net/mlx5: fix Rx packet padding

Rx packet padding is supposed to be set by an environment variable -
MLX5_PMD_ENABLE_PADDING, but it has been missing for some time by mistake.
Rather than using such a variable, a PMD parameter (rxq_pkt_pad_en) is
added instead.

Fixes: a1366b1a2be3 ("net/mlx5: add reference counter on DPDK Rx queues")
Cc: stable@dpdk.org
Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
Reviewed-by: Erez Ferber <erezf@mellanox.com>
Acked-by: Shahaf Shuler <shahafs@mellanox.com>

diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst
index 5ddca44..3f168b1 100644 (file)
--- a/doc/guides/nics/mlx5.rst
+++ b/doc/guides/nics/mlx5.rst
@@ -233,20 +233,6 @@ Environment variables
   enabled and most useful when ``CONFIG_RTE_EAL_PMD_PATH`` is also set,
   since ``LD_LIBRARY_PATH`` has no effect in this case.
 
-- ``MLX5_PMD_ENABLE_PADDING``
-
-  Enables HW packet padding in PCI bus transactions.
-
-  When packet size is cache aligned and CRC stripping is enabled, 4 fewer
-  bytes are written to the PCI bus. Enabling padding makes such packets
-  aligned again.
-
-  In cases where PCI bandwidth is the bottleneck, padding can improve
-  performance by 10%.
-
-  This is disabled by default since this can also decrease performance for
-  unaligned packet sizes.
-
 - ``MLX5_SHUT_UP_BF``
 
   Configures HW Tx doorbell register as IO-mapped.
@@ -301,6 +287,19 @@ Run-time configuration
 
   - 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
+  transaction. This feature would waste PCI bandwidth but could improve
+  performance by avoiding partial cacheline write which may cause costly
+  read-modify-copy in memory transaction on some architectures. Disabled by
+  default.
+
+  Supported on:
+
+  - x86_64 with ConnectX-4, ConnectX-4 LX, ConnectX-5, ConnectX-6 and Bluefield.
+  - POWER8 and ARMv8 with ConnectX-4 LX, ConnectX-5, ConnectX-6 and Bluefield.
+
 - ``mprq_en`` parameter [int]
 
   A nonzero value enables configuring Multi-Packet Rx queues. Rx queue is

diff --git a/drivers/net/mlx5/mlx5.c b/drivers/net/mlx5/mlx5.c
index a84e1af..741bc7f 100644 (file)
--- a/drivers/net/mlx5/mlx5.c
+++ b/drivers/net/mlx5/mlx5.c
@@ -54,6 +54,9 @@
 /* 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"
+
 /* Device parameter to enable Multi-Packet Rx queue. */
 #define MLX5_RX_MPRQ_EN "mprq_en"
 
@@ -486,6 +489,8 @@ mlx5_args_check(const char *key, const char *val, void *opaque)
                config->cqe_comp = !!tmp;
        } 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;
        } else if (strcmp(MLX5_RX_MPRQ_LOG_STRIDE_NUM, key) == 0) {
@@ -541,6 +546,7 @@ mlx5_args(struct mlx5_dev_config *config, struct rte_devargs *devargs)
        const char **params = (const char *[]){
                MLX5_RXQ_CQE_COMP_EN,
                MLX5_RXQ_CQE_PAD_EN,
+               MLX5_RXQ_PKT_PAD_EN,
                MLX5_RX_MPRQ_EN,
                MLX5_RX_MPRQ_LOG_STRIDE_NUM,
                MLX5_RX_MPRQ_MAX_MEMCPY_LEN,
@@ -735,6 +741,7 @@ mlx5_dev_spawn(struct rte_device *dpdk_dev,
        struct rte_eth_dev *eth_dev = NULL;
        struct priv *priv = NULL;
        int err = 0;
+       unsigned int hw_padding = 0;
        unsigned int mps;
        unsigned int cqe_comp;
        unsigned int cqe_pad = 0;
@@ -1060,10 +1067,14 @@ mlx5_dev_spawn(struct rte_device *dpdk_dev,
        DRV_LOG(DEBUG, "FCS stripping configuration is %ssupported",
                (config.hw_fcs_strip ? "" : "not "));
 #ifdef HAVE_IBV_WQ_FLAG_RX_END_PADDING
-       config.hw_padding = !!attr.rx_pad_end_addr_align;
+       hw_padding = !!attr.rx_pad_end_addr_align;
 #endif
-       DRV_LOG(DEBUG, "hardware Rx end alignment padding is %ssupported",
-               (config.hw_padding ? "" : "not "));
+       if (config.hw_padding && !hw_padding) {
+               DRV_LOG(DEBUG, "Rx end alignment padding isn't supported");
+               config.hw_padding = 0;
+       } else if (config.hw_padding) {
+               DRV_LOG(DEBUG, "Rx end alignment padding is enabled");
+       }
        config.tso = (attr.tso_caps.max_tso > 0 &&
                      (attr.tso_caps.supported_qpts &
                       (1 << IBV_QPT_RAW_PACKET)));
@@ -1440,6 +1451,7 @@ mlx5_pci_probe(struct rte_pci_driver *pci_drv __rte_unused,
                qsort(list, n, sizeof(*list), mlx5_dev_spawn_data_cmp);
        /* Default configuration. */
        dev_config = (struct mlx5_dev_config){
+               .hw_padding = 0,
                .mps = MLX5_ARG_UNSET,
                .tx_vec_en = 1,
                .rx_vec_en = 1,