linux-kernel - Re: [PATCH 2/2] tpm: tpm_crb: enhance resource mapping mechanism for supporting AMD's fTPM

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Date:   Fri, 30 Aug 2019 22:54:59 +0900
From:   Seunghun Han <kkamagui@...il.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.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 2/2] tpm: tpm_crb: enhance resource mapping mechanism for
 supporting AMD's fTPM

>
> On Fri, Aug 30, 2019 at 06:56:39PM +0900, Seunghun Han wrote:
> > I got an AMD system which had a Ryzen Threadripper 1950X and MSI
> > mainboard, and I had a problem with AMD's fTPM. My machine showed an error
> > message below, and the fTPM didn't work because of it.
> >
> > [  5.732084] tpm_crb MSFT0101:00: can't request region for resource
> >              [mem 0x79b4f000-0x79b4ffff]
> > [  5.732089] tpm_crb: probe of MSFT0101:00 failed with error -16
> >
> > When I saw the iomem, I found two fTPM regions were in the ACPI NVS area.
> > The regions are below.
> >
> > 79a39000-79b6afff : ACPI Non-volatile Storage
> >   79b4b000-79b4bfff : MSFT0101:00
> >   79b4f000-79b4ffff : MSFT0101:00
> >
> > After analyzing this issue, I found that crb_map_io() function called
> > devm_ioremap_resource() and it failed. The ACPI NVS didn't allow the TPM
> > CRB driver to assign a resource in it because a busy bit was set to
> > the ACPI NVS area.
> >
> > To support AMD's fTPM, I added a function to check intersects between
> > the TPM region and ACPI NVS before it mapped the region. If some
> > intersects are detected, the function just calls devm_ioremap() for
> > a workaround. If there is no intersect, it calls devm_ioremap_resource().
> >
> > Signed-off-by: Seunghun Han <kkamagui@...il.com>
> > ---
> >  drivers/char/tpm/tpm_crb.c | 25 +++++++++++++++++++++++--
> >  1 file changed, 23 insertions(+), 2 deletions(-)
>
> This still seems to result in two drivers controlling the same
> memory. Does this create bugs and races during resume?
>
> Jason

When I tested this patch in my machine, it seemed that ACPI NVS was
saved after TPM CRB driver sent "TPM2_Shutdown(STATE)" to the fTPM
while suspending. Then, ACPI NVS was restored while resuming.
After resuming, PCRs didn't change and TPM2 tools such as
tpm2_pcrlist, tpm2_extend, tpm2_getrandoms worked well.
So, according to my test result, it seems that the patch doesn't
create bugs and race during resume.

Seunghun