[PATCH 3/3] qemu: EVENTHANDLERS.txt: Move to kbase and rSTisze

Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- docs/kbase/index.rst | 3 ++ docs/kbase/internals/meson.build | 1 + .../kbase/internals/qemu-event-handlers.rst | 44 ++++++++++--------- 3 files changed, 28 insertions(+), 20 deletions(-) rename src/qemu/EVENTHANDLERS.txt => docs/kbase/internals/qemu-event-handlers.rst (64%) diff --git a/docs/kbase/index.rst b/docs/kbase/index.rst index d0f2167be8..8b710db85a 100644 --- a/docs/kbase/index.rst +++ b/docs/kbase/index.rst @@ -107,3 +107,6 @@ Internals `QEMU migration internals <internals/qemu-migration.html>`__ Description of migration phases in the ``v2`` and ``v3`` migration protocol. + +`QEMU monitor event handling <internals/qemu-event-handlers.html>`__ + Brief outline how events emitted by qemu on the monitor are handlded. diff --git a/docs/kbase/internals/meson.build b/docs/kbase/internals/meson.build index 4f7b223786..a16d5a290b 100644 --- a/docs/kbase/internals/meson.build +++ b/docs/kbase/internals/meson.build @@ -5,6 +5,7 @@ docs_kbase_internals_files = [ 'locking', 'migration', 'overview', + 'qemu-event-handlers', 'qemu-migration', 'qemu-threads', 'rpc', diff --git a/src/qemu/EVENTHANDLERS.txt b/docs/kbase/internals/qemu-event-handlers.rst similarity index 64% rename from src/qemu/EVENTHANDLERS.txt rename to docs/kbase/internals/qemu-event-handlers.rst index 39094d793e..3589c4c48c 100644 --- a/src/qemu/EVENTHANDLERS.txt +++ b/docs/kbase/internals/qemu-event-handlers.rst @@ -1,10 +1,14 @@ +=================== +QEMU event handlers +=================== + This is a short description of how an example qemu event can be used to trigger handler code that is called from the context of a worker thread, rather than directly from the event thread (which should itself never block, and can't do things like send qemu monitor commands, etc). -In this case (the NIC_RX_FILTER_CHANGED event) the event is handled by +In this case (the ``NIC_RX_FILTER_CHANGED`` event) the event is handled by calling a qemu monitor command to get the current RX filter state, then executing ioctls/sending netlink messages on the host in response to changes in that filter state. This event is *not* propagated to the @@ -14,39 +18,39 @@ to the end of this document, please do!). Hopefully this narration will be helpful when adding handlers for other qemu events in the future. ----------------------------------------------------- +QEMU monitor events +------------------- Any event emitted by qemu is received by -qemu_monitor_json.c:qemuMonitorJSONIOProcessEvent(). It looks up the -event by name in the table eventHandlers (in the same file), which +``qemu_monitor_json.c:qemuMonitorJSONIOProcessEvent()``. It looks up the +event by name in the table ``eventHandlers`` (in the same file), which should have an entry like this for each event that libvirt -understands: +understands:: { "NIC_RX_FILTER_CHANGED", qemuMonitorJSONHandleNicRxFilterChanged, }, - NB: This table is searched with bsearch, so it *must* be - alphabetically sorted. +NB: This table is searched with bsearch, so it *must* be alphabetically sorted. -qemuMonitorJSONIOProcessEvent calls the function listed in -eventHandlers, e.g.: +``qemuMonitorJSONIOProcessEvent`` calls the function listed in +``eventHandlers``, e.g.:: qemu_monitor_json.c:qemuMonitorJSONHandleNicRxFilterChanged() which extracts any required data from the JSON ("name" in this case), -and calls: +and calls:: qemu_monitor.c:qemuMonitorEmitNicRxFilterChanged() -which uses QEMU_MONITOR_CALLBACK() to call -mon->cb->domainNicRxFilterChanged(). domainNicRxFilterChanged is one -in a list of function pointers in qemu_process.c:monitorCallbacks. For -our example, it has been set to: +which uses ``QEMU_MONITOR_CALLBACK()`` to call +``mon->cb->domainNicRxFilterChanged()``. ``domainNicRxFilterChanged`` is one +in a list of function pointers in ``qemu_process.c:monitorCallbacks``. For +our example, it has been set to:: qemuProcessHandleNicRxFilterChanged() -This function allocates a qemuProcessEvent object, and queues an event -named QEMU_PROCESS_EVENT_NIC_RX_FILTER_CHANGED (you'll want to add an -enum to qemu_domain.h:qemuProcessEventType for your event) for a +This function allocates a ``qemuProcessEvent`` object, and queues an event +named ``QEMU_PROCESS_EVENT_NIC_RX_FILTER_CHANGED`` (you'll want to add an +enum to ``qemu_domain.h:qemuProcessEventType`` for your event) for a worker thread to handle. (Everything up to this point has happened in the context of the thread @@ -56,17 +60,17 @@ monitor. Everything after this is handled in the context of a worker thread, so it has more freedom to make qemu monitor calls and blocking system calls on the host.) -When the worker thread gets the event, it calls +When the worker thread gets the event, it calls:: qemuProcessEventHandler() which switches on the eventType (in our example, -QEMU_PROCESS_EVENT_NIC_RX_FILTER_CHANGED) and decides to call: +``QEMU_PROCESS_EVENT_NIC_RX_FILTER_CHANGED``) and decides to call:: processNicRxFilterChangedEvent() and *that* is where the actual work will be done (and any -event-specific memory allocated during qemuProcessHandleXXX() will be +event-specific memory allocated during ``qemuProcessHandleXXX()`` will be freed). Note that this function must do proper refcounting of the domain object, and assure that the domain is still active prior to performing any operations - it is possible that the domain could have -- 2.35.3