linux-kernel - Re: [PATCH v6 0/5] Add support for the TPM FF-A start method

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Message-ID: <Z9EkZcX2LmVkNAbq@kernel.org>
Date: Wed, 12 Mar 2025 08:06:29 +0200
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Sudeep Holla <sudeep.holla@....com>
Cc: Stuart Yoder <stuart.yoder@....com>, linux-integrity@...r.kernel.org,
	peterhuewe@....de, jgg@...pe.ca, rafael@...nel.org, lenb@...nel.org,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 0/5] Add support for the TPM FF-A start method

On Tue, Mar 11, 2025 at 03:28:25PM +0000, Sudeep Holla wrote:
> On Mon, Mar 10, 2025 at 01:19:37PM +0200, Jarkko Sakkinen wrote:
> > On Wed, Mar 05, 2025 at 11:36:06AM -0600, Stuart Yoder wrote:
> > > Firmware Framework for Arm A-profile (FF-A) is a messaging framework
> > > for Arm-based systems, and in the context of the TPM CRB driver is used
> > > to signal 'start' to a CRB-based TPM service which is hosted in an
> > > FF-A secure partition running in TrustZone.
> > > 
> > > These patches add support for the CRB FF-A start method defined
> > > in the TCG ACPI specification v1.4 and the FF-A ABI defined
> > > in the Arm TPM Service CRB over FF-A (DEN0138) specification:
> > > https://developer.arm.com/documentation/den0138/latest/
> > > 
> > > The first patch adds an FF-A driver to handle the FF-A messaging when
> > > communicating with a CRB-based TPM secure partition built on FF-A.
> > > The driver is probed when the TPM secure partition is discovered by
> > > the Linux FF-A infrastructure.
> > > 
> > > The second patch consolidates the check for idle support in the CRB
> > > driver to one place.
> > > 
> > > The third patch defines the new ACPI start method enumeration for
> > > CRB over FF-A.
> > > 
> > > The fourth patch adds support for the FF-A ACPI start method to
> > > the TPM crb driver.
> > > 
> > > The fifth patch adds documentation explaining how the CRB driver
> > > and FF-A relate.
> > > 
> > > Version 6
> > > -in tpm_crb removed unnecessary brackets from if statement and
> > >  fixed comment style
> > > -noticed and fixed bug in patch 2, polarity of return value
> > >  from tpm_crb_has_idle() was wrong and wasn't caught in past
> > >  testing
> > > -added Reviewed-by tag to patches 2 and 5
> > > 
> > > Version 5
> > > -tpm_ffa_crb patch: removed module version
> > > -tpm_ffa_crb patch: fixed module description
> > > -tpm_ffa_crb patch: updated comment on mutex declaration
> > > -reworded commit message for patch 2 as per Jarkko's 
> > >  suggestion
> > > -added Acked tag by Sudeep to patch 1 for FF-A changes 
> > > -added Reviewed-by tag to patches 3 and 4
> > > 
> > > Version 4
> > > -fix warning from kernel test robot in patch 1
> > > -fix warnings from checkpatch.pl --strict
> > > -clean up unnecessary parenthesis usage
> > > -update variable declaration to be reverse tree order
> > > -document exported functions in tpm_crb_ffa driver
> > > -remove unnecessary author and maintainer info in tpm_crb_ffa driver
> > > -fix declaration of variables to be in reverse tree order
> > > 
> > > Version 3
> > > -changed prefixes used throughout patch series to tpm_crb_ffa*
> > > 
> > > Version 2
> > > -updates to cover letter to define FF-A
> > > -added new patch with documentation
> > > -created pull request in ACPIA and added link to the patch
> > >  updating actbl3.h
> > > -added tpm_ prefix to the FF-A CRB driver
> > > 
> > > Stuart Yoder (5):
> > >   tpm_crb: implement driver compliant to CRB over FF-A
> > >   tpm_crb: clean-up and refactor check for idle support
> > >   ACPICA: add start method for Arm FF-A
> > >   tpm_crb: add support for the Arm FF-A start method
> > >   Documentation: tpm: add documentation for the CRB FF-A interface
> > > 
> > >  Documentation/security/tpm/tpm_ffa_crb.rst |  65 ++++
> > >  drivers/char/tpm/Kconfig                   |   9 +
> > >  drivers/char/tpm/Makefile                  |   1 +
> > >  drivers/char/tpm/tpm_crb.c                 | 105 +++++--
> > >  drivers/char/tpm/tpm_crb_ffa.c             | 348 +++++++++++++++++++++
> > >  drivers/char/tpm/tpm_crb_ffa.h             |  25 ++
> > >  include/acpi/actbl3.h                      |   1 +
> > >  7 files changed, 535 insertions(+), 19 deletions(-)
> > >  create mode 100644 Documentation/security/tpm/tpm_ffa_crb.rst
> > >  create mode 100644 drivers/char/tpm/tpm_crb_ffa.c
> > >  create mode 100644 drivers/char/tpm/tpm_crb_ffa.h
> > > 
> > > -- 
> > > 2.34.1
> > > 
> > 
> > Check this out:
> > 
> > https://web.git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd.git/log/
> > 
> 
> It is good to get a nod for ACPICA from Rafael as this is not the usual
> pattern. It deviates from normal procedure for ACPICA changes.

There's still time for further reviewing this as I dropped the existing
version:

https://lore.kernel.org/all/Z9EiRDuWfPOkcjXN@kernel.org/

> 
> -- 
> Regards,
> Sudeep


BR, Jarkko