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Re: Live migration and PV device handling

On Fri, Apr 3, 2020 at 6:44 AM Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
> On 03/04/2020 13:32, Anastassios Nanos wrote:
> > Hi all,
> >
> > I am trying to understand how live-migration happens in xen. I am
> > looking in the HVM guest case and I have dug into the relevant parts
> > of the toolstack and the hypervisor regarding memory, vCPU context
> > etc.
> >
> > In particular, I am interested in how PV device migration happens. I
> > assume that the guest is not aware of any suspend/resume operations
> > being done
> Sadly, this assumption is not correct.  HVM guests with PV drivers
> currently have to be aware in exactly the same way as PV guests.
> Work is in progress to try and address this.  See
> https://xenbits.xen.org/gitweb/?p=xen.git;a=commitdiff;h=775a02452ddf3a6889690de90b1a94eb29c3c732
> (sorry - for some reason that doc isn't being rendered properly in
> https://xenbits.xen.org/docs/ )

That proposal is very interesting - first time it came across my radar
- but I dislike the idea that domain IDs need to be preserved for
uncooperative migration to work. Ideally I would be able to take
advantage of the same plumbing to perform forking of VMs with PV
drivers where preserving the domain id is impossible since its still
in use.




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