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

From: Jerry Snitselaar
Date: Sat Mar 25 2017 - 08:29:19 EST



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@xxxxxxxxxxxxxxx>
>> ---
>> 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.