Re: [Qemu-devel] [RFC] Introduce vm_stop_permanent()

[Jan Kiszka <jan.kiszka@web.de>]

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On 2011-07-28 17:18, Luiz Capitulino wrote:
> 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)...

But the right point for reset is start, not stop. Otherwise we loose the
state before the stop.

Jam


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