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

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Date:   Thu, 13 Feb 2020 14:45:49 -0500
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     Nayna <nayna@...ux.vnet.ibm.com>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        linux-integrity@...r.kernel.org, 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 2:39 PM, Jason Gunthorpe wrote:
> On Thu, Feb 13, 2020 at 02:15:03PM -0500, Stefan Berger wrote:
>> On 2/13/20 2:11 PM, Jason Gunthorpe wrote:
>>> On Thu, Feb 13, 2020 at 02:04:12PM -0500, Stefan Berger wrote:
>>>> On 2/13/20 1:35 PM, Jason Gunthorpe wrote:
>>>>> On Thu, Feb 13, 2020 at 01:20:12PM -0500, Stefan Berger wrote:
>>>>>
>>>>>> 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.
>>>>> I'm surprised this driver is using AUTO_STARTUP, it was intended for
>>>>> embedded cases where their is no firmware to boot the TPM.
>>>> The TIS is also using it on any device.
>>> TIS is a generic driver, and can run on TPMs without firmware
>>> support. It doesn't know either way
>> The following drivers are all using it:
>>
>>
>> drivers/char/tpm/st33zp24/st33zp24.c, line 493
>> drivers/char/tpm/tpm-interface.c, line 374
>> drivers/char/tpm/tpm_crb.c, line 421
>> drivers/char/tpm/tpm_ftpm_tee.c, line 184
>> drivers/char/tpm/tpm_i2c_atmel.c, line 139
>> drivers/char/tpm/tpm_i2c_infineon.c, line 602
>> drivers/char/tpm/tpm_i2c_nuvoton.c, line 465
>> drivers/char/tpm/tpm_tis_core.c, line 917
>> drivers/char/tpm/tpm_vtpm_proxy.c, line 435
>>
>> https://elixir.bootlin.com/linux/latest/ident/TPM_OPS_AUTO_STARTUP
> These are all general purpose drivers.
>
> Though perhaps vtpm_proxy shouldn't include it, not sure.
>
>>>>> Chips using AUTO_STARTUP are basically useless for PCRs/etc.
>>>>>
>>>>> I'd expect somthing called vtpm to have been started and PCRs working
>>>>> before Linux is started??
>>>> Yes, there's supposed to be firmware.
>>>>
>>>> I only see one caller to tpm2_get_cc_attrs_tbl(chip), which is necessary to
>>>> call. This caller happens to be in tpm2_auto_startup.
>>> That seems to be a mistake, proper startup of the driver should never
>>> require auto_startup.
>> Is this IBM vTPM driver special that it should do things differently than
>> all those drivers listed above? From looking at the code is seems it is to
>> be set for the TPM 2.0 case.
> Any driver that knows the TPM must be started prior to Linux
> booting should not use the flag.  vtpm drivers in general would seem
> to be the case where we can make this statement.

Wouldn't this statement apply to all systems, including embedded ones?  
Basically all firmwares should implement the CRTM and do the TPM 
initialization.


>
> If it was mandatory then it would not be a flag the driver has to specify.

I'll add a case where we call into  tpm2_get_cc_attrs_tbl(chip) in case 
the auto startup flag is not set. I believe this is the only part that's 
missing for TPM 2 to work if not autostarted.


    Stefan


>
> Jason