Re: [Xen-devel] [PATCH RFC] Add SUPPORT.md

[Rich Persaud <persaur@xxxxxxxxx>]

On Sep 11, 2017, at 10:16, George Dunlap <george.dunlap@xxxxxxxxxx> wrote:

+### vTPM Support

+

+    Status: Supported, x86 only

This should probably be x86/vTPM. TPM, the way we are discussing it, is

an x86-only implementation. ARM-based alternatives are not called TPM

AFAIK.

Someone said that because this was implemented entirely in userspace,
there's no reason the PV TPM couldn't work on ARM.  OTOH I suppose it
would be a lot less valuable if there weren't a physical TPM to back it up.

Any thoughts on that?

Physical TPMs are present on both x86 and ARM Chromebooks:

  https://www.chromium.org/developers/design-documents/tpm-usage

e.g. see Step 9 in this Samsung Series 3 teardown, "Infineon SLB9635":

  https://www.ifixit.com/Teardown/Samsung+Chromebook+Series+3+Teardown/12225

+### Intel/TXT ???

Same here

Well unless someone actually says something about this I'm just going go
delete it.

That's one way to motivate a response :)

Slide 11 of Joe Cihula's 2007 presentation documents the Xen changes for TXT: 

  http://www-archive.xenproject.org/files/xensummit_fall07/23_JosephCihula.pdf

More info in the 2007 patch and the Linux kernel doc:

  http://old-list-archives.xen.org/archives/html/xen-devel/2007-10/msg00897.html

  https://www.kernel.org/doc/Documentation/intel_txt.txt

Intel TXT is used with Xen by (at least) Qubes, OpenXT and Skyport Systems.  There was a design discussion at Xen Summit about implementing a frequently-used subset of tboot logic in Xen.  Hopefully Intel TXT will continue to be a Xen feature with security support.

Rich

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