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

[Jarkko Sakkinen <jarkko@kernel.org>]

On Thu, Nov 12, 2026 at 12:30:35AM +0200, Jarkko Sakkinen wrote:
> 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
> :-)

$ tpm2sh return-code 256
TPM_RC_INITIALIZE

I.e. TPM has not been properly initialized by TPM2_Startup().

I.e. TPM is also saying that it is *disabled*.

So acting on this proven fact  makes most sense to me.

Br, Jarkko