239 lines
10 KiB
ReStructuredText
239 lines
10 KiB
ReStructuredText
=============
|
|
Thunderbolt
|
|
=============
|
|
The interface presented here is not meant for end users. Instead there
|
|
should be a userspace tool that handles all the low-level details, keeps
|
|
a database of the authorized devices and prompts users for new connections.
|
|
|
|
More details about the sysfs interface for Thunderbolt devices can be
|
|
found in ``Documentation/ABI/testing/sysfs-bus-thunderbolt``.
|
|
|
|
Those users who just want to connect any device without any sort of
|
|
manual work can add following line to
|
|
``/etc/udev/rules.d/99-local.rules``::
|
|
|
|
ACTION=="add", SUBSYSTEM=="thunderbolt", ATTR{authorized}=="0", ATTR{authorized}="1"
|
|
|
|
This will authorize all devices automatically when they appear. However,
|
|
keep in mind that this bypasses the security levels and makes the system
|
|
vulnerable to DMA attacks.
|
|
|
|
Security levels and how to use them
|
|
-----------------------------------
|
|
Starting with Intel Falcon Ridge Thunderbolt controller there are 4
|
|
security levels available. The reason for these is the fact that the
|
|
connected devices can be DMA masters and thus read contents of the host
|
|
memory without CPU and OS knowing about it. There are ways to prevent
|
|
this by setting up an IOMMU but it is not always available for various
|
|
reasons.
|
|
|
|
The security levels are as follows:
|
|
|
|
none
|
|
All devices are automatically connected by the firmware. No user
|
|
approval is needed. In BIOS settings this is typically called
|
|
*Legacy mode*.
|
|
|
|
user
|
|
User is asked whether the device is allowed to be connected.
|
|
Based on the device identification information available through
|
|
``/sys/bus/thunderbolt/devices``, the user then can make the decision.
|
|
In BIOS settings this is typically called *Unique ID*.
|
|
|
|
secure
|
|
User is asked whether the device is allowed to be connected. In
|
|
addition to UUID the device (if it supports secure connect) is sent
|
|
a challenge that should match the expected one based on a random key
|
|
written to the ``key`` sysfs attribute. In BIOS settings this is
|
|
typically called *One time saved key*.
|
|
|
|
dponly
|
|
The firmware automatically creates tunnels for Display Port and
|
|
USB. No PCIe tunneling is done. In BIOS settings this is
|
|
typically called *Display Port Only*.
|
|
|
|
The current security level can be read from
|
|
``/sys/bus/thunderbolt/devices/domainX/security`` where ``domainX`` is
|
|
the Thunderbolt domain the host controller manages. There is typically
|
|
one domain per Thunderbolt host controller.
|
|
|
|
If the security level reads as ``user`` or ``secure`` the connected
|
|
device must be authorized by the user before PCIe tunnels are created
|
|
(e.g the PCIe device appears).
|
|
|
|
Each Thunderbolt device plugged in will appear in sysfs under
|
|
``/sys/bus/thunderbolt/devices``. The device directory carries
|
|
information that can be used to identify the particular device,
|
|
including its name and UUID.
|
|
|
|
Authorizing devices when security level is ``user`` or ``secure``
|
|
-----------------------------------------------------------------
|
|
When a device is plugged in it will appear in sysfs as follows::
|
|
|
|
/sys/bus/thunderbolt/devices/0-1/authorized - 0
|
|
/sys/bus/thunderbolt/devices/0-1/device - 0x8004
|
|
/sys/bus/thunderbolt/devices/0-1/device_name - Thunderbolt to FireWire Adapter
|
|
/sys/bus/thunderbolt/devices/0-1/vendor - 0x1
|
|
/sys/bus/thunderbolt/devices/0-1/vendor_name - Apple, Inc.
|
|
/sys/bus/thunderbolt/devices/0-1/unique_id - e0376f00-0300-0100-ffff-ffffffffffff
|
|
|
|
The ``authorized`` attribute reads 0 which means no PCIe tunnels are
|
|
created yet. The user can authorize the device by simply entering::
|
|
|
|
# echo 1 > /sys/bus/thunderbolt/devices/0-1/authorized
|
|
|
|
This will create the PCIe tunnels and the device is now connected.
|
|
|
|
If the device supports secure connect, and the domain security level is
|
|
set to ``secure``, it has an additional attribute ``key`` which can hold
|
|
a random 32-byte value used for authorization and challenging the device in
|
|
future connects::
|
|
|
|
/sys/bus/thunderbolt/devices/0-3/authorized - 0
|
|
/sys/bus/thunderbolt/devices/0-3/device - 0x305
|
|
/sys/bus/thunderbolt/devices/0-3/device_name - AKiTiO Thunder3 PCIe Box
|
|
/sys/bus/thunderbolt/devices/0-3/key -
|
|
/sys/bus/thunderbolt/devices/0-3/vendor - 0x41
|
|
/sys/bus/thunderbolt/devices/0-3/vendor_name - inXtron
|
|
/sys/bus/thunderbolt/devices/0-3/unique_id - dc010000-0000-8508-a22d-32ca6421cb16
|
|
|
|
Notice the key is empty by default.
|
|
|
|
If the user does not want to use secure connect they can just ``echo 1``
|
|
to the ``authorized`` attribute and the PCIe tunnels will be created in
|
|
the same way as in the ``user`` security level.
|
|
|
|
If the user wants to use secure connect, the first time the device is
|
|
plugged a key needs to be created and sent to the device::
|
|
|
|
# key=$(openssl rand -hex 32)
|
|
# echo $key > /sys/bus/thunderbolt/devices/0-3/key
|
|
# echo 1 > /sys/bus/thunderbolt/devices/0-3/authorized
|
|
|
|
Now the device is connected (PCIe tunnels are created) and in addition
|
|
the key is stored on the device NVM.
|
|
|
|
Next time the device is plugged in the user can verify (challenge) the
|
|
device using the same key::
|
|
|
|
# echo $key > /sys/bus/thunderbolt/devices/0-3/key
|
|
# echo 2 > /sys/bus/thunderbolt/devices/0-3/authorized
|
|
|
|
If the challenge the device returns back matches the one we expect based
|
|
on the key, the device is connected and the PCIe tunnels are created.
|
|
However, if the challenge fails no tunnels are created and error is
|
|
returned to the user.
|
|
|
|
If the user still wants to connect the device they can either approve
|
|
the device without a key or write a new key and write 1 to the
|
|
``authorized`` file to get the new key stored on the device NVM.
|
|
|
|
Upgrading NVM on Thunderbolt device or host
|
|
-------------------------------------------
|
|
Since most of the functionality is handled in firmware running on a
|
|
host controller or a device, it is important that the firmware can be
|
|
upgraded to the latest where possible bugs in it have been fixed.
|
|
Typically OEMs provide this firmware from their support site.
|
|
|
|
There is also a central site which has links where to download firmware
|
|
for some machines:
|
|
|
|
`Thunderbolt Updates <https://thunderbolttechnology.net/updates>`_
|
|
|
|
Before you upgrade firmware on a device or host, please make sure it is a
|
|
suitable upgrade. Failing to do that may render the device (or host) in a
|
|
state where it cannot be used properly anymore without special tools!
|
|
|
|
Host NVM upgrade on Apple Macs is not supported.
|
|
|
|
Once the NVM image has been downloaded, you need to plug in a
|
|
Thunderbolt device so that the host controller appears. It does not
|
|
matter which device is connected (unless you are upgrading NVM on a
|
|
device - then you need to connect that particular device).
|
|
|
|
Note an OEM-specific method to power the controller up ("force power") may
|
|
be available for your system in which case there is no need to plug in a
|
|
Thunderbolt device.
|
|
|
|
After that we can write the firmware to the non-active parts of the NVM
|
|
of the host or device. As an example here is how Intel NUC6i7KYK (Skull
|
|
Canyon) Thunderbolt controller NVM is upgraded::
|
|
|
|
# dd if=KYK_TBT_FW_0018.bin of=/sys/bus/thunderbolt/devices/0-0/nvm_non_active0/nvmem
|
|
|
|
Once the operation completes we can trigger NVM authentication and
|
|
upgrade process as follows::
|
|
|
|
# echo 1 > /sys/bus/thunderbolt/devices/0-0/nvm_authenticate
|
|
|
|
If no errors are returned, the host controller shortly disappears. Once
|
|
it comes back the driver notices it and initiates a full power cycle.
|
|
After a while the host controller appears again and this time it should
|
|
be fully functional.
|
|
|
|
We can verify that the new NVM firmware is active by running the following
|
|
commands::
|
|
|
|
# cat /sys/bus/thunderbolt/devices/0-0/nvm_authenticate
|
|
0x0
|
|
# cat /sys/bus/thunderbolt/devices/0-0/nvm_version
|
|
18.0
|
|
|
|
If ``nvm_authenticate`` contains anything other than 0x0 it is the error
|
|
code from the last authentication cycle, which means the authentication
|
|
of the NVM image failed.
|
|
|
|
Note names of the NVMem devices ``nvm_activeN`` and ``nvm_non_activeN``
|
|
depend on the order they are registered in the NVMem subsystem. N in
|
|
the name is the identifier added by the NVMem subsystem.
|
|
|
|
Upgrading NVM when host controller is in safe mode
|
|
--------------------------------------------------
|
|
If the existing NVM is not properly authenticated (or is missing) the
|
|
host controller goes into safe mode which means that the only available
|
|
functionality is flashing a new NVM image. When in this mode, reading
|
|
``nvm_version`` fails with ``ENODATA`` and the device identification
|
|
information is missing.
|
|
|
|
To recover from this mode, one needs to flash a valid NVM image to the
|
|
host controller in the same way it is done in the previous chapter.
|
|
|
|
Networking over Thunderbolt cable
|
|
---------------------------------
|
|
Thunderbolt technology allows software communication between two hosts
|
|
connected by a Thunderbolt cable.
|
|
|
|
It is possible to tunnel any kind of traffic over a Thunderbolt link but
|
|
currently we only support Apple ThunderboltIP protocol.
|
|
|
|
If the other host is running Windows or macOS, the only thing you need to
|
|
do is to connect a Thunderbolt cable between the two hosts; the
|
|
``thunderbolt-net`` driver is loaded automatically. If the other host is
|
|
also Linux you should load ``thunderbolt-net`` manually on one host (it
|
|
does not matter which one)::
|
|
|
|
# modprobe thunderbolt-net
|
|
|
|
This triggers module load on the other host automatically. If the driver
|
|
is built-in to the kernel image, there is no need to do anything.
|
|
|
|
The driver will create one virtual ethernet interface per Thunderbolt
|
|
port which are named like ``thunderbolt0`` and so on. From this point
|
|
you can either use standard userspace tools like ``ifconfig`` to
|
|
configure the interface or let your GUI handle it automatically.
|
|
|
|
Forcing power
|
|
-------------
|
|
Many OEMs include a method that can be used to force the power of a
|
|
Thunderbolt controller to an "On" state even if nothing is connected.
|
|
If supported by your machine this will be exposed by the WMI bus with
|
|
a sysfs attribute called "force_power".
|
|
|
|
For example the intel-wmi-thunderbolt driver exposes this attribute in:
|
|
/sys/bus/wmi/devices/86CCFD48-205E-4A77-9C48-2021CBEDE341/force_power
|
|
|
|
To force the power to on, write 1 to this attribute file.
|
|
To disable force power, write 0 to this attribute file.
|
|
|
|
Note: it's currently not possible to query the force power state of a platform.
|