[v3,4/4] eal: select IOVA mode as VA for default case

Message ID 20190718064543.33383-5-jerinj@marvell.com
State Superseded, archived
Delegated to: Thomas Monjalon
Headers show
Series
  • Fixes on IOVA mode selection
Related show

Checks

Context Check Description
ci/Intel-compilation success Compilation OK
ci/checkpatch success coding style OK

Commit Message

Jerin Jacob Kollanukkaran July 18, 2019, 6:45 a.m.
From: Jerin Jacob <jerinj@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@marvell.com>
Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>
---
 .../prog_guide/env_abstraction_layer.rst       | 18 ++++++++++++++++--
 lib/librte_eal/linux/eal/eal.c                 |  6 ++----
 2 files changed, 18 insertions(+), 6 deletions(-)

Patch

diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst
index 77307e3a6..b17c9dad9 100644
--- a/doc/guides/prog_guide/env_abstraction_layer.rst
+++ b/doc/guides/prog_guide/env_abstraction_layer.rst
@@ -445,11 +445,25 @@  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.
+
+#. It is easy to enable large amount of IOVA-contiguous memory use-cases with IOVA in VA mode.
+
   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.
 
+.. note::
+
+    If the device driver needs IOVA as VA and it cannot work with IOVA as PA
+    then the driver must request the PCI bus layer using  ``RTE_PCI_DRV_NEED_IOVA_AS_VA``
+    requirement flag. Absence of this flag, dictates, the driver must support both IOVA as PA and VA modes.
+
 IOVA Mode Configuration
 ~~~~~~~~~~~~~~~~~~~~~~~
 
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 */