[Qemu-devel] [RFC][PATCH v1 00/11] QEMU Guest Agent: QMP-based host/guest communication (virtagent)

[Michael Roth <mdroth@linux.vnet.ibm.com>]

These apply on top of Anthony's glib tree, commit 03d5927deb5e6baebaade1b4c8ff2428a85e125c currently, and can also be obtained from:
git://repo.or.cz/qemu/mdroth.git qga_v1

The QGA-specific patches are in pretty rough shape, and there are some outstanding issues that I'll note below. I just wanted to put the general approach out there for consideration. Patch-level comments/review are still much-appreciated though.

However, patches 1-5 are general json/QAPI-related fixes. Anthony, please consider pulling these into your glib tree. The json fix-ups may need further evaluation, but I'm confident they're at least an improvement. The QAPI ones are trivial fix-ups.

ISSUES/TODOS:

 - QMP's async callbacks expect the command results to be de-marshalled beforehand. This is completely infeasible to attempt outside of the code generator, so this is a big area that needs to be addressed. So for now, only the 'guest-ping' command works, since it has no return value. The dummy "guest-view-file" command will cause an error to be reported to the client.
 - qemu-ga guest daemon is currently not working over virtio-serial or isa-serial. This is probably an issue with how I'm using glib's io channel interfaces, still investigating. This means the only way to currently test is by invocing qemu-ga with "-c unix-listen -p <sockpath>", then doing something like `socat /dev/ttyS0,raw,echo=0 unix-connect:<sockpath>`.
 - guest-view-file is a stub, and will be broken out into an open/read/close set of RPCs, possibly with a high-level interface built around those.

OVERVIEW

For a better overview of what these patches are meant to accomplish, please reference the RFC for virtagent:

http://comments.gmane.org/gmane.comp.emulators.qemu/96096

These patches integrate the previous virtagent guest agent work directly in QAPI/QMP to leverage it's auto-generated marshalling code. This has numerous benefits:

 - addresses previous concerns over relying on external libraries to handle data encapsulation
 - reduces the need for manual unmarshalling of requests/responses, which makes adding new RPCs much safer/less error-prone, as well as cutting down on redundant code
 - QAPI documentation aligns completely with guest-side RPC implementation
 - is Just Better (TM)

BUILD/USAGE

build:
  ./configure --target-list=x86_64-softmmu
  make
  make qemu-ga #should be built on|for target guest

start guest:
  qemu \
  -drive file=/home/mdroth/vm/rhel6_64_base.raw,snapshot=off,if=virtio \
  -net nic,model=virtio,macaddr=52:54:00:12:34:00 \
  -net tap,script=/etc/qemu-ifup \
  -vnc :1 -m 1024 --enable-kvm \
  -chardev socket,path=/tmp/mon-qmp.sock,server,nowait,id=mon-qmp \
  -qmp mon-qmp \
  -chardev qmp_proxy,path=/tmp/qmp-proxy2.sock,server,nowait,id=qmp_proxy \ 
  -device virtio-serial \
  -device virtserialport,chardev=qmp_proxy,name=qcg"

use guest agent:
  ./qemu-ga -h
  ./qemu-ga -c virtio-serial -p /dev/virtio-ports/qcg

start/use qmp:
  mdroth@illuin:~$ sudo socat unix-connect:/tmp/mon-qmp.sock readline
  {"QMP": {"version": {"qemu": {"micro": 50, "minor": 13, "major": 0}, "package": ""}, "capabilities": []}}
  {"execute":"guest-ping"}
  {"return": {}}

__

 Makefile               |    5 +-
 Makefile.objs          |    1 +
 configure              |    6 +-
 guest-agent-commands.c |   24 +++
 guest-agent-core.c     |  143 +++++++++++++
 guest-agent-core.h     |   21 ++
 json-lexer.c           |   22 ++-
 json-lexer.h           |    1 +
 json-parser.c          |    6 +-
 json-streamer.c        |   35 ++-
 qemu-char.c            |   46 +++++
 qemu-ga.c              |  522 ++++++++++++++++++++++++++++++++++++++++++++++++
 qmp-core.c             |   13 +-
 qmp-core.h             |    7 +-
 qmp-gen.py             |    2 +-
 qmp-proxy-core.h       |   20 ++
 qmp-proxy.c            |  335 +++++++++++++++++++++++++++++++
 vl.c                   |    1 +
 18 files changed, 1181 insertions(+), 29 deletions(-)