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| -rw-r--r-- | Documentation/ABI/testing/sysfs-kernel-iommu_groups | 65 |
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diff --git a/Documentation/ABI/testing/sysfs-kernel-iommu_groups b/Documentation/ABI/testing/sysfs-kernel-iommu_groups new file mode 100644 index 000000000..b15af6a5b --- /dev/null +++ b/Documentation/ABI/testing/sysfs-kernel-iommu_groups @@ -0,0 +1,65 @@ +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. |