[Xen-devel]How could Xen know a certain GuestOS have already shutdown?

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[Xen-devel]How could Xen know a certain GuestOS have already shutdown?

Bruce Granger
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Hi everyone! This is probably a familiar problem, but I haven't found anything in the archives or from google yet. I also talked with my parterners but we haven't got a sure conclusion. Recently I’m caring about a question about shutdown operation: When we shutdown a GuestOS by giving the command in its terminal, how can hypervisor get to know that this GuestOS is about to shutdown and How can hypervisor know that GuestOS has already done the work of shutdown? In other word, is there any signal or something else that GuestOS deliver to hypervisor to notice that it will shutdown or it has accomplished its shutdown work? Does anyone know the detailed process? Thanks for your help!
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Re: [Xen-devel]How could Xen know a certain GuestOS have already shutdown?

Bruce Granger
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It's my honor to receive your answer! Thanks very much!
I have learned much more under your guidance,but I still have a little question!
I've traced the VIRQ_DOM_EXC which  send from Xen to Dom0 and picked up by xenstored which fires the @releaseDomain watch when a GuestOS start to shutdown.

Here, I still have two questions.
First, I haven't found anything useful in the archives about 'releaseDomain watch'.What is the called '@releaseDomain' ? what's the use of it?
Second,I think that VIRQ_DOM_EXC is the signal used for communicate between hypervisor and Dom0. I talked that with my parterner, we think that when shutdown occurs, GuestOS will first get in touch with hypervisor ,then cause the communication between Xen and Dom0 by VIRQ_DOM_EXC,is that right? What we also want to know is when shutdown operation occurs in GuestOS, how GuestOS communicate with the hypervisor first? Is there any signal or somehow event delivery?
Could you tell me more about that?

Thanks a lot!