Re: [PATCH] tpm_tis: Issue a TPM2_Shutdown for TPM2 devices.

[Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>]

On Fri, Apr 28, 2017 at 02:32:31PM -0700, Josh Zimmerman wrote:
> On Fri, Apr 28, 2017 at 11:43 AM, Jason Gunthorpe
> <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> wrote:
> > On Fri, Apr 28, 2017 at 11:27:16AM -0700, Josh Zimmerman wrote:
> >> It sounds like there are several intertwined issues here. I'd like to
> >> keep this patch relatively minimal, so here are my current thoughts on
> >> a path forward:
> >>
> >> * Refactor references to chip->ops to go through tpm_try_get_ops, as
> >> mentioned in the previous patch
> >
> > As I said, if you rely on the fact that sysfs does not exist for TPM2
> > then this should already be done for the TPM2 case and an incremental
> > later patch could solve this problem in sysfs to turn shutdown on for
> > tpm1. As long as this logic is clearly documented it is probably an OK
> > step for now.
> 
> This I'm not actually sure about: it seems that there are other places
> than sysfs where chip->ops is referenced without being guarded by
> tpm_try_get_ops. If we rely on just NULLing out chip->ops this could
> be dangerous.  I'll look at sending a patch for this first.

If that is the case then we have an existing bug..

The only other user entry point is via the cdev, and those call
try_get_ops around all calls down into the tpm code.

Everything coming in via the kapi must call tpm_chip_find_get, which
does try_get_ops.

> > I think the original patch got a bit stuck on exactly how to do this,
> > but yes, somehow the common shutdown method is called. Either from the
> > driver core (preferred, IHMO) or via patching every single TPM driver.
> 
> I think the original thread was leaning towards (and I agree with)
> moving it into the core. Just to make sure I'm understanding the code
> structure correctly, tpm-chip.c is part of that core and a reasonable
> place for shared functionality, correct?

Yes..

But I went I said driver core, I ment by adding tpm_class->shutdown
that is called by drivers/base/... 'or something like that'

The trouble is how to consistently get the machine shutdown callback
from the driver core.

Jason

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