On Mon, Apr 29, 2024 at 05:06:36PM +0200, Philippe Mathieu-Daudé wrote: > Hi, > > On 29/4/24 00:25, Philippe Mathieu-Daudé wrote: > > Hi, > > > > The KVM/QEMU community call is at: > > > > https://meet.jit.si/kvmcallmeeting > > @ > > 30/4/2024 14:00 UTC > > > > Are there any agenda items for the sync-up? > > I'd like to discuss two issues: > > 1/ Stability of QOM path > --------------------- > > Currently we have 3 QOM containers: > - /machine > QOM objects properly parented go there > - /machine/unattached > Orphan QOM objects. Missing parent is usually easy > to figure out, but we need to post patches to fix them. > - /machine/peripheral[-anon] > Devices created at runtime with CLI -device or QAPI device_add. > (-anon is for devices with no explicit bus ID). > See "Problem 4: The /machine/unattached/ orphanage" in [1]. > > The /machine and /machine/unattached trees are stable, although > by adding parent to orphan objects, their path will change. > > Objects in /machine/peripheral[-anon] depend on the order of > the device_add commands / arguments used. > > In a dynamically created machine, everything depend on how the > device_add commands are processed. > > How can be expect to easily reference a QOM object by its path?
FYI, for reference libvirt uses a couple of QOM paths * "/machine/unattached/device[0]" - path of first vCPU, but this is an historical artifact - nowdays we query the paths from query-cpus-fast * "/machine/peripheral/%s/virtio-backend" where '%s' is the ID we give the virtio device, for virtio-blk disks * /machine/peripheral/%s/%s.0/legacy[0] where both '%s' are the ID we give the USB defvice, for USB disks * /machine/peripheral when enumerating devices we've assigned ID aliases to. * /machine to get the rtc-time property value > 2/ Is it safe to broadcast a QAPI event to all type of device/object? > ------------------------------------------------------------------ > > We have QMP commands such @rtc-reset-reinjection or @inject-nmi > which expect a single RTC / NMI listener in the machine. > > When using heterogeneous machines, we might end with multiple RTC > or NMI-aware devices. Should these commands be broadcasted to all > devices, or should we explicitly pass a list of paths to devices > we want to notify. Maybe we want both options. > > See threads around NMI [2] and RTC [3]. > > [1] https://lore.kernel.org/qemu-devel/87o7d1i7ky....@pond.sub.org/ > [2] > https://lore.kernel.org/qemu-devel/f4a6492b-cff4-439d-8f34-cdf04cb74...@redhat.com/ > [3] > https://lore.kernel.org/qemu-devel/20240425133745.464091-1-d-tatia...@yandex-team.ru/ > > Regards, > > Phil. > With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
