diff options
| author | Sai Praneeth Prakhya <[email protected]> | 2020-11-24 21:06:04 +0800 |
|---|---|---|
| committer | Will Deacon <[email protected]> | 2020-11-25 12:14:33 +0000 |
| commit | 63a816749d8670e4a92da5aecfb91238821a3d97 (patch) | |
| tree | 250fd5a29166580e770ec8d93185f2ac576cbfd7 | |
| parent | 0b8a96a3120ffe4d3571d93902693c59f90c3d0c (diff) | |
iommu: Document usage of "/sys/kernel/iommu_groups/<grp_id>/type" file
The default domain type of an iommu group can be changed by writing to
"/sys/kernel/iommu_groups/<grp_id>/type" file. Hence, document it's usage
and more importantly spell out its limitations.
Signed-off-by: Sai Praneeth Prakhya <[email protected]>
Signed-off-by: Lu Baolu <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: Ashok Raj <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Sohil Mehta <[email protected]>
Cc: Robin Murphy <[email protected]>
Cc: Jacob Pan <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>
| -rw-r--r-- | Documentation/ABI/testing/sysfs-kernel-iommu_groups | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-kernel-iommu_groups b/Documentation/ABI/testing/sysfs-kernel-iommu_groups index 017f5bc3920c..407b1628d7fd 100644 --- a/Documentation/ABI/testing/sysfs-kernel-iommu_groups +++ b/Documentation/ABI/testing/sysfs-kernel-iommu_groups @@ -33,3 +33,32 @@ 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 <[email protected]> +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 values. A privileged user could request kernel to + change the group type by writing to this file. Presently, only + three types of request are supported: + 1. DMA: All the DMA transactions from the device in this group + are translated by the iommu. + 2. identity: All the DMA transactions from the device in this + group are *not* translated by the iommu. + 3. auto: Change to the type the device was booted with. + Note: + ----- + The default domain type of a group may be modified only when + 1. The group has *only* one device + 2. 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. + Caution: + -------- + 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. |