verbs: Allow query only device support for QP data in order

Add a flag to query directly the device support for QP data-in-order
semantics without enforcing host CPU architecture restrictions. It is
particularly useful in scenarios where the GPU performs data polling
directly.

Reviewed-by: Michael Margolin <[email protected]>
Reviewed-by: Yonatan Nachum <[email protected]>
Signed-off-by: Daniel Kranzdorf <[email protected]>

Author: dkkranz

libibverbs/man/ibv_query_qp_data_in_order.3.md

@@ -45,6 +45,9 @@ This function describes ordering at the receiving side of the QP, not the sendin
 
 IBV_QUERY_QP_DATA_IN_ORDER_RETURN_CAPS - Query for supported capabilities and return a capabilities vector.
 
+IBV_QUERY_QP_DATA_IN_ORDER_DEVICE_ONLY - Allows querying device support for data-in-order semantics
+    without enforcing host CPU architecture restrictions.
+
 Passing 0 is equivalent to using IBV_QUERY_QP_DATA_IN_ORDER_RETURN_CAPS and checking for IBV_QUERY_QP_DATA_IN_ORDER_WHOLE_MSG support.
 
 # RETURN VALUE

libibverbs/verbs.c

@@ -695,23 +695,26 @@ LATEST_SYMVER_FUNC(ibv_query_qp, 1_1, "IBVERBS_1.1",
 int ibv_query_qp_data_in_order(struct ibv_qp *qp, enum ibv_wr_opcode op,
 			       uint32_t flags)
 {
+	int result;
+
+	if (!check_comp_mask(flags, IBV_QUERY_QP_DATA_IN_ORDER_RETURN_CAPS))
+		return 0;
+
 #if !defined(__i386__) && !defined(__x86_64__)
 	/* Currently this API is only supported for x86 architectures since most
 	 * non-x86 platforms are known to be OOO and need to do a per-platform study.
+	 * However, it is possible to override this restriction to allow querying
+	 * the device capability directly, regardless of the host CPU architecture.
 	 */
-	return 0;
-#else
-	int result;
-
-	if (!check_comp_mask(flags, IBV_QUERY_QP_DATA_IN_ORDER_RETURN_CAPS))
+	if (!(flags & IBV_QUERY_QP_DATA_IN_ORDER_DEVICE_ONLY))
 		return 0;
+#endif
 
 	result = get_ops(qp->context)->query_qp_data_in_order(qp, op, flags);
 	if (result & IBV_QUERY_QP_DATA_IN_ORDER_WHOLE_MSG)
 		result |= IBV_QUERY_QP_DATA_IN_ORDER_ALIGNED_128_BYTES;
 
 	return flags ? result : !!(result & IBV_QUERY_QP_DATA_IN_ORDER_WHOLE_MSG);
-#endif
 }
 
 LATEST_SYMVER_FUNC(ibv_modify_qp, 1_1, "IBVERBS_1.1",

libibverbs/verbs.h

@@ -1042,6 +1042,7 @@ enum ibv_qp_attr_mask {
 
 enum ibv_query_qp_data_in_order_flags {
 	IBV_QUERY_QP_DATA_IN_ORDER_RETURN_CAPS = 1 << 0,
+	IBV_QUERY_QP_DATA_IN_ORDER_DEVICE_ONLY = 1 << 1,
 };
 
 enum ibv_query_qp_data_in_order_caps {