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

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Message-ID: <20200213193908.GP31668@ziepe.ca>
Date:   Thu, 13 Feb 2020 15:39:08 -0400
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Stefan Berger <stefanb@...ux.ibm.com>
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 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.

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

Jason