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

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Date:   Wed, 4 Sep 2019 03:14:48 +0900
From:   Seunghun Han <kkamagui@...il.com>
To:     "Safford, David (GE Global Research, US)" <david.safford@...com>
Cc:     Jason Gunthorpe <jgg@...pe.ca>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Peter Huewe <peterhuewe@....de>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        Matthew Garrett <mjg59@...gle.com>,
        "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

> I tried your patch out on my systems with a "reserved" but not "NVS"
> region conflict, and you are correct - the region is not busy, and
> the driver is able to map the buffers with your patch.
>
> > First of all, I misunderstood your message.
> > I have to tell you about the buffer size exactly. The command and response
> > buffer sizes in ACPI table were 0x1000 and this was 4K, not 1K. The sizes in
> > the control register were 0x4000 and this was 16K (large buffer size), not 4K.
> > I have been using the TPM for my research and the typical cases like creating
> > public/private keys, encrypting/decrypting data, sealing/unsealing a secrete,
> > and getting random numbers are not over 4K buffer. So, as you know, I think
> > the 4K buffer can handle the most cases and the current implementation of
> > crb_fixup_cmd_size() works well. If you concern the specific case that uses
> > over 4K buffer, please let me know.
>
> I have read postings of some systems where ACPI says 1K, but in all of my cases
> that I can test,  you are correct that ACPI is saying 4K instead of the device's 16K.
> I tried really hard, but couldn't send any valid requests over 4K, (I believe that's
> actually the max by the spec), and therefore never saw any failures on my
> systems. I think the driver behavior is wrong for those other cases, but perhaps
> this should wait until someone can get access and do the testing.
>
> So I'm happy with your patches, other than what is decided for the nvs driver
> conflict. I'm testing them on some production systems, and have seen no other
> issues.
>
> dave

Thank you for your help and testing. I would like to make patch v2 to
change the point that kbuild robot told me.
If you don't mind, may I add "tested-by" tag to patch v2 with your
name and email address?

Seunghun