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Diffstat (limited to '')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-kernel-iommu_groups | 46 |
1 files changed, 38 insertions, 8 deletions
diff --git a/Documentation/ABI/testing/sysfs-kernel-iommu_groups b/Documentation/ABI/testing/sysfs-kernel-iommu_groups index 017f5bc3920c..b15af6a5bc08 100644 --- a/Documentation/ABI/testing/sysfs-kernel-iommu_groups +++ b/Documentation/ABI/testing/sysfs-kernel-iommu_groups @@ -25,11 +25,41 @@ Description: /sys/kernel/iommu_groups/reserved_regions list IOVA the base IOVA, the second is the end IOVA and the third field describes the type of the region. -What: /sys/kernel/iommu_groups/reserved_regions -Date: June 2019 -KernelVersion: v5.3 -Contact: Eric Auger <eric.auger@redhat.com> -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. + 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. |