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

[James Bottomley <jejb@linux.ibm.com>]

On Thu, 2022-12-15 at 13:46 -0500, Stefan Berger wrote:
> 
> 
> 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.

Actually it seems to support migration just fine.  Currently the PCR's
get zero'd which is my fault for doing a TPM power off/on, but
switching that based on state should be an easy fix.

James