ mlx5_mr_update_mp(struct rte_eth_dev *dev, struct mlx5_mr_ctrl *mr_ctrl,
 		.mr_ctrl = mr_ctrl,
 		.ret = 0,
 	};
+	uint32_t flags = rte_pktmbuf_priv_flags(mp);
 
+	if (flags & RTE_PKTMBUF_POOL_F_PINNED_EXT_BUF) {
+		/*
+		 * The pinned external buffer should be registered for DMA
+		 * operations by application. The mem_list of the pool contains
+		 * the list of chunks with mbuf structures w/o built-in data
+		 * buffers and DMA actually does not happen there, no need
+		 * to create MR for these chunks.
+		 */
+		return 0;
+	}
 	DRV_LOG(DEBUG, "Port %u Rx queue registering mp %s "
 		       "having %u chunks.", dev->data->port_id,
 		       mp->name, mp->nb_mem_chunks);
-- 
2.25.1

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2021-05-10 23:59:26.943978500 +0800
+++ 0009-net-mlx5-fix-external-buffer-pool-registration-for-R.patch	2021-05-10 23:59:26.310000000 +0800
@@ -1 +1 @@
-From a9ae33fbbc2d8d51542abf71d0a73887c17f39b5 Mon Sep 17 00:00:00 2001
+From 23b584d6cc854fad62237b03899e494adc6526d5 Mon Sep 17 00:00:00 2001
@@ -4,0 +5,3 @@
+Cc: Luca Boccassi <bluca at debian.org>
+
+[ upstream commit a9ae33fbbc2d8d51542abf71d0a73887c17f39b5 ]
@@ -23 +25,0 @@
-Cc: stable at dpdk.org