[libvirt PATCH v3 00/21] Add support for persistent mediated devices
eskultet at redhat.com
Thu Jan 7 16:50:10 UTC 2021
On Thu, Dec 24, 2020 at 08:14:24AM -0600, Jonathon Jongsma wrote:
> This patch series follows the previously-merged series which added support for
> transient mediated devices. This series expands mdev support to include
> persistent device definitions. Again, it relies on mdevctl as the backend.
> It follows the common libvirt pattern of APIs by adding the following new APIs
> for node devices:
> - virNodeDeviceDefineXML() - defines a persistent device
> - virNodeDeviceUndefine() - undefines a persistent device
> - virNodeDeviceCreate() - starts a previously-defined device
> It also adds virsh commands mapping to these new APIs: nodedev-define,
> nodedev-undefine, and nodedev-start.
> Since we rely on mdevctl for the definition of ediated devices, we need a way
> to stay up-to-date with devices that are defined by mdevctl (outside of
> libvirt). The method for staying up-to-date is currently a little bit crude
> due to the fact that mdevctl does not emit any events when new devices are
> added or removed. As a workaround, we create a file monitor for the mdevctl
> config directory and re-query mdevctl when we detect changes within that
> directory. In the future, mdevctl may introduce a more elegant solution.
> changes in v3:
> - streamlined tests -- removed some unnecessary duplication
> - split out patch to factor out node device name generation function
> - split nodeDeviceParseMdevctlChildDevice() into a separate function
> - added follow-up patch to remove space-padded alignment in header
> - refactored the mdevctl update handling significantly:
> - no longer a separate persistent thread that gets signaled by a timer
> - now piggybacks onto the existing udev thread and signals the thread in t=
> same way that the udev event does.
> - Daniel suggested spawning a throw-away thread to handle mdevctl updates,
> but that introduces the complexity of possibly serializing multiple
> throw-away threads (e.g. if we get an 'created' event followed immediate=
> by a 'deleted' event, two threads may be spawned and we'd need to ensure
> they are properly ordered)
> - added virNodeDeviceObjListForEach() and virNodeDeviceObjListRemoveLocked()
> to simplify removing devices that are removed from mdevctl.
> - coding style fixes
> - NOTE: per Erik's request, I experimented with changing the way that mdevctl
> commands were generated and tested (e.g. introducing something like
> virMdevctlGetCommand(def, MDEVCTL_COMMAND_<SUBCOMMAND>, ...)), but it was
> too invasive and awkward and didn't seem worthwhile
Thanks for giving ^this a try :)
I think we're converging nicely with the only remaining bit to agree on being
the mdevctl monitoring thread. I think we can target 7.1.0 with this series.
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