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[Qemu-devel] [QAPI+QGA 3/3] QEMU Guest Agent (virtagent) v6

From: Michael Roth
Subject: [Qemu-devel] [QAPI+QGA 3/3] QEMU Guest Agent (virtagent) v6
Date: Tue, 5 Jul 2011 08:21:36 -0500

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

These patches apply on top of qapi-backport-set2-v5, and can also be obtained 
git://repo.or.cz/qemu/mdroth.git qapi-backport-set3-v6

(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.)

 - switched to using qemu malloc/list functions where possible
 - removed unused proxy_path field in struct GAState
 - pid file now opened write-only, removed lockf() in favor of O_EXCL, added 
SIGINT/SIGTERM signal handlers to handle cleanup
 - cleaned up error-handling, switched to asserts where appropriate, removed 
unecessary gotos and NULL checks for qemu_free()/qobject_decref()
 - refactored send_payload() using helper functions
 - fixed improper handling of pidfile fd==0
 - changed guest-shutdown's "shutdown_mode" param to "mode"
 - switched to using kernel-generated FDs for guest-file-open rather than an 
autoincrement value
 - add maximum chunk size of guest-file-read/guest-file-write
 - added checks to avoid guest-file-write from writing data beyond the provided 
data buffer
 - made logging best-effort, removed handling of failures to log as errors
 - guest-shutdown exec errors now logged to guest syslog, clarified shutdown's 
asynchronous, no gauruntee nature in schema.

 - 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 
 - 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)

 - 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 
 - Fixed build issue that was missed due to deprecated files in source tree, 
removed unused includes

 - 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

 - 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 
 - 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

 - Add unit tests for guest agent wire protocol


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


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

 - 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)


  ./configure --target-list=x86_64-softmmu
  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

start/use qmp:
  address@hidden:~$ sudo socat unix-connect:/tmp/qga.sock readline
  {"execute":"guest-sync", "arguments":{"id":1234}}
  {"return": 1234}

  {"return": {}}

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

  {"return": 0}
"arguments":{"filehandle":0,"data_b64":"aGVsbG8gd29ybGQhCg==","count":13}} // 
writes "hello world!\n"
  {"return": {"count": 13, "eof": false}}

  {"return": 1}
  {"execute":"guest-file-read", "arguments":{"filehandle":1,"count":1024}}
  {"return": {"buf": "aGVsbG8gd29ybGQhCg==", "count": 13, "eof": true}}
  {"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(-)

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