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Re: [PATCH 2/2] tpm: add backend for mssim


From: Stefan Berger
Subject: Re: [PATCH 2/2] tpm: add backend for mssim
Date: Thu, 15 Dec 2022 13:46:54 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.1



On 12/15/22 13:01, James Bottomley wrote:
From: James Bottomley <James.Bottomley@HansenPartnership.com>

The Microsoft Simulator (mssim) is the reference emulation platform
for the TCG TPM 2.0 specification.

https://github.com/Microsoft/ms-tpm-20-ref.git

It exports a fairly simple network socket baset protocol on two
sockets, one for command (default 2321) and one for control (default
2322).  This patch adds a simple backend that can speak the mssim
protocol over the network.  It also allows the host, and two ports to
be specified on the qemu command line.  The benefits are twofold:
firstly it gives us a backend that actually speaks a standard TPM
emulation protocol instead of the linux specific TPM driver format of
the current emulated TPM backend and secondly, using the microsoft
protocol, the end point of the emulator can be anywhere on the
network, facilitating the cloud use case where a central TPM service
can be used over a control network.

The implementation does basic control commands like power off/on, but
doesn't implement cancellation or startup.  The former because
cancellation is pretty much useless on a fast operating TPM emulator
and the latter because this emulator is designed to be used with OVMF
which itself does TPM startup and I wanted to validate that.

To run this, simply download an emulator based on the MS specification
(package ibmswtpm2 on openSUSE) and run it, then add these two lines
to the qemu command and it will use the emulator.

     -tpmdev mssim,id=tpm0 \
     -device tpm-crb,tpmdev=tpm0 \

to use a remote emulator replace the first line with

     -tpmdev 
"{'type':'mssim','id':'tpm0','command':{'type':inet,'host':'remote','port':'2321'}}"

tpm-tis also works as the backend.

Since this device does not properly support migration you have to register a 
migration blocker.

   Stefan



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