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 <j...@freebsd.org>. John Baldwin, j...@freebsd.org 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."
