Re: [PATCH v3 0/6] tpm_crb: Add command and response buffer chunking support

[Jarkko Sakkinen <jarkko@kernel.org>]

On Mon, May 18, 2026 at 08:47:18PM +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]
> 
> This series depends on Jarkko's unmerged patch from the mailing list:
> [PATCH v9 11/11] tpm-buf: Implement managed allocations.
> 
> Depends-on: <http://lore.kernel.org/20260125192526.782202-12-jarkko@kernel.org>

I'll rebase this to the latest master so that it can be included to the
series.

> 
> The whole series applied on top of for-next-tpm branch (with 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/20260506075813.120781-1-armenon@redhat.com/
> 
> 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 (6):
>   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: Implement command and response chunking logic
> 
>  drivers/char/tpm/tpm_crb.c     | 257 +++++++++++++++++++++++++--------
>  drivers/char/tpm/tpm_tis_i2c.c |   6 +-
>  include/linux/tpm.h            |   2 +-
>  3 files changed, 204 insertions(+), 61 deletions(-)
> 
> -- 
> 2.54.0
> 

BR, Jarkko