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

[Ryan Harper <ryanh@us.ibm.com>]

* Anthony Liguori <aliguori@us.ibm.com> [2009-05-08 12:38]:
> Ryan Harper wrote:
> >* Anthony Liguori <aliguori@us.ibm.com> [2009-05-08 12:00]:
> >  

> >>If qemu_shutdown_requested(), then we'll immediately shutdown the system.
> >>    
> >
> >Right, but this request happens after we've sent the ACPI powerdown
> >event.  After we've done the powerdown (acpi aware guests can do a
> >shutdown), instead of then calling shutdown, which exits, we call
> >reset.
> >  
> 
> I'm saying, semantically, if you call 'qemu_shutdown_requested()', if it 
> returns 1, it means, immediately shutdown the VM--regardless of where 
> it's called.
> 
> The semantics of qemu_reboot_requested() are, if it returns 1, then only 
> when you see an ACPI soft power off, reset the VM.  It's that difference 
> in semantics that I think could lead to confusion.

well, I think this is where we're missing each other.  I figured if the
users requested a reboot, that we also trigger the powerdown, and that's
what I'm doing.  If in the monitor you issue system_reboot, I'm
triggering a powerdown automatically.  Are you saying you want the users
to do, system_reset, and then system_powerdown in their own?   And if
that is the case, I can see why you're asking to maintain the state of
the flag.  IMO, I think triggering the powerdown from the reboot call
makes sense.

> >>And I think this also needs to be stored as part of the savevm state for 
> >>hw/acpi.c.  If you do a system_reboot followed by an immediate live 
> >>migration, without the savevm handler, the VM will shutdown completely 
> >>after the migration instead of rebooting as expected.
> >>    
> >
> >Would it? I don't see that we are saving powerdown|shutdown|reset
> >request flags?  Sounds like all of those flags need to be in the save
> >state, and separate patch IMHO.
> >  
> 
> No, they don't.
> 
> A qemu_powerdown_request() call happens from the monitor.  This is to 
> allow a graceful shutdown (as opposed to exiting from the monitor).  
> This will trigger the TCG loop to immediately exit.  The state doesn't 
> need to be saved because you cannot do a migration in between when 
> qemu_powerdown_request() is called and when the shutdown actually happens.

Sure, and I don't see why reboot semantics would be any different unless
you thinking about the above case I think you might be meaning.


-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
ryanh@us.ibm.com