[Qemu-devel] [QAPI+QGA 3/3] QEMU Guest Agent (virtagent) v5

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

This is Set 3/3 of the QAPI+QGA patchsets.

These patches apply on top of qapi-backport-set2-v3, and can also be obtained from:
git://repo.or.cz/qemu/mdroth.git qapi-backport-set3-v5

(Set1+2 are a backport of some of the QAPI-related work from Anthony's
glib tree. The main goal is to get the basic code generation infrastructure in
place so that it can be used by the guest agent to implement a QMP-like guest
interface, and so that future work regarding the QMP conversion to QAPI can be
decoupled from the infrastructure bits. Set3 is the Qemu Guest Agent
(virtagent), rebased on the new code QAPI code generation infrastructure. This
is the first user of QAPI, QMP will follow.)
___

CHANGES SINCE V4:
 - Removed timeout mechanism via worker thread/pthread_cancel due to potential memory leak. Will re-introduce guest-side timeout support in future version.
 - Fixed up fsfreeze code to use enums specified within the guest agent's qapi schema.
 - Fixed memory leak due to a log statement, and added missing cleanup functions for heap-allocated g_error objects.
 - Made "mode" param to guest-file-open optional, defaults to "r" (read-only)

CHANGES SINCE V3:
 - Fixed error-handling issues in fsfreeze commands leading to certain mounted directories causing freeze/thaw operations to fail
 - Added cleanup hook to thaw filesystems on graceful guest agent exit
 - Removed unused enum values and added additional details to schema documentation
 - Fixed build issue that was missed due to deprecated files in source tree, removed unused includes

CHANGES SINCE V2:
 - Rebased on new QAPI code generation framework
 - Dropped ability for QMP to act as a proxy for the guest agent, will be added when new QMP server is backported from Anthony's glib tree
 - Replaced negotiation/control events with a simple 2-way handshake implemented by a standard RPC (guest-sync)
 - Removed enforcement of "pristine" sessions, state is now global/persistant across multiple clients/connections
 - Fixed segfault in logging code
 - Added Jes' filesystem freeze patches 
 - General cleanups

CHANGES SINCE V1:
 - Added guest agent worker thread to execute RPCs in the guest. With this in place we have a reliable timeout mechanism for hung commands, currently set at 30 seconds.
 - Add framework for registering init/cleanup routines for stateful RPCs to clean up after themselves after a timeout.
 - Added the following RPCs: guest-file-{open,close,read,write,seek}, guest-shutdown, guest-info, and removed stubs for guest-view-file (now deprecated)
 - Added GUEST_AGENT_UP/GUEST_AGENT_DOWN QMP events
 - Switched to a TCP-style host-initiated 3-way handshake for channel negotiation, this simplifies client negotiation/interaction over the wire
 - Added configurable log level/log file/pid file options for guest agent
 - Various fixes for bugs/memory leaks and checkpatch.pl fixups

ISSUES/TODOS:
 - Add unit tests for guest agent wire protocol

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/qga.sock,server,nowait,id=qga \
  -device virtio-serial \
  -device virtserialport,chardev=qga,name=qga"

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

communicate with the guest agent:
  mdroth@illuin:~$ sudo socat unix-connect:/tmp/qga.sock readline
  {"execute":"guest-sync", "arguments":{"id":1234}}
  {"return": 1234}

  {"execute":"guest-info"}
  {"return": {}}

  {"execute": "guest-info"}
  {"return": {"version": "1.0"}}

  {"execute":"guest-file-open", "arguments":{"filepath":"/tmp/testqga","mode":"w+"}}
  {"return": 0}
  {"execute":"guest-file-write", "arguments":{"filehandle":0,"data_b64":"aGVsbG8gd29ybGQhCg==","count":13}} // writes "hello world!\n"
  {"return": {"count": 13, "eof": false}}

  {"execute":"guest-file-open", "arguments":{"filepath":"/tmp/testqga","mode":"r"}}
  {"return": 1}
  {"execute":"guest-file-read", "arguments":{"filehandle":1,"count":1024}}
  {"return": {"buf": "aGVsbG8gd29ybGQhCg==", "count": 13, "eof": true}}
  {"execute":"guest-file-close","arguments":{"filehandle":1}}
  {"return": {}}

 Makefile                        |   22 +-
 configure                       |    1 +
 qapi-schema-guest.json          |  202 +++++++++++++
 qemu-ga.c                       |  631 +++++++++++++++++++++++++++++++++++++++
 qerror.c                        |    4 +
 qerror.h                        |    3 +
 qga/guest-agent-command-state.c |   73 +++++
 qga/guest-agent-commands.c      |  522 ++++++++++++++++++++++++++++++++
 qga/guest-agent-core.h          |   30 ++
 9 files changed, 1483 insertions(+), 5 deletions(-)