linux-kernel - Re: [PATCH 3/3] tpm: ibmvtpm: Add support for TPM 2

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Date:   Thu, 13 Feb 2020 13:20:12 -0500
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     Nayna <nayna@...ux.vnet.ibm.com>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        linux-integrity@...r.kernel.org
Cc:     aik@...abs.ru, david@...son.dropbear.id.au,
        linux-kernel@...r.kernel.org, gcwilson@...ux.ibm.com
Subject: Re: [PATCH 3/3] tpm: ibmvtpm: Add support for TPM 2

On 2/13/20 12:53 PM, Nayna wrote:
>
> On 2/4/20 8:27 AM, Stefan Berger wrote:
>> From: Stefan Berger <stefanb@...ux.ibm.com>
>>
>> Support TPM 2 in the IBM vTPM driver. The hypervisor tells us what
>> version of TPM is connected through the vio_device_id.
>>
>> In case a TPM 2 is found, we set the TPM_OPS_AUTO_STARTUP flag to
>> have properly initialize the TPM and driver.
>>
>> Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
>> ---
>>   drivers/char/tpm/tpm_ibmvtpm.c | 8 +++++++-
>>   1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/char/tpm/tpm_ibmvtpm.c 
>> b/drivers/char/tpm/tpm_ibmvtpm.c
>> index eee566eddb35..d479d64a65aa 100644
>> --- a/drivers/char/tpm/tpm_ibmvtpm.c
>> +++ b/drivers/char/tpm/tpm_ibmvtpm.c
>> @@ -29,6 +29,7 @@ static const char tpm_ibmvtpm_driver_name[] = 
>> "tpm_ibmvtpm";
>>
>>   static const struct vio_device_id tpm_ibmvtpm_device_table[] = {
>>       { "IBM,vtpm", "IBM,vtpm"},
>> +    { "IBM,vtpm", "IBM,vtpm20"},
>>       { "", "" }
>>   };
>>   MODULE_DEVICE_TABLE(vio, tpm_ibmvtpm_device_table);
>> @@ -443,7 +444,7 @@ static bool tpm_ibmvtpm_req_canceled(struct 
>> tpm_chip *chip, u8 status)
>>       return (status == 0);
>>   }
>>
>> -static const struct tpm_class_ops tpm_ibmvtpm = {
>> +static struct tpm_class_ops tpm_ibmvtpm = {
>>       .recv = tpm_ibmvtpm_recv,
>>       .send = tpm_ibmvtpm_send,
>>       .cancel = tpm_ibmvtpm_cancel,
>> @@ -672,6 +673,11 @@ static int tpm_ibmvtpm_probe(struct vio_dev 
>> *vio_dev,
>>       if (rc)
>>           goto init_irq_cleanup;
>>
>> +    if (!strcmp(id->compat, "IBM,vtpm20")) {
>> +        chip->flags |= TPM_CHIP_FLAG_TPM2;
>> +        tpm_ibmvtpm.flags = TPM_OPS_AUTO_STARTUP;
>
> TPM_OPS_AUTO_STARTUP flag isn't set for vTPM 1.2. What is different in 
> case of vTPM 2.0 ?


I don't want side effects for the TPM 1.2 case here, so I am only 
modifying the flag for the case where the new TPM 2 is being used.  
Here's the code where it shows the effect.

int tpm_auto_startup(struct tpm_chip *chip)
{
     int rc;

     if (!(chip->ops->flags & TPM_OPS_AUTO_STARTUP))
         return 0;

     if (chip->flags & TPM_CHIP_FLAG_TPM2)
         rc = tpm2_auto_startup(chip);
     else
         rc = tpm1_auto_startup(chip);

     return rc;
}

In the TPM 2 case we then get timeouts, do the TPM self test, send 
TPM2_STARTUP if necessary and get attributes of the TPM 2 command from 
the device. All necessary to start it up.


https://elixir.bootlin.com/linux/latest/source/drivers/char/tpm/tpm2-cmd.c#L719

Does this answer your question ?


    Stefan




>
> Thanks & Regards,
>
>      - Nayna
>