Re: [PATCH 3/3] x86/sev: add a SVSM vTPM platform device

Stefano Garzarella
2025-01-23T10:10:03Z

On Thu, Jan 23, 2025 at 11:50:40AM +0200, Jarkko Sakkinen wrote:
>On Wed Jan 22, 2025 at 11:29 PM EET, Dionna Amalie Glaze wrote:
>> I can appreciate this viewpoint. It even surfaced Microsoft's fTPM
>> paper to me, which solves some interesting problems we need to solve
>> in SVSM too. So thanks for that.
>>
>> Just to clarify, you're not asking for SVSM to implement the TIS-MMIO
>> interface instead, but rather to use the fTPM stack, which could make
>> SVSM calls a TEE device operation?
>
>I don't really know what I'm asking because this is barely even a
>PoC, and I state it like this knowingly.
>
>You should make the argument, and the case for the solution. Then
>it is my turn to comment on that scheme.

I'll check if I can use fTPM, in the meantime I had started to simplify
this series, avoiding the double stack and exposing some APIs from SEV
to probe the vTPM and to send the commands. The final driver in
drivers/char/tpm would be quite simple.

But I'll try to see if reusing fTPM is a feasible way, I like the idea.

>
>That said, I would not give high odds for acceptance of a duplicate
>TPM stack succeeding.

Got it ;-)

Thanks to everyone for the helpful feedbacks!

I've been a bit messy these days and I'm in FOSDEM next week, so I hope
not to take too long for the v2.

Stefano