Re: SVSM Attestation and vTPM specification additions - v0.60

[Tom Lendacky <thomas.lendacky@amd.com>]

On 1/24/23 03:45, Jörg Rödel wrote:
> On Tue, Jan 10, 2023 at 12:54:27PM -0600, Tom Lendacky wrote:
>> Attached is an updated draft version of the SVSM specification with added
>> support for an attestation protocol and a vTPM protocol as well as other
>> miscellaneous changes (all identified by change bar). Please take a look and
>> reply with any feedback you may have.
> 
> Another addition I'd like to propose:
> 
> It would be nice to have a protocol number reserved for implementation
> specific requests. The protocol number only defines one standardized
> request to identify the specific SVSM implemenation in use. Other
> requests are implementation specific and can be used to manage the SVSM
> from the guest.

Would returning an implementation GUID as part of SVSM_CORE_QUERY_PROTCOL 
or adding a SVSM_CORE_GET_IMPLEMENTATION call to the core protocol be 
better? Then we could reserve a range of protocols for use SVSM 
implementation specific protocols as opposed to just one. Since the 
protocol ID is 32-bits, maybe make 0x8000_0000 to 0x8FFF_FFFF be SVSM 
implementation specific.

Which would folks prefer? A new protocol to retrieve the implementation, 
modify SVSM_CORE_QUERY_PROTCOL or add SVSM_CORE_GET_IMPLEMENTATION to the 
core protocol?

Or any strong feelings about why this wouldn't be good?

Thanks,
Tom

> 
> One use-case would be, for example, to read the SVSM log buffer from the
> guest side, but depending on the implementation there could be more
> requests defined.
> 
> Regards,
>