On 19/11/2020 11:32, Anatoly Burakov wrote: > There are common problems with VFIO that get asked over and over on the > mailing list. Document common problems with VFIO and how to fix them or > at least figure out what went wrong. > > Signed-off-by: Anatoly Burakov <anatoly.bura...@intel.com> > --- > doc/guides/linux_gsg/linux_drivers.rst | 43 ++++++++++++++++++++++++++ > 1 file changed, 43 insertions(+) > > diff --git a/doc/guides/linux_gsg/linux_drivers.rst > b/doc/guides/linux_gsg/linux_drivers.rst > index 9c61850dbb..f3c06c68d1 100644 > --- a/doc/guides/linux_gsg/linux_drivers.rst > +++ b/doc/guides/linux_gsg/linux_drivers.rst > @@ -276,3 +276,46 @@ To restore device ``82:00.0`` to its original kernel > binding: > .. code-block:: console > > ./usertools/dpdk-devbind.py --bind=ixgbe 82:00.0 > + > +Troubleshooting VFIO > +-------------------- > + > +In certain situations, using ``dpdk-devbind.py`` script to bing 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 couldn't > 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. >
Good to have some debug hints and it avoids a backport ;-) With Bruce's s/bing/bind/ Acked-by: Kevin Traynor <ktray...@redhat.com>
