linux-kernel - Re: [PATCH v4] tpm_crb: request and relinquish locality 0

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Message-ID: <20170325195047.i7ljllr7p7osl4lv@intel.com>
Date:   Sat, 25 Mar 2017 21:50:47 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Jerry Snitselaar <jsnitsel@...hat.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@....fi>,
        tpmdd-devel@...ts.sourceforge.net,
        linux-security-module@...r.kernel.org, gang.wei@...el.com,
        Peter Huewe <peterhuewe@....de>,
        Marcel Selhorst <tpmdd@...horst.net>,
        Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] tpm_crb: request and relinquish locality 0

On Sat, Mar 25, 2017 at 05:21:30AM -0700, Jerry Snitselaar wrote:
> 
> Jarkko Sakkinen @ 2017-03-24 10:19 GMT:
> 
> > On Fri, Mar 24, 2017 at 12:10:30PM +0200, Jarkko Sakkinen wrote:
> >> This commit adds support for requesting and relinquishing locality 0 in
> >> tpm_crb for the course of command transmission.
> >> 
> >> In order to achieve this, two new callbacks are added to struct
> >> tpm_class_ops:
> >> 
> >> - request_locality
> >> - relinquish_locality
> >> 
> >> With CRB interface you first set either requestAccess or relinquish bit
> >> from TPM_LOC_CTRL_x register and then wait for locAssigned and
> >> tpmRegValidSts bits to be set in the TPM_LOC_STATE_x register.
> >> 
> >> The reason why were are doing this is to make sure that the driver
> >> will work properly with Intel TXT that uses locality 2. There's no
> >> explicit guarantee that it would relinquish this locality. In more
> >> general sense this commit enables tpm_crb to be a well behaving
> >> citizen in a multi locality environment.
> >> 
> >> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> >> ---
> >> v2:
> >> - TPM driver level calllbacks
> >> v3:
> >> - Call ops->relinquish_locality only if ops->request_locality has been
> >>   successful.
> >> - Do not reserve locality in nested tpm_transmit calls.
> >> - Check for tpmRegValidSts to make sure that the value in TPM_LOC_STATE_x is
> >>   stable.
> >> v4:
> >> - Removed tpm_tis_core changes. It needs to be done separately. It will be
> >>   postponed to 4.13.
> >> - Store locality to struct tpm_chip while active.
> >>  drivers/char/tpm/tpm-chip.c      |  1 +
> >>  drivers/char/tpm/tpm-interface.c | 13 +++++++++++++
> >>  drivers/char/tpm/tpm.h           |  3 +++
> >>  drivers/char/tpm/tpm_crb.c       | 41 ++++++++++++++++++++++++++++++++++++++++
> >>  include/linux/tpm.h              |  3 ++-
> >>  5 files changed, 60 insertions(+), 1 deletion(-)
> >> 
> >> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> >> index aade699..a321bd5 100644
> >> --- a/drivers/char/tpm/tpm-chip.c
> >> +++ b/drivers/char/tpm/tpm-chip.c
> >> @@ -231,6 +231,7 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
> >>  		goto out;
> >>  	}
> >>  
> >> +	chip->locality = -1;
> >>  	return chip;
> >>  
> >>  out:
> >> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> >> index 95c6f98..1815666 100644
> >> --- a/drivers/char/tpm/tpm-interface.c
> >> +++ b/drivers/char/tpm/tpm-interface.c
> >> @@ -384,6 +384,7 @@ ssize_t tpm_transmit(struct tpm_chip *chip, struct tpm_space *space,
> >>  	ssize_t len = 0;
> >>  	u32 count, ordinal;
> >>  	unsigned long stop;
> >> +	bool need_locality = chip->locality == -1;
> >
> > This must be set *after* taking the mutex. Otherwise, I think this
> > should be fine now.
> >
> > /Jarkko
> 
> Sorry, I missed this email earlier. Yeah, I ran into this while trying to get the
> tpm_tis code working with this change tonight. Are you just going to move the
> assignment to right before the if block for request_locality? I've
> tested with the assignment moved inside the mutex on a kabylake
> system.
> 
> I also tested with a patch for adding support to tpm_tis on a tpm_tis
> system, but that is a work in progress.

Yes. It's like that now in the locality branch in my tree.

/Jarkko