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rdma/mlx5_dv: force RoCE IPv4 TOS 96 on RTR regardless of SL #6

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Merged
jleeh merged 1 commit into from
Aug 28, 2026
Merged

rdma/mlx5_dv: force RoCE IPv4 TOS 96 on RTR regardless of SL #6

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32 changes: 19 additions & 13 deletions lib/rdma_provider/rdma_provider_mlx5_dv.c
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Original file line number Diff line number Diff line change
Expand Up @@ -26,28 +26,34 @@ struct spdk_rdma_mlx5_dv_qp {
/*
* rdma_set_option(RDMA_OPTION_ID_TOS) programs SL (SQ / tx_prio). mlx5_dv
* moves the QP itself via ibv_modify_qp, so ConnectX builds the RoCEv2
* IPv4 header from the RTR AV traffic_class — which rdma_init_qp_attr
* often leaves 0. Fill TOS = SL<<5 (CS DSCP) when the AV is present and
* traffic_class is unset.
* IPv4 header from the RTR AV traffic_class. Inferring TOS from ah_attr.sl
* is a no-op: the RTR AV often has sl=0 even when the SQ is prio 3.
*
* Force IEEE 802.1p class 3 → TOS 96 / DSCP 24 (CS3), matching Longhorn
* dataEngineRdmaPriorityClass v2=3. Do not add IBV_QP_AV if the kernel
* did not already supply a full AV.
*/
#define RDMA_MLX5_DV_ROCE_TOS 96
#define RDMA_MLX5_DV_ROCE_SL 3

static void
rdma_mlx5_dv_fill_roce_tos(struct ibv_qp_attr *qp_attr, int qp_attr_mask)
{
uint8_t sl;

if ((qp_attr_mask & IBV_QP_AV) == 0) {
return;
}
if (qp_attr->ah_attr.grh.traffic_class != 0) {
SPDK_NOTICELOG("RoCE RTR missing IBV_QP_AV, cannot set TOS (mask=0x%x)\n",
qp_attr_mask);
return;
}

sl = qp_attr->ah_attr.sl;
if (sl == 0) {
return;
}
qp_attr->ah_attr.sl = RDMA_MLX5_DV_ROCE_SL;
qp_attr->ah_attr.grh.traffic_class = RDMA_MLX5_DV_ROCE_TOS;

qp_attr->ah_attr.grh.traffic_class = sl << 5;
SPDK_NOTICELOG("RoCE RTR TOS %u sl %u tclass %u is_global %d mask=0x%x\n",
RDMA_MLX5_DV_ROCE_TOS,
qp_attr->ah_attr.sl,
qp_attr->ah_attr.grh.traffic_class,
qp_attr->ah_attr.is_global,
qp_attr_mask);
}

static int
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