RE: [Xen-users] Any difference between live migrating of para-virtualized and full-virtualized domains?

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Mark Williamson
> Sent: 10 February 2007 11:49
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Cc: Liang Yang
> Subject: Re: [Xen-users] Any difference between live 
> migrating of para-virtualized and full-virtualized domains?
> 
> > I'm just wondering if Xen treats para-virtualized and 
> full-virtualized
> > domain differently when doing live migration?
> 
> The process is similar, but there's a different set of state 
> to be migrated.  
> Also, PV guests participate more actively in the migration 
> than FV guests do.
> 
> I'm not sure if FV live migration is in mainline yet.  I'd 
> imagine they're 
> pretty similar from the user's point of view.

FV (HVM) save/restore is currently working (although there are probably
a few reliability bugs - after a few hundred save/restore cycles, the
guest may crash). [There's been a couple of patches since I tried it
last time, so it is possible that it's been fixed - although none of the
patches mentions "fixes reliability", so it would be a "chance fix",
rather than a "intentional fix" in that case]. 

Live migration is a bit further in the future, as it relies on
"Log-dirty" to track the pages that have been written to since the
original copy of the pages. Since this feature isn't in the
shadow-paging code that HVM uses, it's not going to work until log-dirty
is supported, which is unknown when this will happen. 

Currently live-migration aborts in xc_hvm_save() with a message of
"can't do live migration" (or something like that) - but removing that
error message wouldn't REALLY fix anything, as log-dirty is still not
working.

As Mark says, xm save/restore/migrate should be exactly the same for
both types of domains, so the user doesn't need to know whether it's a
PV or FV domain that is being saved/restored/migrated. 

--
Mats


> 
> Cheers,
> Mark
> 
> -- 
> Dave: Just a question. What use is a unicyle with no seat?  
> And no pedals!
> Mark: To answer a question with a question: What use is a skateboard?
> Dave: Skateboards have wheels.
> Mark: My wheel has a wheel!
> 
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