[libvirt] [PATCH 3/5] qemu: Pass running reason to RESUME event handler

[Jiri Denemark]

On Wed, Sep 19, 2018 at 11:12:26 -0400, John Ferlan wrote:
> 
> 
> On 09/12/2018 08:55 AM, Jiri Denemark wrote:
> > Whenever we get the RESUME event from QEMU, we change the state of the
> > affected domain to VIR_DOMAIN_RUNNING with VIR_DOMAIN_RUNNING_UNPAUSED
> > reason. This is fine if the domain is resumed unexpectedly, but when we
> > sent "cont" to QEMU we usually have a better reason for the state
> > change. The better reason is used in qemuProcessStartCPUs which also
> > sets the domain state to running if qemuMonitorStartCPUs reports
> > success. Thus we may end up with two state updates in a row, but the
> > final reason is correct.
> > 
> > This patch is a preparation for dropping the state change done in
> > qemuMonitorStartCPUs for which we need to pass the actual running reason
> > to the RESUME event handler and use it there instead of
> > VIR_DOMAIN_RUNNING_UNPAUSED.
> > 
> > Signed-off-by: Jiri Denemark <jdenemar at redhat.com>
> > ---
> >  src/qemu/qemu_domain.h  |  4 ++++
> >  src/qemu/qemu_process.c | 23 +++++++++++++++++------
> >  2 files changed, 21 insertions(+), 6 deletions(-)
> > 
> > diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h
> > index 914c9a6a8d..3f3f7ccf18 100644
> > --- a/src/qemu/qemu_domain.h
> > +++ b/src/qemu/qemu_domain.h
> > @@ -366,6 +366,10 @@ struct _qemuDomainObjPrivate {
> >  
> >      /* counter for generating node names for qemu disks */
> >      unsigned long long nodenameindex;
> > +
> > +    /* qemuProcessStartCPUs stores the reason for starting vCPUs here for the
> > +     * RESUME event handler to use it */
> > +    virDomainRunningReason runningReason;
> 
> So what happens in the libvirtd restart case/condition?  This isn't
> Format/Parse'd so it's lost or essentially set to RUNNING_UNKNOWN.

Right, when libvirtd is restarted just after sending "cont", I don't
think we can expect to see the "RESUME" event in the new process. Most
likely the previous libvirtd process already got the event and just
didn't have a chance to process it. Thus just updating
qemuDomainObjPrivateXML{Parse|Format} to store this in the status XML
wouldn't help. We could add a code which would look at the restored
runningReason when seeing vCPUs are running, but status XML says the
domain is paused. But it would be in a separate patch anyway.

Jirka