Re: [Xen-devel] [PATCH RFC 0/4] arm: regarding live migration

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2013-06-13 at 01:15 +0000, Jaeyong Yoo wrote:
> Hello Ian,
> I got some more questions while implementing live migration in arm.
> 
> > > (3) Regarding split drivers, come to think of it, we have to store 
> > >    both side (front/back) states, in-flight event channels, IRQs, etc.
> > >    And those look like quite a work (although evtchn is migrated within 
> > > vcpu)
> > >    I appreciate  if you guys could share any hints from the experience of 
> > >    migrating split drivers in x86.
> > 
> > There is no need to save any of this state, the devices are effectively
> > reconnected from scratch on the destination and the frontend devices are
> > responsible for replaying any inflight state on resume.
> > 
> 
> I'm trying to find the suspending part of PV driver, but can not locate it.
> (And, looks like there is no function like suspend in xen-blkfront.c)
> One guess is by deleting vbd in xenstore, maybe hot-plug-out can suspend.
> Could you give me some advice?

IIRC this is all handled by the block driver on resume and no work is
required on suspend. Essentially it simply replays the ring on resume. I
think it is done this way so that in checkpoint type saves the resume of
the original domain after checkpointing is cheap because nothing needs
to be done.

> And, about grant table, if we effectively suspend and resume PV driver, I 
> think we don't need to migrate grant table entires. Is this right?

Correct.

Ian.


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