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Re: [Qemu-devel] wake-on-lan & IPMI implementation; real power-off and -


From: Anthony Liguori
Subject: Re: [Qemu-devel] wake-on-lan & IPMI implementation; real power-off and -no-shutdown
Date: Mon, 15 Mar 2010 11:29:13 -0500
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.5) Gecko/20091209 Fedora/3.0-4.fc12 Lightning/1.0pre Thunderbird/3.0

On 03/15/2010 10:55 AM, Daniel P. Berrange wrote:
On Mon, Mar 15, 2010 at 04:01:27PM +0100, Fran?ois Revol wrote:
Hello,
while working on a demonstrator for a green-IT project, to show
scheduled machine shutdown and powering depending on various
conditions, I wondered if I could use QEMU with wake-on-lan
transparently, but it seems it's not implemented at all.

I though I could try to add support for it, and with -S it theorically
should be doable at least for the first boot, but the network packets
do not go much further until the NIC is actually initialized, as most
network layers use qemu_can_send_packet() which returns 0 if the
machine is stopped.
Hacking this function to return 1 seems to push the packet upward, but
I couldn't find a single point where I could check for WOL packets,
different -net subsystems using different code paths.

Also, it seems -no-shutdown doesn't actually "stop the emulation" as
said in the manual, it actually keeps the vm running (and using cpu),
despite the OS trying to shutdown via ACPI. At least I tested so with
Haiku (and acpi=true in kernel config), which properly exits QEMU
without -no-shutdown.
Hmm, I think -no-shutdown should at least stop the CPUs executing. It is
not really useful on its own though. The app managing QEMU would want to
use the new JSON based monitor to listen for the SHUTDOWN event to be
emitted, so it can detect the shutdown completing&  then take action it
wants either reset the guest, or kill QEMU, etc

The semantics of -no-shutdown are awful.

I'd personally prefer to see the option deprecated and a new set of options introduced with clearer semantics.

Currently, -no-shutdown does too many things. It affects reboot behaviour, shutdown behaviour, the behavior of the SDL close button. Each of these things should be individual tunables.

Regards,

Anthony Liguori

Daniel





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