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.
+ identity All the DMA transactions from the device in this group
+ are not translated by the iommu.
+ 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.