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

[Zhi Yong Wu <zwu.kernel@gmail.com>]

HI, Michael,

On Tue, Jul 5, 2011 at 9:21 PM, Michael Roth <mdroth@linux.vnet.ibm.com> wrote:
> 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 from:
> 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.)
> ___
>
> CHANGES SINCE V5:
>  - 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.
>
> 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
Is the above command "./qemu-ga" issued on guest teminal or hypervisor teminal?

>
> start/use qmp:
>  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(-)
>
>
>
-- 
Regards,

Zhi Yong Wu