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 09:43:34 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Seunghun Han <kkamagui@...il.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Peter Huewe <peterhuewe@....de>,
        "open list:TPM DEVICE DRIVER" <linux-integrity@...r.kernel.org>,
        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