Re: [libvirt] [PATCH 3/6] fix migration of paused vms upon failure
Paolo Bonzini wrote:
This makes a small change on the failed-migration path. Up to now,
all VMs that failed non-live migration after the "stop" command
were restarted. This must not be done when the VM was paused in
the first place.
OK, yes, after thinking about this, I agree with this semantic. However, I
don't really agree with the implementation below. Here's why:
If your domain is already paused, then you'll be issuing a
"qemuMonitorStopCPUs"
command unnecessarily. That by itself isn't a huge deal; it will essentially be
a no-op. But you will also generate an event of "VIR_DOMAIN_EVENT_SUSPENDED",
which is wrong; you didn't really suspend the domain, an earlier command did. I
think the implementation should be something more along the lines of:
paused = 0;
if (!(flags & VIR_MIGRATE_LIVE) && vm->state == VIR_DOMAIN_RUNNING) {
stop_cpus();
generate_event();
paused = 1;
vm->state = PAUSED;
}
Make sense?
One other thing to possibly investigate is whether the "vm->state ==
VIR_DOMAIN_RUNNING" is sufficient. Can we (legitimately) be in state
VIR_DOMAIN_NOSTATE or VIR_DOMAIN_BLOCKED, yet still be "running"? I'm not
sure,
but I'd want to make sure before using that as a condition.
--
Chris Lalancette