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

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Message-ID: <b424faea-33a7-8e5a-caac-f322fad68118@linux.ibm.com>
Date:   Thu, 13 Feb 2020 14:04:12 -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 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.

static const struct tpm_class_ops tpm_tis = {
     .flags = TPM_OPS_AUTO_STARTUP,
     .status = tpm_tis_status,

https://elixir.bootlin.com/linux/latest/source/drivers/char/tpm/tpm_tis_core.c#L917


>
> 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.


    Stefan


>
> Jason