[v2,0/4] tpm: add support for sync send() and use it in ftpm and svsm drivers

Message

Stefano Garzarella April 8, 2025, 8:32 a.m. UTC

This series is a follow-up to the discussion we had about whether or not
to add send_recv() op in tpm_class_ops[1]. Much boilerplate code has
already been removed by Jarkko with commit 980a573621ea ("tpm: Make
chip->{status,cancel,req_canceled} opt"). With this series we try to
avoid also the temporary buffers needed between send() and recv() for
devices that do not support interrupts and provide a single operation
to send the command and receive the response on the same buffer like
tpm_ftpm_tee.

The biggest advantage for this approach is with tpm_ftpm_tee where we
remove the local buffer and extra memory copies. For tpm_svsm it does
not change much since we continue to use the pre-allocated buffer,
to avoid making an allocation for each command.

Introduce a new flag (TPM_CHIP_FLAG_SYNC) to support synchronous send().
If that flag is set by the driver, tpm_try_transmit() will use the send()
callback to send the command and receive the response on the same buffer
synchronously. In that case send() return the number of bytes of the
response on success, or -errno on failure.

This series is based on "[PATCH v6 0/4] Enlightened vTPM support for SVSM
on SEV-SNP" [2], so if we want to apply this series first, we just have to
remove a hunk in the first patch and the whole last patch.

I removed Jens' T-b and Sumit R-b from RFC/v1 since we changed the code a
bit, so I kindly ask if you can test/review again.
I left some questions on patch 1.

Thanks,
Stefano

Changelog
- v1 -> v2
  - changed title since we removed send_recv() op
  - implemented TPM_CHIP_FLAG_SYNC idea [Jarkko]
  - removed Jens' T-b

- RFC -> v1: https://lore.kernel.org/linux-integrity/[e-mail]/
  - added Jens' T-b on ftpm driver
  - removed last patch since [2] is not yet merged and will require a new version

- RFC: https://lore.kernel.org/linux-integrity/[e-mail]/

[1] https://lore.kernel.org/linux-integrity/[e-mail]/
[2] https://lore.kernel.org/linux-integrity/[e-mail]/

Stefano Garzarella (4):
  tpm: add buf_size parameter in the .send callback
  tpm: support devices with synchronous send()
  tpm/tpm_ftpm_tee: support TPM_CHIP_FLAG_SYNC
  tpm/tpm_svsm: support TPM_CHIP_FLAG_SYNC

 drivers/char/tpm/tpm_ftpm_tee.h      |  4 --
 include/linux/tpm.h                  |  4 +-
 drivers/char/tpm/st33zp24/st33zp24.c |  2 +-
 drivers/char/tpm/tpm-interface.c     | 20 +++++++--
 drivers/char/tpm/tpm_atmel.c         |  3 +-
 drivers/char/tpm/tpm_crb.c           |  2 +-
 drivers/char/tpm/tpm_ftpm_tee.c      | 66 +++++++++-------------------
 drivers/char/tpm/tpm_i2c_atmel.c     |  3 +-
 drivers/char/tpm/tpm_i2c_infineon.c  |  3 +-
 drivers/char/tpm/tpm_i2c_nuvoton.c   |  3 +-
 drivers/char/tpm/tpm_ibmvtpm.c       |  6 ++-
 drivers/char/tpm/tpm_infineon.c      |  3 +-
 drivers/char/tpm/tpm_nsc.c           |  3 +-
 drivers/char/tpm/tpm_svsm.c          | 28 +++++-------
 drivers/char/tpm/tpm_tis_core.c      |  3 +-
 drivers/char/tpm/tpm_tis_i2c_cr50.c  |  6 ++-
 drivers/char/tpm/tpm_vtpm_proxy.c    |  4 +-
 drivers/char/tpm/xen-tpmfront.c      |  3 +-
 18 files changed, 81 insertions(+), 85 deletions(-)


base-commit: 92d2673cb03c16e47d7308dedad6ff3bc3d117ca