Re: [PATCH v5 0/7] tpm_crb: Add command and response buffer chunking support

[Jarkko Sakkinen <jarkko@kernel.org>]

On Thu, Oct 29, 2026 at 11:45:34PM +0530, Arun Menon wrote:
> The new version of TCG TPM v185 [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] and
> already merged into the mainline.
> 
> The whole series applied on top of for-next-tpm (including prerequisite)
> can be found here:
> https://github.com/armenon-rh/linux/tree/tpm-crb-linux
> 
> [1] https://trustedcomputinggroup.org/wp-content/uploads/PC-Client-Specific-Platform-TPM-Profile-for-TPM-2p0-v1p07_Pub.pdf
> [2] https://lore.kernel.org/qemu-devel/20260601215410.517009-1-stefanb@linux.ibm.com/
> 
> v5
> --
> - Split [PATCH v4 06/06] into 2. The preparation patch separates the
>   no-chunking send() and recv() from chunking.
> - Fixed block comments to respect kernel's preferred multi-line style.
> - Added citations to the TCG TPM and NIST FIPS documentations. Explained
>   the logic and newly introduced registers in brief in the git commit
>   message.
> 
> v4
> --
> - Rebased on master (or for-next-tpm, both point to the same commit).
> - Resolved one conflict in PATCH v3 05/06, as TPM_BUFSIZE is declared in
>   include/linux/tpm_command.h.
> 
> v3
> --
> - Split patch 2, so that the code is cleaner.
> - Re-order the buffer size adjustment patch.
> - Rename crb_trigger_tpm to tpm_crb_start.
> - Add dispatching logic in send and recv functions. Chunking is
>   separated from no-chunking for clarity.
> - Increase TPM_BUFSIZE in the common file include/linux/tpm.h following,
>   [PATCH v9 11/11] tpm-buf: Implement managed allocations
>   https://lore.kernel.org/linux-integrity/20260125192526.782202-12-jarkko@kernel.org/
> 
> 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 (7):
>   tpm_crb: Add register definitions of TPM CRB chunking fields
>   tpm_crb: Split start method into a separate header
>   tpm_crb: Add start_cmd parameter to tpm_crb_start wrapper
>   tpm: tis_i2c: Use local 4KB buffer to limit memory usage
>   tpm: Increase TPM_BUFSIZE to 8KB for chunking support
>   tpm_crb: Factor crb_send()/crb_recv() bodies into helpers
>   tpm_crb: Implement command and response chunking logic
> 
>  drivers/char/tpm/tpm_crb.c     | 226 +++++++++++++++++++++++++++------
>  drivers/char/tpm/tpm_tis_i2c.c |   6 +-
>  include/linux/tpm_command.h    |   2 +-
>  3 files changed, 189 insertions(+), 45 deletions(-)
> 
> -- 
> 2.56.0
> 

Applied, thank you.

Br, Jarkko