Re: [PATCH v5 4/5] Initialize TPM and get durations and timeouts

["Stefan Berger" <stefanb-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

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Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> 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 moved the start of the work call before the tpm_chip_register, so that 
we *queue* the TPM_Startup before user space can send its first command.

> 
> The long term goal is to move the get_timeouts call into tpm_register.

That may become a problem then.

   Stefan

> 
> Jason
> 
> 
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