Re: [Xen-devel] suspend operation in XEND

[Nauzad Sadry <nauzad@xxxxxxxxx>]

when the domainU is being suspended I see "shutdown_suspend_t" message
sent to the domain thru the event channel by XEND.

what does the domainU do on receiving this message ??

is the DISCONNECTED message sent by XEND as a part of suspend_domain
or as a part of destroy_domain??

Thanks,

Nauzad

On Fri, 21 Jan 2005 00:28:46 +0000, Mark Williamson <maw48@xxxxxxxxxxxx> wrote:
> > So when does the event channel between the backend & front end drivers
> > break during suspend operation in XEND ??
> 
> The event channel itself will get destroyed when the domain is destroyed
> (after the domain's contents are saved).  From the guests PoV, no teardown of
> event channels or shared memory occurs before suspend - it all gets sorted
> out on resume.
> 
> > Also when is the NETIF_INTERFACE_STATUS_DISCONNECTED status sent to
> > the front-end driver? I see code in the front-end driver that
> > processes this status type which results in the front-driver going to
> > a suspend state (like unregistering IRQs etc)
> 
> Interfaces go through various states.  During normal operation, these look
> like the following:
> * DISCONNECTED -> CLOSED -> CONNECTED when an interface is attached to the
> domain
> * CONNECTED -> CLOSED -> DISCONNECTED when an interface is removed.  In this
> case, the interface is in the CLOSED state when the DISCONNECTED message
> arrives, so this is the final disconnect for the interface
> 
> If the interface is in the CONNECTED state and a DISCONNECTED message is
> received, it means that the connection with the backend has been broken for
> some reason (e.g. the domain migrated to a new host, the backend driver
> domain was rebooted, etc).  When this happens, Xend will send this message to
> the domain.
> 
> If the guest sees this then it must go through the DISCONNECTED -> CLOSED ->
> CONNECTED transition again, talking on the control interface to set up shared
> memory and bind event channels with the new backend.  At this point, it also
> frees resources associated with the old device channel that are no longer
> needed (e.g. old IRQs).
> 
> HTH,
> Mark
> 
> > On Thu, 20 Jan 2005 22:54:25 +0000, Mark Williamson <maw48@xxxxxxxxxxxx>
> wrote:
> > > > During Save & Migration, XFRD sends "xfr.suspend" message to XEND.
> > > > This results in XEND suspending the domainU. A part of the suspension
> > > > should involve XEND sending DISCONNECT message to the front-end driver
> > > > in domainU
> > >
> > > I don't think you'll find it.  Migrations / suspensions are treated like
> > > a backend driver restart - at resume the frontend driver is notified that
> > > it needs to reconnect to the backend and is responsible for requeuing any
> > > pending requests.
> > >
> > > Instead of explicitly disconnecting the domain at suspend, the frontend
> > > driver just sorts everything out at resume.
> > >
> > > Cheers,
> > > Mark
> > >
> > > > I am trying to dig through the XEND python code & I am unable to find
> > > > this information. Can someone help ??
> > > >
> > > > Also can someone guide me through the set of functions that are called
> > > > by XEND as a part of suspend. What is the use of the the
> > > > domain_restart_schedule() ??
> > > >
> > > > Thanks
> > > >
> > > > Nauzad
> > > >
> > > >
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