[RFC v2 0/7] hw/tpm: CRB chunking capability to handle PQC

[Arun Menon <armenon@redhat.com>]

The move to Post Quantum Cryptography (PQC) changes how we manage
memory buffers. Unlike classic crypto algorithms like RSA or ECC which
used small keys and signatures, PQC algorithms require larger buffers.

The new version of TCG TPM v185 (currently under review [1]) supports
sending data/commands in chunks for the CRB (Command Response Buffer)
interface. This is in line with the initiative to support PQC algorithms.

This series implements the logic to send and receive data from the
linux guest to the TPM backend in chunks, thereby allowing the
guest to send larger data buffers. We introduce 2 new control registers
called nextChunk and crbRspRetry that will control the START. We also
add the CRB Interface Identifier called CapCRBChunk that is set to 1
indicating that the device supports chunking. The default maximum
chunk/buffer size is 3968 (4096 - 128) bytes.

During a send operation, the guest driver places data in the CRB buffer
and signals nextChunk for each segment until the final chunk is reached.
Upon receiving the START signal, QEMU appends the final chunk to its
internal buffer and dispatches the complete command to the TPM backend.

For responses, the backend's output is buffered. The guest consumes the
first chunk once the START bit is cleared. Subsequent chunks are
retrieved by the guest toggling the nextChunk bit, which advances the
internal buffer offset and populates the CRB data window.

For this to work, the linux guest tpm driver will also have to
a) probe if CRB chunking is supported
b) send data in chunks if the command length exceeds the chunk size.
c) receive data in chunks by sending a nextChunk signal and accumulate.

The included test demonstrates functional correctness for standard
buffer sizes. However, validation of PQC-sized payloads was performed
via manual buffer-size overrides.

[1] https://trustedcomputinggroup.org/wp-content/uploads/PC-Client-Specific-Platform-TPM-Profile-for-TPM-2p0-v1p07_rc1_121225.pdf

v2
--
- Add the VM migration support.
- Increase the TIS TPM interface max buffer size to 8192.

Arun Menon (7):
  hw/tpm: Add TPM CRB chunking fields
  hw/tpm: Refactor CRB_CTRL_START register access
  hw/tpm: Add internal buffer state for chunking
  hw/tpm: Implement TPM CRB chunking logic
  test/qtest: Add test for tpm crb chunking
  hw/tpm: Add support for VM migration with TPM CRB chunking
  hw/tpm: Increase TPM TIS max buffer size to 8192

 hw/core/machine.c                |   1 +
 hw/tpm/tpm_crb.c                 | 291 ++++++++++++++++++++++++++++---
 hw/tpm/tpm_tis.h                 |   2 +-
 include/hw/acpi/tpm.h            |   5 +-
 tests/qtest/tpm-crb-swtpm-test.c |  10 ++
 tests/qtest/tpm-util.c           | 106 +++++++++--
 tests/qtest/tpm-util.h           |   5 +
 7 files changed, 382 insertions(+), 38 deletions(-)

-- 
2.53.0