Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

[linux-2.6-microblaze.git] / Documentation / ABI / testing / sysfs-kernel-iommu_groups

diff --git a/Documentation/ABI/testing/sysfs-kernel-iommu_groups b/Documentation/ABI/testing/sysfs-kernel-iommu_groups
index 017f5bc..0fedbb0 100644 (file)
--- a/Documentation/ABI/testing/sysfs-kernel-iommu_groups
+++ b/Documentation/ABI/testing/sysfs-kernel-iommu_groups
@@ -33,3 +33,33 @@ Description:    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.
+               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.