[RFC PATCH v2 0/4] tsm: Runtime measurement registers ABI

Samuel Ortiz
2024-01-28T21:27:10Z

Some confidential computing architectures (Intel TDX, ARM CCA, RISC-V
CoVE) provide their guests with a set of measurements registers that can
be extended at runtime, i.e. after the initial, host-initiated
measurements of the TVM are finalized. Those runtime measurement
registers (RTMR) are isolated from the host accessible ones but TSMs
include them in their signed attestation reports.

All architectures supporting RTMRs expose a similar interface to their
TVMs: An extension command/call that takes a measurement value and an
RTMR index to extend it with, and a readback command for reading an RTMR
value back (taking an RTMR index as an argument as well). This patch series
builds an architecture agnostic, configfs-based ABI for userspace to extend
and read RTMR values back. It extends the current TSM ops structure and
each confidential computing architecture can implement this extension to
provide RTMR support.

Changes since v1 [1]:
- Removed the abilty for userspace to configure the TCG PCR mappings. The
configfs attribute for the TCG PCR mapping is now RO, and the mapping is
passed from the TSM provider as a static bitmap.
- Document the added tsm-configs attributes.

TODO:

- Event log support.

[1] https://lore.kernel.org/lkml/20240114223532.290550-1-sameo@rivosinc.com/

---

Samuel Ortiz (4):
tsm: Runtime measurement register support
tsm: Add RTMRs to the configfs-tsm hierarchy
tsm: Map RTMRs to TCG TPM PCRs
tsm: Allow for extending and reading configured RTMRs

Documentation/ABI/testing/configfs-tsm | 36 +++
drivers/virt/coco/Kconfig | 1 +
drivers/virt/coco/tsm.c | 376 +++++++++++++++++++++++++
include/linux/tsm.h | 39 ++-
4 files changed, 451 insertions(+), 1 deletion(-)

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2.42.0