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

[Stefan Berger]

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.


ÂÂ Stefan


> Jason