On Jan 8, 2013, at 1:30 PM, "Daniel P. Berrange" <berra...@redhat.com> wrote:
> On Tue, Jan 08, 2013 at 01:28:10PM -0500, Andres Lagar-Cavilla wrote: >> On Jan 7, 2013, at 5:44 PM, "Daniel P. Berrange" <berra...@redhat.com> wrote: >> >>> On Mon, Jan 07, 2013 at 04:25:01PM -0500, Andres Lagar-Cavilla wrote: >>>> Perform all the appropriate plumbing. >>>> >>>> When qemu/KVM VMs are paused manually through a monitor not-owned by >>>> libvirt, >>>> libvirt will think of them as "paused" event after they are resumed and >>>> effectively running. With this patch the discrepancy goes away. >>>> >>>> This is meant to address bug 892791. >>>> >>>> Signed-off-by: Andres Lagar-Cavilla <and...@lagarcavilla.org> >>> >>> Although we don't support people issuing monitor commands behind >>> libvirt's back, I see no harm in handling the resume event here, >>> as long as we don't end up emitting multiple resume events for >>> a single operation (eg if libvirt triggers the resume it already >>> emits an event independently) >> >> Hi Daniel, >> >> In most cases, qemuProcessStartCPUs will be the libvirt API issuing qemu >> 'cont' commands. Due to the locking rules, we can be confident that it will >> complete processing while holding the VM lock, and in the process update the >> state to VIR_DOMAIN_RUNNING. The callback handler for RESUME introduced here >> will be serialized against the VM lock after StartCPUs, and result in >> effectively a no-op (because it only does work if the vm state is PAUSED). >> >> Create/Load Snapshot call StopCPUs before doing any work, so qemu itself >> will not attempt to resume the VM, and thus no event will be generated. In >> strict terms this is unnecessary (although relatively little) work, but here >> is the rationale in qemu_driver.c: >> /* savevm monitor command pauses the domain emitting an event which >> * confuses libvirt since it's not notified when qemu resumes the >> * domain. Thus we stop and start CPUs ourselves. >> */ >> >> Relevant to the issue at hand. If this patch is merged then the library >> can get rid of this StopCPUs invocation, but additional book-keeping is >> necessary. IMHO this is neither pressing nor necessary. > > Actally we can't get rid of it, because events only work in QMP mode. > If talking to an old QEMU via HMP we need to deal with it as described > in the comment. > > > ACK to your patch anyway. Cool, thanks. Not sure about the process around here. More ACKs needed? Andres > > Daniel > -- > |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| > |: http://libvirt.org -o- http://virt-manager.org :| > |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| > |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
