+ void *uar;
+ uint32_t retry, uar_mapping;
+ void *base_addr;
+
+ for (retry = 0; retry < MLX5_ALLOC_UAR_RETRY; ++retry) {
+#ifdef MLX5DV_UAR_ALLOC_TYPE_NC
+ /* Control the mapping type according to the settings. */
+ uar_mapping = (mapping < 0) ?
+ MLX5DV_UAR_ALLOC_TYPE_NC : mapping;
+#else
+ /*
+ * It seems we have no way to control the memory mapping type
+ * for the UAR, the default "Write-Combining" type is supposed.
+ */
+ uar_mapping = 0;
+ RTE_SET_USED(mapping);
+#endif
+ uar = mlx5_glue->devx_alloc_uar(ctx, uar_mapping);
+#ifdef MLX5DV_UAR_ALLOC_TYPE_NC
+ if (!uar &&
+ mapping < 0 &&
+ uar_mapping == MLX5DV_UAR_ALLOC_TYPE_BF) {
+ /*
+ * In some environments like virtual machine the
+ * Write Combining mapped might be not supported and
+ * UAR allocation fails. We tried "Non-Cached" mapping
+ * for the case.
+ */
+ DRV_LOG(WARNING, "Failed to allocate DevX UAR (BF)");
+ uar_mapping = MLX5DV_UAR_ALLOC_TYPE_NC;
+ uar = mlx5_glue->devx_alloc_uar(ctx, uar_mapping);
+ } else if (!uar &&
+ mapping < 0 &&
+ uar_mapping == MLX5DV_UAR_ALLOC_TYPE_NC) {
+ /*
+ * If Verbs/kernel does not support "Non-Cached"
+ * try the "Write-Combining".
+ */
+ DRV_LOG(WARNING, "Failed to allocate DevX UAR (NC)");
+ uar_mapping = MLX5DV_UAR_ALLOC_TYPE_BF;
+ uar = mlx5_glue->devx_alloc_uar(ctx, uar_mapping);
+ }
+#endif
+ if (!uar) {
+ DRV_LOG(ERR, "Failed to allocate DevX UAR (BF/NC)");
+ rte_errno = ENOMEM;
+ goto exit;
+ }
+ base_addr = mlx5_os_get_devx_uar_base_addr(uar);
+ if (base_addr)