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

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Message-ID: <698be72a53ede_8c321007f@dwillia2-mobl4.notmuch>
Date: Tue, 10 Feb 2026 18:19:22 -0800
From: <dan.j.williams@...el.com>
To: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	Dan Williams <dan.j.williams@...el.com>, "Kirill A . Shutemov"
	<kas@...nel.org>
CC: Dave Hansen <dave.hansen@...ux.intel.com>, Rick Edgecombe
	<rick.p.edgecombe@...el.com>, <x86@...nel.org>,
	<linux-kernel@...r.kernel.org>, <linux-coco@...ts.linux.dev>
Subject: Re: [PATCH v1 3/3] virt: tdx-guest: Increase Quote buffer size to
 128KB

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@...el.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> ---
>  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"