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

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

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On 2011-07-28 19:48, Luiz Capitulino wrote:
> On Thu, 28 Jul 2011 14:39:23 -0300
> Luiz Capitulino <lcapitulino@redhat.com> wrote:
> 
>> On Thu, 28 Jul 2011 17:20:41 +0200
>> Jan Kiszka <jan.kiszka@web.de> wrote:
>>
>>> 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.
>>
>> The only permanent vm_stop we'd have is poweroff when -no-shutdown is used.
>>
>> Are you saying that system_reset should be able to recover from that too?
> 
> It already does, so we don't have permanent stops.

Exactly. We just have stops over inconsistent states that require a
reset to continue with anything useful.

Jan


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