Re: [Qemu-devel] [PATCH][RESEND] Add monitor command for system_reboot

[Amit Shah]

On (Thu) Jul 16 2009 [15:39:59], Jamie Lokier wrote:
> Amit Shah wrote:
> > On (Wed) Jul 08 2009 [19:02:16], Avi Kivity wrote:
> > > On 07/08/2009 06:43 PM, Ryan Harper wrote:
> > >>> That suffers from the same problem as a system_reboot command in that
> > >>> the guest may never start the shutdown. If that's an acceptable
> > >>> limitation, then we might as well implement it directly in QEMU as
> > >>> system_reboot so its easily available to everyone. Make 'system_reboot'
> > >>> take an optional timeout arg (default to 60 seconds) after which it
> > >>> cancels its plans.
> > >>>      
> > >>
> > >> This seems the most reasonable thing to me.  As already mentioned,
> > >> system_powerdown already is non-deterministic since the guest could
> > >> ignore the ACPI event.
> > >>    
> > >
> > > It could also send the guest to sleep or initiate the self destruct  
> > > sequence.  I don't think we should press the power button unless the  
> > > user explicitly asked us to.  This means we'll need a guest agent like 
> > > Xen.
> > 
> > This is another use-case for vmchannel (or virtio-serial) where  the user
> > exists within qemu.
> 
> What happens then the guest is non-responsive because it crashed, or
> the agent isn't working, or the guest doesn't support virtio?

In the first two cases it has to be forced (as for a physical machine).
The last case can be detected before using any virtio-serial
functionality.

> Some way to override the guest is needed for all reboot/powerdown options.

Sure, just that a PV reboot/powerdown option is more reliable if the
guest ignores the ACPI events.

> "kill -9 $(pidof kvm)" is really unacceptable, but I've had to do it
> on several occasions unfortunately.
> 
> Ideally, an option to those commands "--force" to ignore the guest and
> just do it, and an option like "--timeout-force=5" to behave like
> holding down the power button on a real computer.
> 
> (It would be nice to be able to change the value of -no-shutdown and
> -no-reboot from the monitor, too.)
> 
> -- Jamie

                Amit