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![Mika Westerberg](/assets/img/avatar_default.png)
Recent systems with Thunderbolt ports may support IOMMU natively. In practice this means that Thunderbolt connected devices are placed behind an IOMMU during the whole time it is connected (including during boot) making Thunderbolt security levels redundant. This is called Kernel DMA protection [1] by Microsoft. Some of these systems still have Thunderbolt security level set to "user" in order to support OS downgrade (the older version of the OS might not support IOMMU based DMA protection so connecting a device still relies on user approval). Export this information to userspace by introducing a new sysfs attribute (iommu_dma_protection). Based on it userspace tools can make more accurate decision whether or not authorize the connected device. In addition update Thunderbolt documentation regarding IOMMU based DMA protection. [1] https://docs.microsoft.com/en-us/windows/security/information-protection/kernel-dma-protection-for-thunderbolt Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com> Reviewed-by: Yehezkel Bernat <YehezkelShB@gmail.com>
202 lines
7.5 KiB
Text
202 lines
7.5 KiB
Text
What: /sys/bus/thunderbolt/devices/.../domainX/boot_acl
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Date: Jun 2018
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KernelVersion: 4.17
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Contact: thunderbolt-software@lists.01.org
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Description: Holds a comma separated list of device unique_ids that
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are allowed to be connected automatically during system
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startup (e.g boot devices). The list always contains
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maximum supported number of unique_ids where unused
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entries are empty. This allows the userspace software
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to determine how many entries the controller supports.
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If there are multiple controllers, each controller has
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its own ACL list and size may be different between the
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controllers.
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System BIOS may have an option "Preboot ACL" or similar
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that needs to be selected before this list is taken into
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consideration.
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Software always updates a full list in each write.
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If a device is authorized automatically during boot its
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boot attribute is set to 1.
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What: /sys/bus/thunderbolt/devices/.../domainX/iommu_dma_protection
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Date: Mar 2019
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KernelVersion: 4.21
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Contact: thunderbolt-software@lists.01.org
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Description: This attribute tells whether the system uses IOMMU
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for DMA protection. Value of 1 means IOMMU is used 0 means
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it is not (DMA protection is solely based on Thunderbolt
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security levels).
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What: /sys/bus/thunderbolt/devices/.../domainX/security
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Date: Sep 2017
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KernelVersion: 4.13
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Contact: thunderbolt-software@lists.01.org
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Description: This attribute holds current Thunderbolt security level
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set by the system BIOS. Possible values are:
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none: All devices are automatically authorized
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user: Devices are only authorized based on writing
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appropriate value to the authorized attribute
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secure: Require devices that support secure connect at
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minimum. User needs to authorize each device.
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dponly: Automatically tunnel Display port (and USB). No
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PCIe tunnels are created.
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usbonly: Automatically tunnel USB controller of the
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connected Thunderbolt dock (and Display Port). All
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PCIe links downstream of the dock are removed.
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What: /sys/bus/thunderbolt/devices/.../authorized
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Date: Sep 2017
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KernelVersion: 4.13
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Contact: thunderbolt-software@lists.01.org
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Description: This attribute is used to authorize Thunderbolt devices
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after they have been connected. If the device is not
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authorized, no devices such as PCIe and Display port are
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available to the system.
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Contents of this attribute will be 0 when the device is not
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yet authorized.
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Possible values are supported:
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1: The device will be authorized and connected
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When key attribute contains 32 byte hex string the possible
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values are:
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1: The 32 byte hex string is added to the device NVM and
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the device is authorized.
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2: Send a challenge based on the 32 byte hex string. If the
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challenge response from device is valid, the device is
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authorized. In case of failure errno will be ENOKEY if
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the device did not contain a key at all, and
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EKEYREJECTED if the challenge response did not match.
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What: /sys/bus/thunderbolt/devices/.../boot
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Date: Jun 2018
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KernelVersion: 4.17
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Contact: thunderbolt-software@lists.01.org
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Description: This attribute contains 1 if Thunderbolt device was already
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authorized on boot and 0 otherwise.
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What: /sys/bus/thunderbolt/devices/.../key
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Date: Sep 2017
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KernelVersion: 4.13
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Contact: thunderbolt-software@lists.01.org
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Description: When a devices supports Thunderbolt secure connect it will
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have this attribute. Writing 32 byte hex string changes
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authorization to use the secure connection method instead.
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Writing an empty string clears the key and regular connection
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method can be used again.
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What: /sys/bus/thunderbolt/devices/.../device
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Date: Sep 2017
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KernelVersion: 4.13
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Contact: thunderbolt-software@lists.01.org
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Description: This attribute contains id of this device extracted from
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the device DROM.
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What: /sys/bus/thunderbolt/devices/.../device_name
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Date: Sep 2017
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KernelVersion: 4.13
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Contact: thunderbolt-software@lists.01.org
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Description: This attribute contains name of this device extracted from
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the device DROM.
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What: /sys/bus/thunderbolt/devices/.../vendor
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Date: Sep 2017
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KernelVersion: 4.13
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Contact: thunderbolt-software@lists.01.org
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Description: This attribute contains vendor id of this device extracted
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from the device DROM.
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What: /sys/bus/thunderbolt/devices/.../vendor_name
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Date: Sep 2017
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KernelVersion: 4.13
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Contact: thunderbolt-software@lists.01.org
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Description: This attribute contains vendor name of this device extracted
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from the device DROM.
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What: /sys/bus/thunderbolt/devices/.../unique_id
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Date: Sep 2017
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KernelVersion: 4.13
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Contact: thunderbolt-software@lists.01.org
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Description: This attribute contains unique_id string of this device.
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This is either read from hardware registers (UUID on
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newer hardware) or based on UID from the device DROM.
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Can be used to uniquely identify particular device.
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What: /sys/bus/thunderbolt/devices/.../nvm_version
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Date: Sep 2017
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KernelVersion: 4.13
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Contact: thunderbolt-software@lists.01.org
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Description: If the device has upgradeable firmware the version
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number is available here. Format: %x.%x, major.minor.
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If the device is in safe mode reading the file returns
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-ENODATA instead as the NVM version is not available.
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What: /sys/bus/thunderbolt/devices/.../nvm_authenticate
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Date: Sep 2017
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KernelVersion: 4.13
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Contact: thunderbolt-software@lists.01.org
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Description: When new NVM image is written to the non-active NVM
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area (through non_activeX NVMem device), the
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authentication procedure is started by writing 1 to
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this file. If everything goes well, the device is
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restarted with the new NVM firmware. If the image
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verification fails an error code is returned instead.
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When read holds status of the last authentication
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operation if an error occurred during the process. This
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is directly the status value from the DMA configuration
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based mailbox before the device is power cycled. Writing
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0 here clears the status.
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What: /sys/bus/thunderbolt/devices/<xdomain>.<service>/key
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Date: Jan 2018
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KernelVersion: 4.15
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Contact: thunderbolt-software@lists.01.org
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Description: This contains name of the property directory the XDomain
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service exposes. This entry describes the protocol in
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question. Following directories are already reserved by
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the Apple XDomain specification:
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network: IP/ethernet over Thunderbolt
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targetdm: Target disk mode protocol over Thunderbolt
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extdisp: External display mode protocol over Thunderbolt
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What: /sys/bus/thunderbolt/devices/<xdomain>.<service>/modalias
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Date: Jan 2018
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KernelVersion: 4.15
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Contact: thunderbolt-software@lists.01.org
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Description: Stores the same MODALIAS value emitted by uevent for
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the XDomain service. Format: tbtsvc:kSpNvNrN
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What: /sys/bus/thunderbolt/devices/<xdomain>.<service>/prtcid
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Date: Jan 2018
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KernelVersion: 4.15
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Contact: thunderbolt-software@lists.01.org
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Description: This contains XDomain protocol identifier the XDomain
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service supports.
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What: /sys/bus/thunderbolt/devices/<xdomain>.<service>/prtcvers
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Date: Jan 2018
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KernelVersion: 4.15
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Contact: thunderbolt-software@lists.01.org
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Description: This contains XDomain protocol version the XDomain
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service supports.
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What: /sys/bus/thunderbolt/devices/<xdomain>.<service>/prtcrevs
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Date: Jan 2018
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KernelVersion: 4.15
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Contact: thunderbolt-software@lists.01.org
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Description: This contains XDomain software version the XDomain
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service supports.
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What: /sys/bus/thunderbolt/devices/<xdomain>.<service>/prtcstns
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Date: Jan 2018
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KernelVersion: 4.15
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Contact: thunderbolt-software@lists.01.org
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Description: This contains XDomain service specific settings as
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bitmask. Format: %x
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