66 lines
3.0 KiB
Plaintext
66 lines
3.0 KiB
Plaintext
|
What: /sys/kernel/iommu_groups/
|
||
|
|
Date: May 2012
|
||
|
|
KernelVersion: v3.5
|
||
|
|
Contact: Alex Williamson <alex.williamson@redhat.com>
|
||
|
|
Description: /sys/kernel/iommu_groups/ contains a number of sub-
|
||
|
|
directories, each representing an IOMMU group. The
|
||
|
|
name of the sub-directory matches the iommu_group_id()
|
||
|
|
for the group, which is an integer value. Within each
|
||
|
|
subdirectory is another directory named "devices" with
|
||
|
|
links to the sysfs devices contained in this group.
|
||
|
|
The group directory also optionally contains a "name"
|
||
|
|
file if the IOMMU driver has chosen to register a more
|
||
|
|
common name for the group.
|
||
|
|
Users:
|
||
|
|
|
||
|
|
What: /sys/kernel/iommu_groups/reserved_regions
|
||
|
|
Date: January 2017
|
||
|
|
KernelVersion: v4.11
|
||
|
|
Contact: Eric Auger <eric.auger@redhat.com>
|
||
|
|
Description: /sys/kernel/iommu_groups/reserved_regions list IOVA
|
||
|
|
regions that are reserved. Not necessarily all
|
||
|
|
reserved regions are listed. This is typically used to
|
||
|
|
output direct-mapped, MSI, non mappable regions. Each
|
||
|
|
region is described on a single line: the 1st field is
|
||
|
|
the base IOVA, the second is the end IOVA and the third
|
||
|
|
field describes the type of the region.
|
||
|
|
|
||
|
|
Since kernel 5.3, in case an RMRR is used only by graphics or
|
||
|
|
USB devices it is now exposed as "direct-relaxable" instead
|
||
|
|
of "direct". In device assignment use case, for instance,
|
||
|
|
those RMRR are considered to be relaxable and safe.
|
||
|
|
|
||
|
|
What: /sys/kernel/iommu_groups/<grp_id>/type
|
||
|
|
Date: November 2020
|
||
|
|
KernelVersion: v5.11
|
||
|
|
Contact: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
|
||
|
|
Description: /sys/kernel/iommu_groups/<grp_id>/type shows the type of default
|
||
|
|
domain in use by iommu for this group. See include/linux/iommu.h
|
||
|
|
for possible read values. A privileged user could request kernel to
|
||
|
|
change the group type by writing to this file. Valid write values:
|
||
|
|
|
||
|
|
======== ======================================================
|
||
|
|
DMA All the DMA transactions from the device in this group
|
||
|
|
are translated by the iommu.
|
||
|
|
DMA-FQ As above, but using batched invalidation to lazily
|
||
|
|
remove translations after use. This may offer reduced
|
||
|
|
overhead at the cost of reduced memory protection.
|
||
|
|
identity All the DMA transactions from the device in this group
|
||
|
|
are not translated by the iommu. Maximum performance
|
||
|
|
but zero protection.
|
||
|
|
auto Change to the type the device was booted with.
|
||
|
|
======== ======================================================
|
||
|
|
|
||
|
|
The default domain type of a group may be modified only when
|
||
|
|
|
||
|
|
- The group has only one device.
|
||
|
|
- The device in the group is not bound to any device driver.
|
||
|
|
So, the users must unbind the appropriate driver before
|
||
|
|
changing the default domain type.
|
||
|
|
|
||
|
|
Unbinding a device driver will take away the driver's control
|
||
|
|
over the device and if done on devices that host root file
|
||
|
|
system could lead to catastrophic effects (the users might
|
||
|
|
need to reboot the machine to get it to normal state). So, it's
|
||
|
|
expected that the users understand what they're doing.
|