Re: [PATCH v1 3/3] virt: tdx-guest: Increase Quote buffer size to 128KB

[dan.j.williams]

Kuppuswamy Sathyanarayanan wrote:
> Intel platforms are transitioning from traditional SGX-based
> attestation toward DICE-based attestation as part of a broader move
> toward open and standardized attestation models. DICE enables layered
> and extensible attestation, where evidence is accumulated across
> multiple boot stages.
> 
> With SGX-based attestation, Quote sizes are typically under 8KB, as the
> payload consists primarily of Quote data and a small certificate bundle.
> Existing TDX guest code sizes the Quote buffer accordingly.
> 
> DICE-based attestation produces significantly larger Quotes due to the
> inclusion of evidence (certificate chains) from multiple boot layers.
> The cumulative Quote size can reach approximately 100KB.
> 
> Increase GET_QUOTE_BUF_SIZE to 128KB to ensure sufficient buffer
> capacity for DICE-based Quote payloads.
> 
> Reviewed-by: Fang Peter <peter.fang@xxxxxxxxx>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> ---
>  Documentation/ABI/testing/configfs-tsm-report | 4 ++++
>  drivers/virt/coco/tdx-guest/tdx-guest.c       | 4 +++-
>  2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/ABI/testing/configfs-tsm-report b/Documentation/ABI/testing/configfs-tsm-report
> index ca3352cfd2f1..7a6a5045a7d5 100644
> --- a/Documentation/ABI/testing/configfs-tsm-report
> +++ b/Documentation/ABI/testing/configfs-tsm-report
> @@ -73,6 +73,10 @@ Description:
>  		Library Revision 0.8 Appendix 4,5
>  		https://download.01.org/intel-sgx/latest/dcap-latest/linux/docs/Intel_TDX_DCAP_Quoting_Library_API.pdf
>  
> +		Intel TDX platforms with DICE-based attestation use CBOR Web Token
> +		(CWT) format for the Quote payload. This is indicated by the Quote
> +		size exceeding 8KB.

Looks ok, please follow up with a link to the full format specification
when it is published.

I will change this subject to:

"configfs-tsm-report: tdx_guest: Increase Quote buffer size to 128KB"