[dpdk-dev] [PATCH v2 4/4] eal: select IOVA mode as VA for default case

[jerinj at marvell.com]

From: Jerin Jacob <jerinj at marvell.com>

When bus layer selected the preferred mode as RTE_IOVA_DC then
select the IOVA mode as RTE_IOVA_VA.

The RTE_IOVA_VA selected as the default because,

1) All drivers work in RTE_IOVA_VA mode, irrespective of physical
address availability.

2) By default, the mempool, first asks for IOVA-contiguous memory
using RTE_MEMZONE_IOVA_CONTIG and this is slow in IOVA as PA mode
and it may affect the application boot time.

Signed-off-by: Jerin Jacob <jerinj at marvell.com>
---
 doc/guides/prog_guide/env_abstraction_layer.rst | 10 ++++++++--
 lib/librte_eal/linux/eal/eal.c                  |  6 ++----
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst
index 77307e3a6..1b0343eee 100644
--- a/doc/guides/prog_guide/env_abstraction_layer.rst
+++ b/doc/guides/prog_guide/env_abstraction_layer.rst
@@ -445,8 +445,14 @@ kernels.
 - if the preferred mode is RTE_IOVA_PA but there is no access to Physical
   Addresses, then EAL init will fail early, since later probing of the devices
   would fail anyway,
-- if the preferred mode is RTE_IOVA_DC then based on the Physical Addresses
-  availability, the preferred mode is adjusted to RTE_IOVA_PA or RTE_IOVA_VA.
+- if the preferred mode is RTE_IOVA_DC then select the IOVA mode as RTE_IOVA_VA.
+  The RTE_IOVA_VA selected as the default because,
+
+#. All drivers work in RTE_IOVA_VA mode, irrespective of physical address availability.
+
+#. By default, the mempool, first asks for IOVA-contiguous memory using ``RTE_MEMZONE_IOVA_CONTIG``,
+   and this is slow in IOVA as PA mode and it may affect the application boot time.
+
   In the case when the buses had disagreed on the IOVA Mode at the first step,
   part of the buses won't work because of this decision.
 
diff --git a/lib/librte_eal/linux/eal/eal.c b/lib/librte_eal/linux/eal/eal.c
index 2e5499f9b..34db78753 100644
--- a/lib/librte_eal/linux/eal/eal.c
+++ b/lib/librte_eal/linux/eal/eal.c
@@ -1061,10 +1061,8 @@ rte_eal_init(int argc, char **argv)
 		enum rte_iova_mode iova_mode = rte_bus_get_iommu_class();
 
 		if (iova_mode == RTE_IOVA_DC) {
-			iova_mode = phys_addrs ? RTE_IOVA_PA : RTE_IOVA_VA;
-			RTE_LOG(DEBUG, EAL,
-				"Buses did not request a specific IOVA mode, using '%s' based on physical addresses availability.\n",
-				phys_addrs ? "PA" : "VA");
+			iova_mode = RTE_IOVA_VA;
+			RTE_LOG(DEBUG, EAL, "Buses did not request a specific IOVA mode, select IOVA as VA mode.\n");
 		}
 #ifdef RTE_LIBRTE_KNI
 		/* Workaround for KNI which requires physical address to work */
-- 
2.22.0