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

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Message-ID: <20170324101922.mw7vzgesckp26wro@intel.com>
Date:   Fri, 24 Mar 2017 12:19:22 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@....fi>
Cc:     tpmdd-devel@...ts.sourceforge.net,
        linux-security-module@...r.kernel.org,
        Jerry Snitselaar <jsnitsel@...hat.com>, 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 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