Joseph Mayer wrote this message on Sat, Mar 21, 2020 at 02:57 +0000:
Thunderbolt support would be awesome. Especially it would allow the use
of additional M.2 NVMe SSD:s on a laptop at full performance.
Thunderbolt support would also allow the use of an AMDGPU via a PCIe
chassi, as well as enable the use of 10gbps Ethernet on laptops [1].
While I like to use Thunderbolt for this pragmatic reason, also Intel
apparently promises license etc. generosity to computer makers, which
certainly does not hurt. [2]
FreeBSD has Thunderbolt support. It appears to me that they call it
"PCIe Hot plug". [3]
From my understanding, Thunderbolt is different from PCIe Hot Plug...
PCIe the spec itself has hot plug capabilities, and this is what is
used for laptops w/ ExpressCards and some servers...
Thunderbolt from my understanding is more complicated due to
display routing and other related features and FreeBSD does NOT
yet have support for it.
It was implemented 2015 by John-Mark Gurney [email protected].
John Baldwin,[email protected] ended up implementing it differently
and not using the code I had written, so he is probably a better
person to ask on the current state of the code..
This was done via:
https://reviews.freebsd.org/D6136?id=15683
I have heard that there may be a proper ThunderBolt support coming
to FreeBSD in the near future, but not sure exactly when...
Not sure if a TB device must be attached on boot and cannot be
detached, anyhow if that is the case then still totally fine.
The devctl command can detach a device. This allows ejecting
devices w/o crashing the system for removal, or allowing you to detach
a device and pass it through to a bhyve vm, etc. Not all drivers are
written to allow detaching...
NetBSD appears to have support also but I don't find details.
Security-wise Thunderbolt without IOMMU is correlated with physical
break-in attack vectors, anyhow that is commonly fine. [4]
From my understanding, all PCIe switches have a built in IOMMU, so
this shouldn't be a major security issue. I have not done indepth
analysis to verify this though. and this also depends upon the
PCIe switch not having bugs...
There is a relatively inexpensive USB3 to PCIe bridge that lets you
issue arbitrary PCIe commands that could be used to verify the security
of implementations...
One Thunderbolt 3 controller provides 22gbps of PCIe data bandwidth to
all the one or two Thunderbolt ports it exports, which is fine. [5]
Many Thunderbolt devices allow daisy chaining. An "eGFX" certified [6]
Thunderbolt PCIe chassi (such as [7]) has absolutely no performance
advantage over a normal Thunderbolt PCIe chassi (such as [8]),
including for eGPU (e.g. AMDGPU) use.
Good luck!
[1] The lowest cost and most common 10gbps Ethernet Thunderbolt chip
is Aquantia AQC107S. There are also some adapters based on a normal
PCIe 10gbps chip and a separate Thunderbolt to PCIe controller.
[2] https://www.theregister.co.uk/2017/05/24/intel_thunderbolt_3forall/
[3]
https://www.freebsd.org/news/status/report-2015-01-2015-03.html#Adding-PCIe-Hot-plug-Support
https://www.freebsd.org/news/status/report-2015-07-2015-09.html#Adding-PCIe-Hot-plug-Support
[4]
https://www.osnews.com/story/129501/thunderbolt-enables-severe-security-threats/
[5] And not 40gbps as common marketing makes it sound like.
[6] https://thunderbolttechnology.net/egfx
https://thunderbolttechnology.net/blog/the-difference-between-egfx-and-egpu
= marketing mumbo jumbo.
[7] https://www.asus.com/Graphics-Cards-Accessories/XG-STATION-PRO/
[8] https://www.akitio.com/expansion/node-pro
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
