This set of patches is meant to be applied on top of the Virtproxy v1 patchset.
OVERVIEW: There are a wide range of use cases motivating the need for a guest agent of some sort to extend the functionality/usability/control offered by QEMU. Some examples include graceful guest shutdown/reboot and notifications thereof, copy/paste syncing between host/guest, guest statistics gathering, file access, etc. Ideally these would all be served by a single, easilly extensible agent that can be deployed in a wide range of guests. Virtagent is an XMLRPC server integrated into the Virtproxy guest daemon and aimed at providing this type of functionality. This code is very rough, and I'll to document most of the bugs/shortcomings we're aware of in this version of the patchset. The main goal of this RFC to get feedback on the types of core functionality we would need in an agent of this sort, as well as feedback on the general approach/architecture implemented here. Any feedback is greatly appreciated however. To start off this discussion, there have been some recent posts about how much an agent of this sort overlaps with the goals of the Matahari project (https://fedorahosted.org/matahari/). While both of these approaches are at least *feasible*, our use cases require the ability to deploy to guests which may not support virtio-serial, which currently rules Matahari out. This support could be added however: the virtproxy layer used by this agent actually lends itself to extending such support to other agents/services, or a more direct approach could be taken in adding support for isa-serial. The question that remains however is one of scope. This agent is intended purely as a means to extend qemu's abilities to perform hypervisor-specific work, whereas Matahari aims to extend general system management capabilities to guests (please correct me if I'm oversimplifying). Virtagent cannot meet Matahari's goals, whereas Matahari technically can meet Virtagent's. My contention however is that the qemu-specific scope/API and shared code base with a more closely integrated agent will provide a more expedient route to functional improvements to qemu, while still allowing for the additional functionality/management capabilities provided by something like Matahari. DESIGN: There are actually 2 RPC servers: 1) a server in the guest integrated into the Virtproxy guest daemon which handles RPC requests from QEMU 2) a server in the host (integrated into the Virtproxy host daemon, which we plan to integrate directly into qemu) to handle RPC requests sent by the guest agent (mainly for handling asynchronous events reported by the agent). At the Virtagent level, communication is done via standard RPCs (HTTP/TCP between host and guest). Virtproxy transparently handles transport over a network or isa/virtio serial channel, allowing the agent to be deployed on older guests which may not support virtio-serial. Currently there are only 2 RPCs implemented for the guest server (getfile and getdmesg), and 0 for the host. Additional RPCs can be added fairly easily, but are dependent on feedback from here and elsewhere. ping/status, shutdown, and reboot are likely candidates (although the latter 2 will likely require asynchronous notifications to the host RPC server to implement reliably). EXAMPLE USAGE: The commandline options are a little convoluted right now; this will addressed in later revisions. - Configure guest agent to talk to host via virtio-serial # start guest with virtio-serial. for example (RHEL6s13): qemu \ -device virtio-serial \ -chardev socket,path=/tmp/test0-virtioconsole.sock,server,nowait,id=test0 \ -device virtconsole,chardev=test0,name=test0 \ -chardev socket,path=/tmp/test1-virtio-serial.sock,server,nowait,id=test1 \ -device virtserialport,chardev=test1,name=test1 \ -chardev socket,path=/tmp/test2-virtio-serial.sock,server,nowait,id=test2 \ -device virtserialport,chardev=test2,name=test2 \ -monitor stdio ... # in the host: ./qemu-vp -c unix-connect:/tmp/test2-virtio-serial.sock:- \ -o virtagent:/tmp/virtagent-guest-client.sock:- # in the guest: ./qemu-vp -c virtserial-open:/dev/virtio-ports/test2:- -g ... # monitor commands (qemu) agent_viewdmesg [139311.710326] wlan0: deauthenticating from 00:30:bd:f7:12:d5 by local choice (reason=3) [139323.469857] wlan0: deauthenticating from 00:21:29:cd:41:ee by local choice (reason=3) ... [257683.375646] wlan0: authenticated [257683.375684] wlan0: associate with AP 00:30:bd:f7:12:d5 (try 1) [257683.377932] wlan0: RX AssocResp from 00:30:bd:f7:12:d5 (capab=0x411 status=0 aid=4) [257683.377940] wlan0: associated (qemu) agent_viewfile /proc/meminfo MemTotal: 3985488 kB MemFree: 400524 kB Buffers: 220556 kB Cached: 2073160 kB SwapCached: 0 kB ... Hugepagesize: 2048 kB DirectMap4k: 8896 kB DirectMap2M: 4110336 kB KNOWN ISSUES/PLANS: - the client socket that qemu connects to send RPCs is a hardcoded filepath. This is unacceptable as the socket is channel/process specific and things will break when multiple guests are started. - capability negotiation will be needed to handle version/architecture differences. - proper channel negotiation is critical to avoiding hung monitors and such when a guest reboots or the guest agent is stopped for whatever reason. additionally, a timeout may need to be imposed on the amount of time the http read handler can block the monitor. - additional host-to-guest RPCs as well as asynchronous notifications via guest-to-host RPCs for events such as shutdown/reboot/agent up/agent down - switch all RPC communication over to non-blocking/asynchronous read/write callbacks to avoid deadlocks. Makefile | 2 +- Makefile.target | 2 +- configure | 25 ++++ hmp-commands.hx | 32 +++++ monitor.c | 1 + qemu-vp.c | 119 +++++++++++++++-- qerror.c | 4 + qerror.h | 3 + qmp-commands.hx | 68 +++++++++ virtagent-common.c | 381 +++++++++++++++++++++++++++++++++++++++++++++++++++ virtagent-common.h | 63 +++++++++ virtagent-daemon.c | 216 +++++++++++++++++++++++++++++ virtagent-daemon.h | 21 +++ virtagent.c | 298 ++++++++++++++++++++++++++++++++++++++++ virtagent.h | 32 +++++ virtproxy-builtin.c | 30 ++++ 16 files changed, 1286 insertions(+), 11 deletions(-)
