On Tue, Feb 09, 2016 at 09:52:28AM -0700, Jason Gunthorpe wrote:
> On Tue, Feb 09, 2016 at 11:19:15AM -0500, Stefan Berger wrote:
> > Jason Gunthorpe <[email protected]> wrote on 02/09/2016 
> > 12:33:23
> > AM:
> > 
> > 
> > >
> > > On Mon, Feb 08, 2016 at 02:27:07PM -0500, Stefan Berger wrote:
> > > > Add the retrieval of TPM 1.2 durations and timeouts. Since this requires
> > > > the startup of the TPM, do this for TPM 1.2 and TPM 2.
> > > >
> > > > To not allow to interleave with commands from user space, so send the
> > > > TPM_Startup as the first command. The timeouts can then be gotten at any
> > > > later time, even interleaved with commands from user space.
> > >
> > > Do not call tpm_register until get_timeouts has completed and this
> > > will naturally be avoided the same way every other TPM driver does.
> > 
> > Getting the timeouts cannot complete before the TPM emulator has started, 
> > which
> > in turn cannot start before the ioctl returns. We don't know whether user 
> > space
> > starts a client first on /dev/tpm1 or the TPM emulator starts first on the 
> > file
> > descriptor. We can control which command gets *queued* for the TPM emulator 
> > and
> > that's what I am doing by having the kernel queue the startup command first.
> 
> I keep saying this same solution - start a work queue just before the
> ioctl returns and do the get_timeouts and registration in there.

*Maybe* it would be worth to check David's patch:

https://github.com/PeterHuewe/linux-tpmdd/commit/9329f13c403daf1f4bd1e715d2ba0866e089fb1d

/Jarkko

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