docs: clean-up the xenpvh documentation

I noticed the code blocks where not rendering properly so thought I'd
better fix things up. So:

  - Use better title for the machine type
  - Explain why Xen is a little different
  - Add a proper anchor to the tpm-device link
  - add newline so code block properly renders
  - add some indentation to make continuation clearer

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20231207130623.360473-1-alex.bennee@linaro.org>
This commit is contained in:
Alex Bennée 2023-12-07 13:06:23 +00:00 committed by Stefan Hajnoczi
parent 755ae3811f
commit 06ecb6ac19
2 changed files with 24 additions and 17 deletions

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@ -1,3 +1,5 @@
.. _tpm-device:
===============
QEMU TPM Device
===============

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XENPVH (``xenpvh``)
Xen Device Emulation Backend (``xenpvh``)
=========================================
This machine creates a IOREQ server to register/connect with Xen Hypervisor.
When TPM is enabled, this machine also creates a tpm-tis-device at a user input
tpm base address, adds a TPM emulator and connects to a swtpm application
running on host machine via chardev socket. This enables xenpvh to support TPM
functionalities for a guest domain.
This machine is a little unusual compared to others as QEMU just acts
as an IOREQ server to register/connect with Xen Hypervisor. Control of
the VMs themselves is left to the Xen tooling.
More information about TPM use and installing swtpm linux application can be
found at: docs/specs/tpm.rst.
When TPM is enabled, this machine also creates a tpm-tis-device at a
user input tpm base address, adds a TPM emulator and connects to a
swtpm application running on host machine via chardev socket. This
enables xenpvh to support TPM functionalities for a guest domain.
More information about TPM use and installing swtpm linux application
can be found in the :ref:`tpm-device` section.
Example for starting swtpm on host machine:
.. code-block:: console
mkdir /tmp/vtpm2
swtpm socket --tpmstate dir=/tmp/vtpm2 \
--ctrl type=unixio,path=/tmp/vtpm2/swtpm-sock &
--ctrl type=unixio,path=/tmp/vtpm2/swtpm-sock &
Sample QEMU xenpvh commands for running and connecting with Xen:
.. code-block:: console
qemu-system-aarch64 -xen-domid 1 \
-chardev socket,id=libxl-cmd,path=qmp-libxl-1,server=on,wait=off \
-mon chardev=libxl-cmd,mode=control \
-chardev socket,id=libxenstat-cmd,path=qmp-libxenstat-1,server=on,wait=off \
-mon chardev=libxenstat-cmd,mode=control \
-xen-attach -name guest0 -vnc none -display none -nographic \
-machine xenpvh -m 1301 \
-chardev socket,id=chrtpm,path=tmp/vtpm2/swtpm-sock \
-tpmdev emulator,id=tpm0,chardev=chrtpm -machine tpm-base-addr=0x0C000000
-chardev socket,id=libxl-cmd,path=qmp-libxl-1,server=on,wait=off \
-mon chardev=libxl-cmd,mode=control \
-chardev socket,id=libxenstat-cmd,path=qmp-libxenstat-1,server=on,wait=off \
-mon chardev=libxenstat-cmd,mode=control \
-xen-attach -name guest0 -vnc none -display none -nographic \
-machine xenpvh -m 1301 \
-chardev socket,id=chrtpm,path=tmp/vtpm2/swtpm-sock \
-tpmdev emulator,id=tpm0,chardev=chrtpm -machine tpm-base-addr=0x0C000000
In above QEMU command, last two lines are for connecting xenpvh QEMU to swtpm
via chardev socket.