virt: tdx-guest: Make the Quote buffer size dynamic

Support a new TDX module ABI that reports the Quote size limit in a
metadata field. The fixed 128KB buffer in the driver may be too small
for Quotes that use new algorithms like post-quantum cryptography (PQC),
which can produce much larger certificates. With this ABI, the guest
sizes the buffer to the platform's needs and no longer has to rely on
some empirical number.

The shared buffer comes from the buddy allocator, as the host expects it
to be physically contiguous. The allocator's page order limit should be
sufficient for current attestation needs. Platforms that don't report
the limit fall back to the default 128KB buffer.

Assume the TDX module always reports the same size. It is a TDX module
bug if the size changes.

AI was used under supervision to collect/apply feedback, review code and
workshop logs.

Based on a patch originally by Kuppuswamy Sathyanarayanan.

Signed-off-by: Peter Fang <peter.fang@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Link: https://patch.msgid.link/20260930103739.2851980-7-peter.fang@intel.com

0 files changed, 0 insertions, 0 deletions