Re: [PATCH v8 2/2] tpm: add backend for mssim

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

Hi James,

On 4/10/23 20:42, 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 based 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 two sockets to be
> specified on the 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.
> 
> Signed-off-by: James Bottomley <jejb@linux.ibm.com>
> Acked-by: Markus Armbruster <armbru@redhat.com>
> 
> ---
> 
> v2: convert to SocketAddr json and use qio_channel_socket_connect_sync()
> v3: gate control power off by migration state keep control socket disconnected
>      to test outside influence and add docs.
> v7: TPMmssim -> TPMMssim; doc and json fixes
>      Make command socket open each time (makes OS debugging easier)
> ---
>   MAINTAINERS              |   6 +
>   backends/tpm/Kconfig     |   5 +
>   backends/tpm/meson.build |   1 +
>   backends/tpm/tpm_mssim.c | 319 +++++++++++++++++++++++++++++++++++++++
>   backends/tpm/tpm_mssim.h |  44 ++++++
>   docs/specs/tpm.rst       |  39 +++++
>   qapi/tpm.json            |  32 +++-
>   softmmu/tpm-hmp-cmds.c   |   9 ++
>   8 files changed, 451 insertions(+), 4 deletions(-)
>   create mode 100644 backends/tpm/tpm_mssim.c
>   create mode 100644 backends/tpm/tpm_mssim.h


> diff --git a/docs/specs/tpm.rst b/docs/specs/tpm.rst
> index efe124a148..4fe6c5f051 100644
> --- a/docs/specs/tpm.rst
> +++ b/docs/specs/tpm.rst
> @@ -274,6 +274,42 @@ available as a module (assuming a TPM 2 is passed through):
>     /sys/devices/LNXSYSTEM:00/LNXSYBUS:00/MSFT0101:00/tpm/tpm0/pcr-sha256/9
>     ...
>   
> +The QEMU TPM Microsoft Simulator Device
> +---------------------------------------
> +
> +The Microsoft Simulator (mssim) is the reference emulation platform
> +for the TCG TPM 2.0 specification.  It provides a reference
> +implementation for the TPM 2.0 written by Microsoft (See
> +`ms-tpm-20-ref`_ on github).  The reference implementation starts a
> +network server and listens for TPM commands on port 2321 and TPM
> +Platform control commands on port 2322, although these can be altered.
> +The QEMU mssim TPM backend talks to this implementation.  By default
> +it connects to the default ports on localhost:
> +
> +.. code-block:: console
> +
> +  qemu-system-x86_64 <qemu-options> \
> +    -tpmdev mssim,id=tpm0 \
> +    -device tpm-crb,tpmdev=tpm0
> +
> +
> +Although it can also communicate with a remote host, which must be
> +specified as a SocketAddress via json or dotted keys on the command
> +line for each of the command and control ports:
> +
> +.. code-block:: console
> +
> +  qemu-system-x86_64 <qemu-options> \
> +    -tpmdev "{'type':'mssim','id':'tpm0','command':{'type':'inet','host':'remote','port':'2321'},'control':{'type':'inet','host':'remote','port':'2322'}}" \
> +    -device tpm-crb,tpmdev=tpm0

Did you test running this command line on a big-endian host?

> +The mssim backend supports snapshotting and migration by not resetting
> +the TPM on start up and not powering it down on halt if the VM is in
> +migration, but the state of the Microsoft Simulator server must be
> +preserved (or the server kept running) outside of QEMU for restore to
> +be successful.
> +
>   The QEMU TPM emulator device
>   ----------------------------
>   
> @@ -547,3 +583,6 @@ the following:
>   
>   .. _SWTPM protocol:
>      https://github.com/stefanberger/swtpm/blob/master/man/man3/swtpm_ioctls.pod
> +
> +.. _ms-tpm-20-ref:
> +   https://github.com/microsoft/ms-tpm-20-ref