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| author | Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com> | 2020-11-24 21:06:04 +0800 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2020-11-25 12:14:33 +0000 |
| commit | 63a816749d8670e4a92da5aecfb91238821a3d97 (patch) | |
| tree | 250fd5a29166580e770ec8d93185f2ac576cbfd7 | |
| parent | 0b8a96a3120ffe4d3571d93902693c59f90c3d0c (diff) | |
| download | linux-63a816749d8670e4a92da5aecfb91238821a3d97.tar.bz2 | |
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 <sai.praneeth.prakhya@intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Sohil Mehta <sohil.mehta@intel.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Link: https://lore.kernel.org/r/20201124130604.2912899-5-baolu.lu@linux.intel.com
Signed-off-by: Will Deacon <will@kernel.org>
| -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 <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 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. |