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/[email protected]/ Arun Menon (4): tpm_crb: Add definition 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 64kB for chunking support drivers/char/tpm/tpm.h | 2 +- drivers/char/tpm/tpm_crb.c | 194 ++++++++++++++++++++++++++----------- 2 files changed, 137 insertions(+), 59 deletions(-) -- 2.53.0
