linux-kernel - Re: [PATCH v2] tpm: Add Upgrade/Reduced mode support for TPM2 modules

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Date:   Mon, 2 Aug 2021 11:35:28 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Borys Movchan <borysmn@...s.com>
Cc:     Borys Movchan <Borys.Movchan@...s.com>,
        Peter Huewe <peterhuewe@....de>,
        Jason Gunthorpe <jgg@...pe.ca>, kernel <kernel@...s.com>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] tpm: Add Upgrade/Reduced mode support for TPM2 modules

On Fri, Jul 30, 2021 at 04:24:01PM +0200, Borys Movchan wrote:
> On 7/28/21 11:58 PM, Jarkko Sakkinen wrote:
> > On Wed, Jul 28, 2021 at 12:57:30PM +0200, Borys Movchan wrote:
> > > If something went wrong during the TPM firmware upgrade,
> > > like power failure or the firmware image file get corrupted,
> > > the TPM might end up in Upgrade or Failure mode upon the
> > > next start. The state is persistent between the TPM power
> > > cycle/restart.
> > >
> > > According to TPM specification:
> > >  * If the TPM is in Upgrade mode, it will answer with
> > >    TPM2_RC_UPGRADE to all commands except Field Upgrade
> > >    related ones.
> > >  * If the TPM is in Failure mode, it will allow performing
> > >    TPM initialization but will not provide any crypto
> > >    operations. Will happily respond to Field Upgrade calls.
> > >
> > > The fix adds the possibility to detect an active state of
> > > the TPM and gives the user-space a chance to finish the
> > > firmware upgrade/recover the TPM.
> >
> > This is different than telling what the patch does. It's just
> > describing a goal, but does not describe how the driver is
> > changed, and reasons for doing that.
> >
> > For instance, you check 'limited_mode' flag in a few sites.
> > How can I know that those are exactly the locations where this
> > needs to be done?
> >
> 
> Seems like I got what you are looking for. Let me try to explain the
> reasoning
> and doubts regarding what I meant under my change.

Please try to nail this in the commit message instead, and I'll
then review that.

/Jarkko