linux-kernel - Re: [PATCH] x86: tpm: Remove a busy bit of the NVS area for supporting AMD's fTPM

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Message-ID: <20190829153437.gjcqfolsc26vyt4x@linux.intel.com>
Date:   Thu, 29 Aug 2019 18:34:37 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Seunghun Han <kkamagui@...il.com>
Cc:     Matthew Garrett <mjg59@...f.ucam.org>,
        Matthew Garrett <mjg59@...gle.com>,
        Peter Huewe <peterhuewe@....de>,
        "open list:TPM DEVICE DRIVER" <linux-integrity@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: tpm: Remove a busy bit of the NVS area for
 supporting AMD's fTPM

On Wed, Aug 28, 2019 at 06:36:04PM +0900, Seunghun Han wrote:
> >
> > On Wed, Aug 28, 2019 at 01:36:30AM +0900, Seunghun Han wrote:
> >
> > > I got your point. Is there any problem if some regions which don't
> > > need to be handled in NVS area are saved and restored? If there is a
> > > problem, how about adding code for ignoring the regions in NVS area to
> > > the nvs.c file like Jarkko said? If we add the code, we can save and
> > > restore NVS area without driver's interaction.
> >
> > The only thing that knows which regions should be skipped by the NVS
> > driver is the hardware specific driver, so the TPM driver needs to ask
> > the NVS driver to ignore that region and grant control to the TPM
> > driver.
> >
> > --
> > Matthew Garrett | mjg59@...f.ucam.org
> 
> Thank you, Matthew and Jarkko.
> It seems that the TPM driver needs to handle the specific case that
> TPM regions are in the NVS. I would make a patch that removes TPM
> regions from the ACPI NVS by requesting to the NVS driver soon.
> 
> Jarkko,
> I would like to get some advice on it. What do you think about
> removing TPM regions from the ACPI NVS in TPM CRB driver? If you don't
> mind, I would make the patch about it.

I'm not sure if ignoring is right call. Then the hibernation behaviour
for TPM regions would break.

Thus, should be "ask access" rather than "grant control".

/Jarkko