[PATCH] net/mlx5: add 128B padding of Rx completion entry

[Xing Zhang <zhangxing_neurs@163.com>]

From: "Xing Zhang zhangxing_neurs@163.com" <zhangxing_neurs@163.com>

When using Verbs flow engine("dv_flow_en"=0)and compile macro contain
HAVE_IBV_MLX5_MOD_CQE_128B_PAD, vendor cap lag is setted to
MLX5DV_CQ_INIT_ATTR_FLAGS_CQE_PAD.But if the device is not support the
capability, this will cause CQ creation failure.So use padded CQE when
system cache-line size is 128B and the device has the capability of
CQE padding. The patch that CQE padding device argument should
not be deleted.

Fixes: 4a7f979af28e ("net/mlx5: remove CQE padding device argument")
Cc: stable@dpdk.org

Signed-off-by: Xing Zhang <zhangxing_neurs@163.com>
---
 doc/guides/nics/mlx5.rst            | 19 ++++++++++++++++++-
 drivers/net/mlx5/linux/mlx5_os.c    |  5 +++++
 drivers/net/mlx5/linux/mlx5_verbs.c |  2 +-
 drivers/net/mlx5/mlx5.c             | 13 ++++++++++++-
 drivers/net/mlx5/mlx5.h             |  2 ++
 5 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst
index a0b9284..bd11e5e 100644
--- a/doc/guides/nics/mlx5.rst
+++ b/doc/guides/nics/mlx5.rst
@@ -14,7 +14,6 @@ ConnectX-6 Lx**, **Mellanox BlueField** and **Mellanox BlueField-2** families
 of 10/25/40/50/100/200 Gb/s adapters as well as their virtual functions (VF)
 in SR-IOV context.
 
-
 Design
 ------
 
@@ -580,6 +579,24 @@ for an additional list of options shared with other mlx5 drivers.
   - POWER9 and ARMv8 with ConnectX-4 Lx, ConnectX-5, ConnectX-6, ConnectX-6 Dx,
     ConnectX-6 Lx, BlueField and BlueField-2.
 
+- ``rxq_cqe_pad_en`` parameter [int]
+
+  A nonzero value enables 128B padding of CQE on RX side. The size of CQE
+  is aligned with the size of a cacheline of the core. If cacheline size is
+  128B, the CQE size is configured to be 128B even though the device writes
+  only 64B data on the cacheline. This is to avoid unnecessary cache
+  invalidation by device's two consecutive writes on to one cacheline.
+  However in some architecture, it is more beneficial to update entire
+  cacheline with padding the rest 64B rather than striding because
+  read-modify-write could drop performance a lot. On the other hand,
+  writing extra data will consume more PCIe bandwidth and could also drop
+  the maximum throughput. It is recommended to empirically set this
+  parameter. Disabled by default.
+
+  Supported on:
+
+  - CPU having 128B cacheline with ConnectX-5 and BlueField.
+
 - ``rxq_pkt_pad_en`` parameter [int]
 
   A nonzero value enables padding Rx packet to the size of cacheline on PCI
diff --git a/drivers/net/mlx5/linux/mlx5_os.c b/drivers/net/mlx5/linux/mlx5_os.c
index a821153..ef26d94 100644
--- a/drivers/net/mlx5/linux/mlx5_os.c
+++ b/drivers/net/mlx5/linux/mlx5_os.c
@@ -298,6 +298,11 @@ mlx5_os_capabilities_prepare(struct mlx5_dev_ctx_shared *sh)
 		DRV_LOG(DEBUG, "Device supports Multi-Packet RQ.");
 	}
 #endif
+#ifdef HAVE_IBV_MLX5_MOD_CQE_128B_PAD
+	/* Whether device supports 128B Rx CQE padding. */
+	sh->dev_cap.cqe_pad = RTE_CACHE_LINE_SIZE == 128 &&
+		(dv_attr.flags & MLX5DV_CONTEXT_FLAGS_CQE_128B_PAD);
+#endif
 #ifdef HAVE_IBV_DEVICE_TUNNEL_SUPPORT
 	if (dv_attr.comp_mask & MLX5DV_CONTEXT_MASK_TUNNEL_OFFLOADS) {
 		sh->dev_cap.tunnel_en = dv_attr.tunnel_offloads_caps &
diff --git a/drivers/net/mlx5/linux/mlx5_verbs.c b/drivers/net/mlx5/linux/mlx5_verbs.c
index b6ba21c..4ced94a 100644
--- a/drivers/net/mlx5/linux/mlx5_verbs.c
+++ b/drivers/net/mlx5/linux/mlx5_verbs.c
@@ -200,7 +200,7 @@ mlx5_rxq_ibv_cq_create(struct mlx5_rxq_priv *rxq)
 			priv->dev_data->port_id);
 	}
 #ifdef HAVE_IBV_MLX5_MOD_CQE_128B_PAD
-	if (RTE_CACHE_LINE_SIZE == 128) {
+	if (priv->config.cqe_pad) {
 		cq_attr.mlx5.comp_mask |= MLX5DV_CQ_INIT_ATTR_MASK_FLAGS;
 		cq_attr.mlx5.flags |= MLX5DV_CQ_INIT_ATTR_FLAGS_CQE_PAD;
 	}
diff --git a/drivers/net/mlx5/mlx5.c b/drivers/net/mlx5/mlx5.c
index 72b1e35..51c92b2 100644
--- a/drivers/net/mlx5/mlx5.c
+++ b/drivers/net/mlx5/mlx5.c
@@ -46,6 +46,9 @@
 /* Device parameter to enable RX completion queue compression. */
 #define MLX5_RXQ_CQE_COMP_EN "rxq_cqe_comp_en"
 
+/* Device parameter to enable RX completion entry padding to 128B. */
+#define MLX5_RXQ_CQE_PAD_EN "rxq_cqe_pad_en"
+
 /* Device parameter to enable padding Rx packet to cacheline size. */
 #define MLX5_RXQ_PKT_PAD_EN "rxq_pkt_pad_en"
 
@@ -2176,7 +2179,9 @@ mlx5_port_args_check_handler(const char *key, const char *val, void *opaque)
 		}
 		config->cqe_comp = !!tmp;
 		config->cqe_comp_fmt = tmp;
-	} else if (strcmp(MLX5_RXQ_PKT_PAD_EN, key) == 0) {
+	} else if (strcmp(MLX5_RXQ_CQE_PAD_EN, key) == 0) {
+		config->cqe_pad = !!tmp;
+ 	} else if (strcmp(MLX5_RXQ_PKT_PAD_EN, key) == 0) {
 		config->hw_padding = !!tmp;
 	} else if (strcmp(MLX5_RX_MPRQ_EN, key) == 0) {
 		config->mprq.enabled = !!tmp;
@@ -2352,6 +2357,12 @@ mlx5_port_args_config(struct mlx5_priv *priv, struct mlx5_kvargs_ctrl *mkvlist,
 	}
 	DRV_LOG(DEBUG, "Rx CQE compression is %ssupported.",
 		config->cqe_comp ? "" : "not ");
+	if (config->cqe_pad && !dev_cap->cqe_pad) {
+		DRV_LOG(WARNING, "Rx CQE padding isn't supported.");
+		config->cqe_pad = 0;
+	} else if (config->cqe_pad) {
+		DRV_LOG(INFO, "Rx CQE padding is enabled.");
+	}
 	if ((config->std_delay_drop || config->hp_delay_drop) &&
 	    !dev_cap->rq_delay_drop_en) {
 		config->std_delay_drop = 0;
diff --git a/drivers/net/mlx5/mlx5.h b/drivers/net/mlx5/mlx5.h
index 23a28f6..fa41b44 100644
--- a/drivers/net/mlx5/mlx5.h
+++ b/drivers/net/mlx5/mlx5.h
@@ -140,6 +140,7 @@ struct mlx5_dev_cap {
 	uint32_t txpp_en:1; /* Tx packet pacing is supported. */
 	uint32_t mpls_en:1; /* MPLS over GRE/UDP is supported. */
 	uint32_t cqe_comp:1; /* CQE compression is supported. */
+	uint32_t cqe_pad:1; /* CQE padding is supported. */
 	uint32_t hw_csum:1; /* Checksum offload is supported. */
 	uint32_t hw_padding:1; /* End alignment padding is supported. */
 	uint32_t dest_tir:1; /* Whether advanced DR API is available. */
@@ -264,6 +265,7 @@ struct mlx5_port_config {
 	unsigned int hw_vlan_insert:1; /* VLAN insertion in WQE is supported. */
 	unsigned int hw_padding:1; /* End alignment padding is supported. */
 	unsigned int cqe_comp:1; /* CQE compression is enabled. */
+	unsigned int cqe_pad:1; /* CQE padding is enabled. */
 	unsigned int cqe_comp_fmt:3; /* CQE compression format. */
 	unsigned int rx_vec_en:1; /* Rx vector is enabled. */
 	unsigned int std_delay_drop:1; /* Enable standard Rxq delay drop. */
-- 
2.7.4