linux-kernel - Re: [PATCH v9 16/17] tpm: take TPM chip power gating out of tpm

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Message-ID: <20181119155530.GB13298@linux.intel.com>
Date:   Mon, 19 Nov 2018 17:55:30 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     "Winkler, Tomas" <tomas.winkler@...el.com>
Cc:     "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        "Struk, Tadeusz" <tadeusz.struk@...el.com>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        Nayna Jain <nayna@...ux.ibm.com>,
        Peter Huewe <peterhuewe@....de>,
        Jason Gunthorpe <jgg@...pe.ca>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 16/17] tpm: take TPM chip power gating out of
 tpm_transmit()

On Mon, Nov 19, 2018 at 01:17:56PM +0000, Winkler, Tomas wrote:
> > On Sun, Nov 18, 2018 at 10:52:46PM +0000, Winkler, Tomas wrote:
> > > This is still NACK from my side
> > 
> > Last time you spoke about tboot intervention but I don't see why as even
> > sending a single command is not atomic in the true sense of the word i.e. if
> > there was a problem that would already affect the existing code and would
> > essentially mean that tboot itself is broken.
> So I've consulted the issue, I wasn't not correct in the description.
> Tboot cannot acquire  the locality, unless the host driver relinquish
> it, so the issue is opposite, driver is expected to relinquish the
> locality for tboot to work correctly. This is current status, other
> behavior will need a different implementation on both sides. 

The locality is reliquished after the command sequence (load and save
TPM space + command in /dev/tpmX case).

Is this really such a big issue? The intention is not keep the locality
reserved by the driver.

/Jarkko