VFIO kernel is usually present by default in all distributions,
however please consult your distributions documentation to make sure that is the case.
+For DMA mapping of either external memory or hugepages, VFIO interface is used.
+VFIO does not support partial unmap of once mapped memory. Hence DPDK's memory is
+mapped in hugepage granularity or system page granularity. Number of DMA
+mappings is limited by kernel with user locked memory limit of a process (rlimit)
+for system/hugepage memory. Another per-container overall limit applicable both
+for external memory and system memory was added in kernel 5.1 defined by
+VFIO module parameter ``dma_entry_limit`` with a default value of 64K.
+When application is out of DMA entries, these limits need to be adjusted to
+increase the allowed limit.
+
Since Linux version 5.7,
the ``vfio-pci`` module supports the creation of virtual functions.
After the PF is bound to ``vfio-pci`` module,
For proper operation of VFIO when running DPDK applications as a non-privileged user, correct permissions should also be set up.
For more information, please refer to :ref:`Running_Without_Root_Privileges`.
+VFIO no-IOMMU mode
+------------------
+
+If there is no IOMMU available on the system, VFIO can still be used,
+but it has to be loaded with an additional module parameter:
+
+.. code-block:: console
+
+ modprobe vfio enable_unsafe_noiommu_mode=1
+
+Alternatively, one can also enable this option in an already loaded kernel module:
+
+.. code-block:: console
+
+ echo 1 > /sys/module/vfio/parameters/enable_unsafe_noiommu_mode
+
+After that, VFIO can be used with hardware devices as usual.
+
.. note::
- VFIO can be used without IOMMU.
- While this is unsafe, it does make it possible for the user
+ It may be required to unload all VFIO related-modules before probing
+ the module again with ``enable_unsafe_noiommu_mode=1`` parameter.
+
+.. warning::
+
+ Since no-IOMMU mode forgoes IOMMU protection, it is inherently unsafe.
+ That said, it does make it possible for the user
to keep the degree of device access and programming that VFIO has,
in situations where IOMMU is not available.
.. code-block:: console
./usertools/dpdk-devbind.py --bind=ixgbe 82:00.0
+
+Troubleshooting VFIO
+--------------------
+
+In certain situations, using ``dpdk-devbind.py`` script
+to bind a device to VFIO driver may fail.
+The first place to check is the kernel messages:
+
+.. code-block:: console
+
+ dmesg | tail
+ ...
+ [ 1297.875090] vfio-pci: probe of 0000:31:00.0 failed with error -22
+ ...
+
+In most cases, the ``error -22`` indicates that the VFIO subsystem
+could not be enabled because there is no IOMMU support.
+
+To check whether the kernel has been booted with correct parameters,
+one can check the kernel command-line:
+
+.. code-block:: console
+
+ cat /proc/cmdline
+
+Please refer to earlier sections on how to configure kernel parameters
+correctly for your system.
+
+If the kernel is configured correctly, one also has to make sure that
+the BIOS configuration has virtualization features (such as Intel® VT-d).
+There is no standard way to check if the platform is configured correctly,
+so please check with your platform documentation to see if it has such features,
+and how to enable them.
+
+In certain distributions, default kernel configuration is such that
+the no-IOMMU mode is disabled altogether at compile time.
+This can be checked in the boot configuration of your system:
+
+.. code-block:: console
+
+ cat /boot/config-$(uname -r) | grep NOIOMMU
+ # CONFIG_VFIO_NOIOMMU is not set
+
+If ``CONFIG_VFIO_NOIOMMU`` is not enabled in the kernel configuration,
+VFIO driver will not support the no-IOMMU mode,
+and other alternatives (such as UIO drivers) will have to be used.
git.droids-corp.org / dpdk.git / blobdiff