linux-kernel - Re: [PATCH 11/12] habanalabs/gaudi2: add tpm attestation info uapi

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Date:   Tue, 28 Jun 2022 11:12:03 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Oded Gabbay <ogabbay@...nel.org>
Cc:     "Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
        Dani Liberman <dliberman@...ana.ai>
Subject: Re: [PATCH 11/12] habanalabs/gaudi2: add tpm attestation info uapi

On Tue, Jun 28, 2022 at 11:51:48AM +0300, Oded Gabbay wrote:
> On Tue, Jun 28, 2022 at 9:36 AM Greg KH <gregkh@...uxfoundation.org> wrote:
> >
> > On Mon, Jun 27, 2022 at 11:26:19PM +0300, Oded Gabbay wrote:
> > > From: Dani Liberman <dliberman@...ana.ai>
> > >
> > > User will provide a nonce via the ioctl, and will retrieve
> > > attestation data of the boot from the tpm, generated using given
> > > nonce.
> >
> > Why not use the normal TPM api instead of a new/custom one?  Or is this
> > not a "normal" TPM device?  If not, you should say what it really is.
> >
> > thanks,
> >
> > greg k-h
> 
> Honestly, I'm not that knowledgeable about it. It is hidden behind our
> firmware code. We just provide a communication method between the
> userspace and the firmware, as the userspace can't interact directly
> with the f/w. i.e. The driver is a transparent tunnel, it doesn't
> interact with registers of the TPM device itself. The "real" driver is
> in our firmware.
> 
> So basically we just got definitions from the f/w how to fetch the
> data from them and how to expose it to the user and that's it.
> 
> What to do in this case ? Is this considered a "real" TPM ? I imagine
> I won't be able to connect to a standard tpm driver in the kernel as
> the h/w is not exposed to me.

How is this hardware designed?  Is the TPM in here supposed to be a
real TPM for userspace to use?  Or is this just a random hardware thing
that you use to validate your device somehow and is not supposed to be a
normal TPM as per the specification?

thanks,

greg k-h