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

[Jarkko Sakkinen <jarkko@kernel.org>]

On Wed, Nov 11, 2026 at 01:57:32AM -0800, Breno Leitao wrote:
> 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>
> 

I think this good stuff so existential condition for having some changes
to address these issues is fulfilled.

I.e. debating the details through will likely lead to productive results
:-)

Br, Jarkko