issue: 4213201 Remove memset for the next hot WQE

XLIO does a prefetch with zeroing the next WQEBB after a doorbell. It
also presets inline_hdr_sz as a legacy behavior.

However, in a corner case when the producer fills the tail WQE and the
consumer is still processing the head WQE, the prefetch code corrupts
the head WQE.

Remove the prefetch to avoid the SQ corruption. Clear each WQE before
filling it.

Signed-off-by: Dmytro Podgornyi <[email protected]>

Author: pasis

src/core/dev/hw_queue_tx.cpp

@@ -488,13 +488,6 @@ void hw_queue_tx::init_queue()
     hwqtx_logfunc("m_tx_num_wr=%d max_inline_data: %d m_sq_wqe_idx_to_prop=%p", m_tx_num_wr,
                   get_max_inline_data(), m_sq_wqe_idx_to_prop);
 
-    memset((void *)(uintptr_t)m_sq_wqe_hot, 0, sizeof(struct mlx5_eth_wqe));
-    m_sq_wqe_hot->ctrl.data[0] = htonl(MLX5_OPCODE_SEND);
-    m_sq_wqe_hot->ctrl.data[1] = htonl((m_mlx5_qp.qpn << 8) | 4);
-    m_sq_wqe_hot->ctrl.data[2] = 0;
-    m_sq_wqe_hot->eseg.inline_hdr_sz = htons(MLX5_ETH_INLINE_HEADER_SIZE);
-    m_sq_wqe_hot->eseg.cs_flags = XLIO_TX_PACKET_L3_CSUM | XLIO_TX_PACKET_L4_CSUM;
-
     hwqtx_logfunc("%p allocated for %d QPs sq_wqes:%p sq_wqes_end: %p and configured %d WRs "
                   "BlueFlame: %p",
                   m_mlx5_qp.qp, m_mlx5_qp.qpn, m_sq_wqes, m_sq_wqes_end, m_tx_num_wr,
@@ -515,15 +508,9 @@ void hw_queue_tx::init_device_memory()
 
 void hw_queue_tx::update_next_wqe_hot()
 {
-    // Preparing next WQE as Ethernet send WQE and index:
+    // Preparing pointer to the next WQE after a doorbell
     m_sq_wqe_hot = &(*m_sq_wqes)[m_sq_wqe_counter & (m_tx_num_wr - 1)];
     m_sq_wqe_hot_index = m_sq_wqe_counter & (m_tx_num_wr - 1);
-    memset(m_sq_wqe_hot, 0, sizeof(mlx5_eth_wqe));
-
-    // Fill Ethernet segment with header inline:
-    struct mlx5_wqe_eth_seg *eth_seg =
-        (struct mlx5_wqe_eth_seg *)((uint8_t *)m_sq_wqe_hot + sizeof(struct mlx5_wqe_ctrl_seg));
-    eth_seg->inline_hdr_sz = htons(MLX5_ETH_INLINE_HEADER_SIZE);
 }
 
 cq_mgr_tx *hw_queue_tx::init_tx_cq_mgr()
@@ -610,6 +597,10 @@ inline int hw_queue_tx::fill_wqe(xlio_ibv_send_wr *pswr)
             "wqe_hot:%p num_sge: %d data_addr: %p data_len: %d max_inline_len: %d inline_len: %d",
             m_sq_wqe_hot, pswr->num_sge, data_addr, data_len, max_inline_len, inline_len);
 
+        struct mlx5_wqe_eth_seg *eth_seg =
+            (struct mlx5_wqe_eth_seg *)((uint8_t *)m_sq_wqe_hot + sizeof(struct mlx5_wqe_ctrl_seg));
+        eth_seg->inline_hdr_sz = htons(MLX5_ETH_INLINE_HEADER_SIZE);
+
         // Fill Ethernet segment with header inline, static data
         // were populated in preset after previous packet send
         memcpy(cur_seg + offsetof(struct mlx5_wqe_eth_seg, inline_hdr_start), data_addr,
@@ -851,6 +842,8 @@ void hw_queue_tx::send_to_wire(xlio_ibv_send_wr *p_send_wqe, xlio_wr_tx_packet_a
     ctrl = (struct xlio_mlx5_wqe_ctrl_seg *)m_sq_wqe_hot;
     eseg = (struct mlx5_wqe_eth_seg *)((uint8_t *)m_sq_wqe_hot + sizeof(*ctrl));
 
+    memset(m_sq_wqe_hot, 0, sizeof(mlx5_eth_wqe));
+
     /* Configure ctrl segment
      * qpn_ds or ctrl.data[1] is set inside fill_wqe()
      */
@@ -1261,7 +1254,6 @@ inline void hw_queue_tx::tls_post_static_params_wqe(xlio_ti *ti, const struct xl
      * one WQEBB and will be posted before m_sq_wqes_end.
      */
 
-    // XXX: We set inline_hdr_sz for every new hot wqe. This corrupts UMR WQE without memset().
     memset(m_sq_wqe_hot, 0, sizeof(*m_sq_wqe_hot));
     cseg->opmod_idx_opcode =
         htobe32(((m_sq_wqe_counter & 0xffff) << 8) | MLX5_OPCODE_UMR | (opmod << 24));