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Date: Thu, 28 Jul 2011 12:18:11 -0300
From: Luiz Capitulino <lcapitulino@redhat.com>
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Subject: Re: [Qemu-devel] [RFC] Introduce vm_stop_permanent()
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To: Jan Kiszka <jan.kiszka@web.de>
Cc: Blue Swirl <blauwirbel@gmail.com>, Avi Kivity <avi@redhat.com>, qemu-devel <qemu-devel@nongnu.org>

On Thu, 28 Jul 2011 16:19:19 +0200
Jan Kiszka <jan.kiszka@web.de> wrote:

> On 2011-07-28 15:37, Avi Kivity wrote:
> > On 07/28/2011 04:31 PM, Luiz Capitulino wrote:
> >> On Thu, 28 Jul 2011 10:23:22 +0300
> >> Avi Kivity<avi@redhat.com>  wrote:
> >>
> >> >  On 07/28/2011 12:44 AM, Blue Swirl wrote:
> >> >  >  On Wed, Jul 27, 2011 at 9:42 PM, Luiz
> >> Capitulino<lcapitulino@redhat.com>   wrote:
> >> >  >  >   This function should be used when the VM is not supposed to
> >> resume
> >> >  >  >   execution (eg. by issuing 'cont' monitor command).
> >> >  >  >
> >> >  >  >   Today, we allow the user to resume execution even when:
> >> >  >  >
> >> >  >  >     o the guest shuts down and -no-shutdown is used
> >> >  >  >     o there's a kvm internal error
> >> >  >  >     o loading the VM state with -loadvm or "loadvm" in the
> >> monitor fails
> >> >  >  >
> >> >  >  >   I think only badness can happen from the cases above.
> >> >  >
> >> >  >  I'd suppose a system_reset should bring the system back to
> >> sanity and
> >> >  >  then clear vm_permanent_stopped (where's -ly?)
> >>
> >> What's -ly?
> >>
> > 
> > permanent-ly.
> > 
> >> >  >  except maybe for KVM
> >> >  >  internal error if that can't be recovered. Then it would not very
> >> >  >  permanent anymore, so the name would need adjusting.
> >> >
> >> >  Currently, all kvm internal errors are recoverable by reset (and
> >> >  possibly by fiddling with memory/registers).
> >>
> >> Ok, but a poweroff in the guest isn't recoverable with system_reset
> >> right? Or does it depend on the guest?
> > 
> > Right, it's not recoverable if you shut the power down where the tractor
> > beam is coupled to the main reactor.
> 
> system_reset will bring all emulated devices back into their power-on
> state - unless we have remaining bugs to fix. Actually, one may consider
> issuing this reset automatically on vm_start after "permant" vm_stop.

I'm going to abandon the vm_stop_permanent() idea.

I'm thinking something towards having a stop_kind argument to vm_stop(),
which could be temporary (which is what we have today), only with
system_reset or permanent.

Or maybe vm_stop_opt(), which allows for fine grained control of stop
(vm_stop() would default to today's behavior)...