[libvirt] [PATCH] qemu: Rework handling of shutdown event

[Daniel P. Berrange]

On Fri, Dec 02, 2011 at 09:22:37AM -0700, Eric Blake wrote:
> On 12/02/2011 08:02 AM, Jiri Denemark wrote:
> > When QEMU guest finishes its shutdown sequence, qemu stops virtual CPUs
> > and when started with -no-shutdown waits for us to kill it using
> > SGITERM. Since QEMU is flushing its internal buffers, some time may pass
> > before QEMU actually dies. We mistakenly used "paused" state (and
> > events) for this which is quite confusing since users may see a domain
> > going to pause while they expect it to shutdown. Since we already have
> > "shutdown" state with "the domain is being shut down" semantics, we
> > should use it for this state.
> > 
> > However, the state didn't have a corresponding event so I created one
> > and called its detail as VIR_DOMAIN_EVENT_SHUTDOWN_FINISHED (guest OS
> > finished its shutdown sequence) with the intent to add
> > VIR_DOMAIN_EVENT_SHUTDOWN_STARTED in the future if we have a
> > sufficiently capable guest agent that can notify us when guest OS starts
> > to shutdown.
> 
> Not for this patch, but should we use VIR_DOMAIN_EVENT_SHUTDOWN_STARTED
> any time we use the virDomainShutdown API to request a graceful
> shutdown?  That is, by actually changing the state of the domain after a
> call to virDomainShutdown, it will be more apparent whether a user has
> previously requested shutdown, and if the guest is still running, it
> means the guest either didn't react to the ACPI interrupt or else is
> taking a long time to shut down.

I don't think we should do this in the lifecycle events. Not least because
emitting "VIR_DOMAIN_EVENT_SHUTDOWN_STARTED" would be very misleading because
a guest OS is free to ignore the ACPI power event. The lifecycle events
should only reflect things that have actually happened to the guest VM
lifecycle & I don't really this counts.
 
Daniel
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