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

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 11 Sep 2017, Rich Persaud wrote:
> 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

Interesting. In that case, I am OK with keeping "Status: Supported, x86
only".


>                   +### 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.

>From intel_txt.txt, this really seems to be only available on x86
platforms.

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