[RFC v2 0/5] tpm_crb: Add command and response buffer chunking support

[Arun Menon <armenon@redhat.com>]

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 larger TPM
cmd/rsp between the linux guest and the TPM backend in chunks.
Currently, the TPM CRB driver is limited by the physical size of the
MMIO window. When userspace attempts to send a payload that exceeds this
size, the driver rejects it.

This series introduces chunking support. The driver now checks the CRB
interface capability for CRB_INTF_CAP_CRB_CHUNK. If supported by the
backend, the driver will slice oversized commands into MMIO-sized
chunks, signalling the backend via CRB_START_NEXT_CHUNK, and finalizing
with CRB_START_INVOKE. Responses are also read back in a similar chunked
manner.

If the backend does not support chunking, the driver retains its legacy
behaviour and enforces the standard size limits.

This feature also requires the QEMU to interpret the data in chunks and
forward it to the TPM backend and subsequently dispatch the TPM response
in chunks back to the linux guest. This is implemented in [2]

[1] https://trustedcomputinggroup.org/wp-content/uploads/PC-Client-Specific-Platform-TPM-Profile-for-TPM-2p0-v1p07_rc1_121225.pdf
[2] https://lore.kernel.org/qemu-devel/20260319135316.37412-1-armenon@redhat.com/

v2
--
- Add size checks before copying memory.
- Update TPM_BUFSIZE to 8KB.
- Commit messages updated to indicate motivation and logic of the change.

Arun Menon (5):
  tpm_crb: Add register definitions of TPM CRB chunking fields
  tpm_crb: Add new wrapper function to invoke start method
  tpm_crb: Implement command and response chunking logic
  tpm: Increase TPM_BUFSIZE to 8kB for chunking support
  tpm: tis_i2c: Use local 4KB buffer to limit memory usage

 drivers/char/tpm/tpm.h         |   2 +-
 drivers/char/tpm/tpm_crb.c     | 199 +++++++++++++++++++++++----------
 drivers/char/tpm/tpm_tis_i2c.c |   6 +-
 3 files changed, 146 insertions(+), 61 deletions(-)

-- 
2.53.0