Re: [PATCH v8 5/5] x86/tdx: Add Quote generation support

Dave Hansen
2022-07-21T17:04:55Z

On 7/21/22 09:54, Sathyanarayanan Kuppuswamy wrote:
>
> On 7/21/22 9:49 AM, Dave Hansen wrote:
>> On 7/21/22 09:42, Sathyanarayanan Kuppuswamy wrote:
>>> On 7/21/22 9:08 AM, Dave Hansen wrote:
>>>> On 6/8/22 19:52, Kuppuswamy Sathyanarayanan wrote:
>>>>> For shared buffer allocation, alternatives like using the DMA API is
>>>>> also considered. Although it simpler to use, it is not preferred because
>>>>> dma_alloc_*() APIs require a valid bus device as argument, which would
>>>>> need converting the attestation driver into a platform device driver.
>>>>> This is unnecessary, and since the attestation driver does not do real
>>>>> DMA, there is no need to use real DMA APIs.
>>>> Let's actually try to walk through the requirements for the memory
>>>> allocation here.
>>>>
>>>> 1. The guest kernel needs to allocate some guest physical memory
>>>> for the attestation data buffer
>>> Physically contiguous memory.
>> Remind me how large the quote structures are.
> It depends on the attestation service. In addition to TDREPORT (1K size),
> during quote generation, additional data can be included in the signed
> quote. So the spec allows variable length. User agent will communicate with
> attestation service to identify the appropriate buffer length. Our test
> uses 8K buffers

What is this "additional data"? Is that "REPORTDATA" from the TDX
module spec?

"Additional REPORTDATA, a 64-byte value, is provided by the
guest TD to be included in the TDG.MR.REPORT."