[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 12:00]:
> Ryan Harper wrote:
> >Add a new monitor command (system_reboot) for a soft reboot which uses
> >system_powerdown to trigger ACPI shutdown in the guest and once shutdown is
> >complete, trigger a reset instead of exiting qemu.
> >
> >Depends on commit a6d6552426dcbf726e5549f08b70c9318d6be14b which enabled 
> >ACPI
> >power button support.
> >
> >Tested with Ubuntu 9.04 64-bit guest.
> >
> >Signed-off-by: Ryan Harper <ryanh@us.ibm.com>
> >
> >diff --git a/hw/acpi.c b/hw/acpi.c
> >index dbaf18a..346d100 100644
> >--- a/hw/acpi.c
> >+++ b/hw/acpi.c
> >@@ -151,7 +151,13 @@ static void pm_ioport_writew(void *opaque, uint32_t 
> >addr, uint32_t val)
> >                 sus_typ = (val >> 10) & 7;
> >                 switch(sus_typ) {
> >                 case 0: /* soft power off */
> >-                    qemu_system_shutdown_request();
> >+                    /* after powerdown, if on system_reboot path, call 
> >reset +                       instead of shutdown */
> >+                    if (qemu_reboot_requested()) {
> >+                        qemu_system_reset_request();
> >+                    } else {
> >+                        qemu_system_shutdown_request();
> >+                    }
> >                     break;
> >  
> 
> 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.

> 
> qemu_reboot_requested() has different semantics, it's really a soft 
> request.  I think the name needs to reflect that.

Not sure what you mean here.

> 
> Also, the soft reset flag ought to get reset whenever a VM changes it's 
> state.  That is, if you do a system_reboot, then a system_reset (imagine 
> that the reboot fails), then you do a normal powerdown in the guest, 
> instead of shutting off like the user would expect, we'll reboot because 
> the qemu_reboot_requested() is still true.
> 
> A good way to do that would be by registering a reset handler in 
> hw/acpi.c.  In fact, I think that the whole functionality probably 
> should live in hw/acpi.c.

OK

> 
> 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.

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