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From: Stefan Berger <stefanb@linux.vnet.ibm.com>
Date: Wed, 1 Mar 2017 07:25:28 -0500
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Subject: Re: [Qemu-devel] [PATCH v5 1/4] Provide support for the CUSE TPM
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To: "Daniel P. Berrange" <berrange@redhat.com>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Stefan Berger <stefanb@us.ibm.com>, "mst@redhat.com" <mst@redhat.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, "SERBAN, CRISTINA" <cs1731@att.com>, "Xu, Quan" <quan.xu@intel.com>, "silviu.vlasceanu@gmail.com" <silviu.vlasceanu@gmail.com>, "hagen.lauer@huawei.com" <hagen.lauer@huawei.com>, "SHIH, CHING C" <cs1815@att.com>

On 06/16/2016 04:25 AM, Daniel P. Berrange wrote:
> On Thu, Jun 16, 2016 at 09:05:20AM +0100, Dr. David Alan Gilbert wrote:
>> * Stefan Berger (stefanb@linux.vnet.ibm.com) wrote:
>>> On 06/15/2016 03:30 PM, Dr. David Alan Gilbert wrote:
>> <snip>
>>
>>>> So what was the multi-instance vTPM proxy driver patch set about?
>>> That's for containers.
>> Why have the two mechanisms? Can you explain how the multi-instance
>> proxy works; my brief reading when I saw your patch series seemed
>> to suggest it could be used instead of CUSE for the non-container case.
> One of the key things that was/is not appealing about this CUSE approach
> is that it basically invents a new ioctl() mechanism for talking to
> a TPM chardev. With in-kernel vTPM support, QEMU probably doesn't need
> to have any changes at all - its existing driver for talking to TPM

We still need the control channel with the vTPM to reset it upon VM 
reset, for getting and setting the state of the vTPM upon 
snapshot/suspend/resume, changing locality, etc.

    Stefan