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

[Anthony Liguori <aliguori@us.ibm.com>]

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.

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

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.

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.

-- 
Regards,

Anthony Liguori