[PATCH 0/2] tpm: Stop retrying TPMs that have stopped working

[Breno Leitao <leitao@debian.org>]

On Meta's datacenter, given the size, TPMs that stop working write about
54 million lines a day to the kernel log, because nothing in the kernel
gives up on them.

Two cases make up nearly all of it.

Some TPMs stop responding. Every command then fails only after the
transport timeout, while the hwrng thread and userspace keep sending
more.

The goal is to retire TPM that are not properly working, similarly to
what was done for EFI in commit 4b2c033b5bc971 ("efi/runtime-wrappers:
retire the worker if a wedged call ever returns")

This feature aim to disable the chip once its commands have kept timing,
instead of keeping it in this desolate state.

Disabling the chip makes the failure explicit: the log gets one line
saying the TPM is disabled, and every later command fails at once
instead of timing out. 

A health-check daemon, such as machine checker, can then detect
the broken hardware and send the machine to repair.

Signed-off-by: Breno Leitao <leitao@debian.org>
---
Breno Leitao (2):
      tpm: Disable a TPM that stops responding
      tpm: Disable a TPM whose hwrng reads keep failing

 drivers/char/tpm/tpm-chip.c      | 20 +++++++++++++++++++-
 drivers/char/tpm/tpm-interface.c | 29 +++++++++++++++++++++++++++++
 include/linux/tpm.h              |  3 +++
 3 files changed, 51 insertions(+), 1 deletion(-)
---
base-commit: 630059a5a632377b9b7b487baccde92b7ae1dd47
change-id: 20261110-tpm_unresponsive-a5f71c1db026

Best regards,
--  
Breno Leitao <leitao@debian.org>