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eal/linux: select IOVA as VA mode for default case

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When bus layer reports the preferred mode as RTE_IOVA_DC then
select the RTE_IOVA_VA mode:

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

- By default, a mempool asks for IOVA-contiguous memory using
RTE_MEMZONE_IOVA_CONTIG. This is slow in RTE_IOVA_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>
Signed-off-by: David Marchand <david.marchand@redhat.com>
This commit is contained in:
Jerin Jacob 2019-07-22 14:56:53 +02:00 committed by Thomas Monjalon
parent d622cad892
commit bbe29a9bd7
2 changed files with 22 additions and 6 deletions
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22
doc/guides/prog_guide/env_abstraction_layer.rst
View File

@ -445,11 +445,29 @@ kernels.
- if the preferred mode is RTE_IOVA_PA but there is no access to Physical
Addresses, then EAL init fails 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 EAL selects the RTE_IOVA_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::
The RTE_IOVA_VA mode is selected as the default for the following reasons:
- All drivers are expected to 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``. This is slow in RTE_IOVA_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.
It is expected that all PCI drivers work in both RTE_IOVA_PA and
RTE_IOVA_VA modes.
If a PCI driver does not support RTE_IOVA_PA mode, the
``RTE_PCI_DRV_NEED_IOVA_AS_VA`` flag is used to dictate that this PCI
driver can only work in RTE_IOVA_VA mode.
IOVA Mode Configuration
~~~~~~~~~~~~~~~~~~~~~~~

6
lib/librte_eal/linux/eal/eal.c
View File

@ -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 */