From 63a816749d8670e4a92da5aecfb91238821a3d97 Mon Sep 17 00:00:00 2001 From: Sai Praneeth Prakhya Date: Tue, 24 Nov 2020 21:06:04 +0800 Subject: iommu: Document usage of "/sys/kernel/iommu_groups//type" file The default domain type of an iommu group can be changed by writing to "/sys/kernel/iommu_groups//type" file. Hence, document it's usage and more importantly spell out its limitations. Signed-off-by: Sai Praneeth Prakhya Signed-off-by: Lu Baolu Cc: Christoph Hellwig Cc: Joerg Roedel Cc: Ashok Raj Cc: Will Deacon Cc: Sohil Mehta Cc: Robin Murphy Cc: Jacob Pan Link: https://lore.kernel.org/r/20201124130604.2912899-5-baolu.lu@linux.intel.com Signed-off-by: Will Deacon --- .../ABI/testing/sysfs-kernel-iommu_groups | 29 ++++++++++++++++++++++ 1 file changed, 29 insertions(+) (limited to 'Documentation/ABI/testing') 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//type +Date: November 2020 +KernelVersion: v5.11 +Contact: Sai Praneeth Prakhya +Description: /sys/kernel/iommu_groups//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. -- cgit v1.2.3 From 62c9917d9c1041ba175ccf1bc4c010efc0188a2e Mon Sep 17 00:00:00 2001 From: Lu Baolu Date: Thu, 26 Nov 2020 17:06:03 +0800 Subject: iommu: Fix htmldocs warnings in sysfs-kernel-iommu_groups Below warnings are fixed: Documentation/ABI/testing/sysfs-kernel-iommu_groups:38: WARNING: Unexpected indentation. Documentation/ABI/testing/sysfs-kernel-iommu_groups:38: WARNING: Block quote ends without a blank line; unexpected unindent. Documentation/ABI/testing/sysfs-kernel-iommu_groups:38: WARNING: Enumerated list ends without a blank line; unexpected unindent. Documentation/ABI/testing/sysfs-kernel-iommu_groups:38: WARNING: Unexpected indentation. Documentation/ABI/testing/sysfs-kernel-iommu_groups:38: WARNING: Block quote ends without a blank line; unexpected unindent. Fixes: 63a816749d86 ("iommu: Document usage of "/sys/kernel/iommu_groups//type" file") Reported-by: Stephen Rothwell Link: https://lore.kernel.org/linux-next/20201126174851.200e0e58@canb.auug.org.au/ Signed-off-by: Lu Baolu Link: https://lore.kernel.org/r/20201126090603.1511589-1-baolu.lu@linux.intel.com Signed-off-by: Will Deacon --- .../ABI/testing/sysfs-kernel-iommu_groups | 33 +++++++++++----------- 1 file changed, 17 insertions(+), 16 deletions(-) (limited to 'Documentation/ABI/testing') diff --git a/Documentation/ABI/testing/sysfs-kernel-iommu_groups b/Documentation/ABI/testing/sysfs-kernel-iommu_groups index 407b1628d7fd..0fedbb0f94e4 100644 --- a/Documentation/ABI/testing/sysfs-kernel-iommu_groups +++ b/Documentation/ABI/testing/sysfs-kernel-iommu_groups @@ -40,23 +40,24 @@ KernelVersion: v5.11 Contact: Sai Praneeth Prakhya Description: /sys/kernel/iommu_groups//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: - ----- + 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 - 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: - -------- + + - 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 -- cgit v1.2.3